ENDOGEN INC
SC 14D1, 1999-06-02
IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES
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<PAGE>
________________________________________________________________________________
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------

                                 SCHEDULE 14D-1
              TENDER OFFER STATEMENT PURSUANT TO SECTION 14(d)(1)
                                     OF THE
                        SECURITIES EXCHANGE ACT OF 1934
                                      AND
                                  SCHEDULE 13D
                   UNDER THE SECURITIES EXCHANGE ACT OF 1934
                            ------------------------

                                 ENDOGEN, INC.
                           (Name of Subject Company)

                             EWOK ACQUISITION CORP.
                               PERBIO SCIENCE AB
                                  PERSTORP AB
                                   (Bidders)

                         COMMON STOCK, PAR VALUE $0.01
                         (Title of Class of Securities)

                                  29264J 10 8
                     (CUSIP Number of Class of Securities)

                                MAGNUS LINDQUIST
                            CHIEF FINANCIAL OFFICER
                                  PERSTORP AB
                           SE-284 80 PERSTORP, SWEDEN
                               011-46-435-380-00
                            ------------------------

                                   COPIES TO:
                          PATRICIA KAVEE MELICK, ESQ.
                                 WIGGIN & DANA
                              THREE STAMFORD PLAZA
                          STAMFORD, CONNECTICUT 06911
                                 (203) 363-7600

          (Name, Address and Telephone Number of Persons Authorized to
            Receive Notices and Communications on Behalf of Bidders)

                                  MAY 27, 1999
        (Date of Event which Requires Filing Statement on Schedule 13D)
                            ------------------------

                           CALCULATION OF FILING FEE

<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------
                 <S>                                                       <C>
                 TRANSACTION VALUATION*                                    AMOUNT OF FILING FEE*
- ------------------------------------------------------------------------------------------------------------------
                     $14,767,882.50                                              $2,953.58
- ------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------
</TABLE>

* For purposes of calculating amount of filing fee only. This amount assumes the
  purchase of 3,938,102 shares of Common Stock, par value $0.01 (the 'Shares'),
  at a price per Share of $3.75 in cash. Such number of Shares represents all
  the Shares outstanding as of May 26, 1999, plus the number of Shares issuable
  upon the exercise of all outstanding vested in-the-money options and warrants.

[ ] Check box if any part of the fee is offset as provided by Rule 0-11(a)(2)
    and identify the filing with which the offsetting fee was previously paid.
    Identify the previous filing by registration statement number, or the Form
    or Schedule and the date of its filing.

<TABLE>
<S>                                          <C>
AMOUNT PREVIOUSLY PAID:                       FILING PARTY:
FORM OR REGISTRATION NO.:                     DATE FILED:
</TABLE>

________________________________________________________________________________

<PAGE>
<TABLE>
        <S>    <C>                                                                                   <C>
         1     NAMES OF REPORTING PERSONS
               IRS IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
               Ewok Acquisition Corp.
         2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                                     (a) [x]
                                                                                                     (b) [ ]
         3.    SEC USE ONLY
         4.    SOURCE OF FUNDS*
               AF
         5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
               TO ITEM 2(e) or 2(f)                                                                      [ ]
         6.    CITIZENSHIP OR PLACE OF ORGANIZATION
               Massachusetts
         NUMBER OF
          SHARES
       BENEFICIALLY
         OWNED BY
           EACH
         REPORTING
        PERSON WITH
                       7.    SOLE VOTING POWER                          0
                       8.    SHARED VOTING POWER                        1,259,772
                       9.    SOLE DISPOSITIVE POWER                     0
                      10.    SHARED DISPOSITIVE POWER                   1,259,772
        11.    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
               1,259,772
        12.    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
               CERTAIN SHARES*                                                                           [ ]
        13.    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
               30.3%
        14.    TYPE OF REPORTING PERSON*
               CO
</TABLE>


                          *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                           2


<PAGE>


<TABLE>

        <S>    <C>                                                                                   <C>

         1.    NAMES OF REPORTING PERSONS
               IRS IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
               PerBio Science AB
         2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                                     (a) [x]
                                                                                                     (b) [ ]
         3.    SEC USE ONLY
         4.    SOURCE OF FUNDS*
               AF
         5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
               TO ITEM 2(e) or 2(f)                                                                      [ ]
         6.    CITIZENSHIP OR PLACE OF ORGANIZATION
               Sweden
         NUMBER OF
          SHARES
       BENEFICIALLY
         OWNED BY
           EACH
         REPORTING
        PERSON WITH
                       7.    SOLE VOTING POWER                          0
                       8.    SHARED VOTING POWER                        1,259,772
                       9.    SOLE DISPOSITIVE POWER                     0
                      10.    SHARED DISPOSITIVE POWER                   1,259,772
        11.    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
               1,259,772
        12.    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
               CERTAIN SHARES*                                                                           [ ]
        13.    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
               30.3%
        14.    TYPE OF REPORTING PERSON*
               CO
</TABLE>

                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                       3

<PAGE>
<TABLE>
        <S>   <C>                                                                                   <C>
         1.    NAMES OF REPORTING PERSONS
               IRS IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
               Perstorp AB
         2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                                     (a) [x]
                                                                                                     (b) [ ]
         3.    SEC USE ONLY
         4.    SOURCE OF FUNDS*
               WC
         5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
               TO ITEM 2(e) or 2(f)                                                                      [ ]
         6.    CITIZENSHIP OR PLACE OF ORGANIZATION
               Sweden
         NUMBER OF
          SHARES
       BENEFICIALLY
         OWNED BY
           EACH
         REPORTING
        PERSON WITH
                      7.    SOLE VOTING POWER                         0
                      8.    SHARED VOTING POWER                       1,259,772
                      9.    SOLE DISPOSITIVE POWER                    0
                     10.    SHARED DISPOSITIVE POWER                  1,259,772
        11.    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
               1,259,772
        12.    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
               CERTAIN SHARES*                                                                           [ ]
        13.    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
               30.3%
        14.    TYPE OF REPORTING PERSON*
               CO
</TABLE>

                             *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                                4




<PAGE>
                                EXPLANATORY NOTE

     On May 27, 1999, PerBio Science AB ('Parent') and EWOK Acquisition Corp., a
wholly owned subsidiary of Parent (the 'Purchaser'), entered into a Stockholder
Agreement (the 'Stockholder Agreement'), with Owen A. Dempsey, the President and
Chief Executive Officer of Endogen, Inc. (the 'Company'), Hayden H. Harris,
Chairman of the Board, Charles R. Burke, Christine A. Burns, Avery W. Catlin,
Wallace G. Dempsey, Irwin J. Gruverman, G&G Diagnostics Limited Partnership I,
Hayden H. Harris Living Trust DTD 3/6/98 and Wolfgang Woloszczuk (collectively,
the 'Selling Stockholders'), pursuant to which such Selling Stockholders have
agreed to tender to the Purchaser, and the Purchaser has agreed to purchase, all
of the shares of Company Common Stock, $.01 par value (the 'Shares'),
beneficially owned by them, including 569,600 shares currently outstanding which
represent approximately 16% of the Shares issued and outstanding, plus Shares
subsequently acquired by a Selling Stockholder through the exercise of options
or otherwise, at a price per Share equal to $3.75, provided that such obligation
to tender and such obligation to purchase are subject to certain conditions,
including the Minimum Condition (as defined in the Offer to Purchase (as
hereinafter defined)), having been satisfied and the Purchaser having accepted
Shares for payment under the Offer (as hereinafter defined). Pursuant to the
Stockholder Agreement, each Selling Stockholder has also executed and delivered
a proxy for the benefit of the Purchaser with respect to the Shares subject to
the Stockholder Agreement owned by such Selling Stockholder to vote such Shares
against certain competing transactions, as more fully described in Section 12
'The Merger Agreement; Stockholder Agreement; Employment Agreements and
Confidentiality Agreement' of the Offer to Purchase dated June 2, 1999 (the
'Offer to Purchase'). The Purchaser's right to purchase the Shares subject to
the Stockholder Agreement is reflected in Row 11 of each of the tables above.
The Stockholder Agreement is described more fully in Section 12 'The Merger
Agreement; Stockholder Agreement; Employment Agreements and Confidentiality
Agreement' of the Offer to Purchase.

     In addition, pursuant to the Merger Agreement, the Company has granted the
Purchaser an irrevocable option (the 'Purchaser Stock Option') to purchase up to
690,172 Shares, which represents approximately 19.9% of the Company's
outstanding Common Stock, at a price per share equal to the Offer price payable
in cash. The Purchaser Stock Option may be exercised, in whole or in part, at
any time and from time to time after the date on which the Purchaser has
accepted for payment the Shares tendered pursuant to the Offer and subject to
satisfaction of the Minimum Condition if, but only if, Parent and Purchaser
agree to permanently waive the offer conditions set forth in the Merger
Agreement. The Purchaser Stock Option is reflected in Row 11 of each of the
tables above.

     This Tender Offer Statement on Schedule 14D-1 also constitutes a Statement
on Schedule 13D with respect to the acquisition by the Purchaser, Parent and
Perstorp AB of beneficial ownership of the Shares subject to the Stockholder
Agreement and the Purchaser Stock Option. The item numbers and responses thereto
below are in accordance with the requirements of Schedule 14D-1.

ITEM 1. SECURITY AND SUBJECT COMPANY.

     (a) The name of the subject company is Endogen, Inc., a Massachusetts
corporation (the 'Company'), which has its principal executive offices at 30
Commerce Way, Woburn, Massachusetts 01801.

     (b) This Schedule 14D-1 relates to the offer by the Purchaser to purchase
all outstanding Shares (as defined in the Offer) at a price of $3.75 per Share,
net to the seller in cash, without interest thereon (the 'Offer Price'), upon
the terms and subject to the conditions set forth in the Offer to Purchase and
in the related Letter of Transmittal (which, together with any amendments or
supplements thereto, collectively constitute the 'Offer'), copies of which are
attached hereto as Exhibits (a)(1) and (a)(2), respectively. Information
concerning the number of outstanding Shares is set forth in the 'Introduction'
of the Offer to Purchase and is incorporated herein by reference.

     (c) Information concerning the principal market in which the Shares trade
and the trading prices thereof for each quarterly period during the past two
years during which the Shares were publicly traded, is set forth in Section 6
'Price Range of Shares; Dividends' of the Offer to Purchase and is incorporated
herein by reference.

                                       5

<PAGE>
ITEM 2. IDENTITY AND BACKGROUND.

     (a)-(d) and (g) This Schedule 14D-1 is being filed by the Purchaser, a
Massachusetts corporation, Parent, a Swedish corporation and Perstorp AB, a
Swedish corporation ('Perstorp'). The Purchaser is a wholly owned subsidiary of
Parent, which is a wholly owned subsidiary of Perstorp. Information concerning
the principal business and the address of the principal offices of the
Purchaser, Parent and Perstorp is set forth in Section 9 'Certain Information
Concerning Perstorp, the Purchaser and Parent' of the Offer to Purchase and is
incorporated herein by reference. The names, business addresses, present
principal occupations or employment, material occupations, positions, offices or
employments during the last five years and citizenship of the directors and
executive officers of the Purchaser, Parent and Perstorp are set forth in
Schedule I to the Offer to Purchase and are incorporated herein by reference.

     (e) and (f) The information set forth in Section 9 'Certain Information
Concerning Perstorp, the Purchaser and Parent' of the Offer to Purchase is
incorporated herein by reference. Neither Parent, the Purchaser, Perstorp nor,
to the best of their knowledge, any of the persons listed on Schedule I, was a
party to a civil proceeding of a judicial or administrative body of competent
jurisdiction and as a result of such proceeding was or is subject to a judgment,
decree or final order enjoining future violations of, or prohibiting activities
subject to, Federal or State securities laws or finding any violation of such
laws.

ITEM 3. PAST CONTACTS, TRANSACTIONS OR NEGOTIATIONS WITH THE SUBJECT COMPANY.

     (a) and (b) The information set forth in Section 10 'Background of the
Offer; Contacts with the Company' and Section 11 'Purpose of the Offer and the
Merger; Plans for the Company; Appraisal Rights' of the Offer to Purchase is
incorporated herein by reference.

ITEM 4. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

     (a) and (b) The information set forth in Section 13 'Source and Amount of
Funds' of the Offer to Purchase is incorporated herein by reference.

     (c) Not applicable.

ITEM 5. PURPOSE OF THE TENDER OFFER AND PLAN OR PROPOSALS OF THE BIDDER.

     (a)-(e) The information set forth in Section 11 'Purpose of the Offer and
the Merger; Plans for the Company; Appraisal Rights' of the Offer to Purchase is
incorporated herein by reference.

     (f) and (g) The information set forth in Section 7 'Effect of the Offer on
the Market for the Shares; Nasdaq and Boston Stock Exchange Quotations; Exchange
Act Registration; Margin Regulations' of the Offer to Purchase is incorporated
herein by reference.

ITEM 6. INTEREST IN SECURITIES OF THE SUBJECT COMPANY.

     (a) and (b) The information set forth in 'Introduction,' Section 9 'Certain
Information Concerning Perstorp, the Purchaser and Parent,' Section 11 'Purpose
of the Offer and the Merger; Plans for the Company; Appraisal Rights'; and
Section 12 'The Merger Agreement; Stockholder Agreement; Employment Agreements
and Confidentiality Agreement' of the Offer to Purchase is incorporated herein
by reference.

ITEM 7. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO
THE SUBJECT COMPANY'S SECURITIES.

     The information set forth in 'Introduction,' Section 9 'Certain Information
Concerning Perstorp, the Purchaser and Parent,' Section 10 'Background of the
Offer; Contacts with the Company,' Section 11 'Purpose of the Offer and the
Merger; Plans for the Company; Appraisal Rights,' Section 12 'The Merger
Agreement; Stockholder Agreement; Employment Agreements and Confidentiality
Agreement,' and Section 13 'Source and Amount of Funds' of the Offer to Purchase
is incorporated herein by reference.

ITEM 8. PERSONS RETAINED, EMPLOYED OR TO BE COMPENSATED.

     The information set forth in 'Introduction' and in Section 16 'Fees and
Expenses' of the Offer to Purchase is incorporated herein by reference.

                                       6

<PAGE>
ITEM 9. FINANCIAL STATEMENTS OF CERTAIN BIDDERS.

     The information set forth in Section 9 'Certain Information Concerning
Perstorp, the Purchaser and Parent' of the Offer to Purchase is incorporated
herein by reference.

ITEM 10. ADDITIONAL INFORMATION.

     (a) The information set forth in Section 11 'Purpose of the Offer and the
Merger; Plans for the Company; Appraisal Rights' and Section 12 'The Merger
Agreement; Stockholder Agreement; Employment Agreements; and Confidentiality
Agreement' of the Offer to Purchase is incorporated herein by reference.

     (b) and (c) The information set forth in Section 15 'Certain Legal Matters'
of the Offer to Purchase is incorporated herein by reference.

     (d) The information set forth in Section 7 'Effect of the Offer on the
Market for the Shares; Nasdaq and Boston Stock Exchange Quotations; Exchange Act
Registration; Margin Regulations' and Section 13 'Source and Amount of Funds' is
incorporated herein by reference.

     (e) None.

     (f) The information set forth in the Offer to Purchase, the Letter of
Transmittal, the Agreement and Plan of Merger dated as of May 27, 1999 and
related Letter Agreement, among the Purchaser, Parent and the Company, the
Stockholder Agreement the Employment Agreements, copies of which are attached
hereto as Exhibits (a)(1), (a)(2), (c)(1), (c)(2), (c)(3) and (c)(4),
respectively, is incorporated herein by reference.

ITEM 11. MATERIAL TO BE FILED AS EXHIBITS.

<TABLE>
<CAPTION>
<S>      <C>
(a)(1)   -- Offer to Purchase.
(a)(2)   -- Letter of Transmittal.
(a)(3)   -- Notice of Guaranteed Delivery.
(a)(4)   -- Letter to Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees.
(a)(5)   -- Letter to Clients for use by Brokers, Dealers, Banks, Trust Companies and Other Nominees.
(a)(6)   -- Guidelines of the Internal Revenue Service for Certification of Taxpayer Identification Number on
            Substitute Form W-9.
(a)(7)   -- Form of Summary Advertisement.
(a)(8)   -- Text of U.S. Press Release dated May 27, 1999.
(a)(9)   -- Text of Swedish Press Release dated May 27, 1999.
(c)(1)   -- Agreement and Plan of Merger dated as of May 27, 1999 and related Letter Agreement, among the Purchaser,
            Parent and the Company. (Schedules to the Agreement and Plan of Merger are omitted in accordance with
            applicable regulations of the Commission. Copies of such Schedules will be provided to the Commission
            upon request.)
(c)(2)   -- Stockholder Agreement dated as of May 27, 1999, among Parent, the Purchaser, Owen A. Dempsey, Hayden H.
            Harris, Charles R. Burke, Christine A. Burns, Avery W. Catlin, Wallace G. Dempsey, Irwin J. Gruverman,
            G&G Diagnostics Limited Partnership I, Hayden H. Harris Living Trust DTD 3/6/98 and Wolfgang Woloszczuk.
(c)(3)   -- Employment Agreement executed May 27, 1999 between the Purchaser and Owen A. Dempsey.
(c)(4)   -- Employment Agreement executed May 27, 1999, between the Purchaser and Christine A. Burns.
(d)      -- None.
(e)      -- Not applicable.
(f)      -- None.
</TABLE>

                                       7

<PAGE>
                                   SIGNATURES

     After due inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.

Dated: June 2, 1999

                                       EWOK ACQUISITION CORP.

                                       By: /s/ ROBB ANDERSON
                                            ....................................
                                           NAME: ROBB ANDERSON
                                           TITLE: PRESIDENT

                                       PERBIO SCIENCE AB

                                       By: /s/ MATS FISCHIER
                                            ....................................
                                           NAME: MATS FISCHIER
                                           TITLE: DIRECTOR

                                       PERSTORP AB
                                       By: /s/ AKE FREDRIKSSON
                                            ....................................
                                           NAME: AKE FREDRIKSSON
                                           TITLE: PRESIDENT AND CHIEF EXECUTIVE
                                           OFFICER

                                       8

<PAGE>
                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
    EXHIBIT
     NUMBER                                             DESCRIPTION                                              PAGE
    --------  ------------------------------------------------------------------------------------------------   -----
    <S>        <C>                                                                                              <C>
     (a)(1)  -- Offer to Purchase............................................................................
     (a)(2)  -- Letter of Transmittal........................................................................
     (a)(3)  -- Notice of Guaranteed Delivery................................................................
     (a)(4)  -- Letter to Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees.............
     (a)(5)  -- Letter to Clients for use by Brokers, Dealers, Banks, Trust Companies and Other Nominees.....
     (a)(6)  -- Guidelines of the Internal Revenue Service for Certification of Taxpayer Identification
                Number on Substitute Form W-9................................................................
     (a)(7)  -- Form of Summary Advertisement................................................................
     (a)(8)  -- Text of U.S. Press Release dated May 27, 1999................................................
     (a)(9)  -- Text of Swedish Press Release dated May 27, 1999.............................................
     (c)(1)  -- Agreement and Plan of Merger and related Letter Agreement dated as of May 27, 1999, among the
                Purchaser, Parent and the Company (Schedules to the Agreement and Plan of Merger are omitted
                in accordance with applicable regulations of the Commission. Copies of such Schedules will be
                provided to the Commission upon request.)....................................................
     (c)(2)  -- Stockholder Agreement dated as of May 27, 1999, among Parent, the Purchaser, Owen A. Dempsey,
                Hayden H. Harris, Charles R. Burke, Christine A. Burns, Avery W. Catlin, Wallace G. Dempsey,
                Irwin J. Gruverman, G&G Diagnostics Limited Partnership I, Hayden H. Harris Living Trust DTD
                3/6/98 and Wolfgang Woloszczuk...............................................................
     (c)(3)  -- Employment Agreement executed May 27, 1999 between the Purchaser and Owen A. Dempsey.........
     (c)(4)  -- Employment Agreement executed May 27, 1999, between the Purchaser and Christine A. Burns.....
</TABLE>









<PAGE>

                               OFFER TO PURCHASE
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                                 ENDOGEN, INC.
                                       AT
                          $3.75 NET PER SHARE IN CASH
                                       BY
                             EWOK ACQUISITION CORP.
                           A WHOLLY OWNED SUBSIDIARY
                                       OF
                               PERBIO SCIENCE AB

 THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
        TIME, ON TUESDAY, JUNE 29, 1999, UNLESS THE OFFER IS EXTENDED.


THE BOARD OF DIRECTORS OF ENDOGEN, INC. HAS APPROVED THE AGREEMENT AND PLAN OF
MERGER DATED AS OF MAY 27, 1999 (THE 'MERGER AGREEMENT') AND HAS DETERMINED THAT
THE OFFER AND THE MERGER ARE FAIR TO AND IN THE BEST INTERESTS OF THE
STOCKHOLDERS OF ENDOGEN, INC. AND RECOMMENDS THAT ALL OF THE STOCKHOLDERS OF
ENDOGEN, INC. ACCEPT THE OFFER, TENDER THEIR SHARES AND APPROVE THE MERGER
AGREEMENT AND THE MERGER, IF REQUIRED BY LAW.

THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY TENDERED
AND NOT WITHDRAWN ON OR PRIOR TO THE EXPIRATION DATE (AS DEFINED BELOW) THAT
NUMBER OF OUTSTANDING SHARES WHICH, TOGETHER WITH THE OUTSTANDING SHARES SUBJECT
TO THE STOCKHOLDER AGREEMENT THAT SHALL NOT HAVE BEEN SO TENDERED, WOULD
REPRESENT AT LEAST TWO-THIRDS OF ALL OUTSTANDING SHARES ON A FULLY DILUTED BASIS
(AS DEFINED BELOW). SEE SECTION 14. THE OFFER IS NOT CONDITIONED ON OBTAINING
FINANCING.

                                   IMPORTANT

     Any stockholder desiring to tender all or any portion of such stockholder's
Shares should either (1) complete and sign the Letter of Transmittal or a
facsimile copy thereof in accordance with the instructions in the Letter of
Transmittal, mail or deliver it and any other required documents to the
Depositary and either mail or deliver certificates evidencing or representing
such Shares to the Depositary (with the Letter of Transmittal and any other
required documents) or tender such Shares pursuant to the procedure for book
entry transfer set forth in Section 2 or (2) request such stockholder's broker,
dealer, commercial bank, trust company or other nominee to effect the
transaction for such stockholder. A stockholder having Shares registered in the
name of a broker, dealer, commercial bank, trust company or other nominee must
contact such stockholder's broker, dealer, commercial bank, trust company or
other nominee if such stockholder desires to tender such Shares.

     Any stockholder who desires to tender such stockholder's Shares and whose
certificates evidencing or representing such Shares are not immediately
available, or who cannot comply with the procedures for book-entry transfer on a
timely basis, may tender such Shares by following the procedures for guaranteed
delivery set forth in Section 2.

     Questions and requests for assistance may be directed to the Information
Agent or the Dealer Manager at their respective addresses and telephone numbers
set forth on the back cover of this Offer to Purchase. Requests for additional
copies of this Offer to Purchase, the Letter of Transmittal, the Notice of
Guaranteed Delivery or other related materials may be directed to the
Information Agent or to brokers, dealers, commercial banks or trust companies.

                      The Dealer Manager for the Offer is:
                     Vector Securities International, Inc.
                                  June 2, 1999





<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                                PAGE
                                                                                                                ----

<S>                                                                                                             <C>
                                                                                                                  3
Introduction.................................................................................................

  1.  Terms of the Offer.....................................................................................     4

  2.  Procedures for Tendering Shares........................................................................     6

  3.  Withdrawal Rights......................................................................................     9

  4.  Acceptance for Payment and Payment of Purchase Price...................................................     9

  5.  Certain Federal Income Tax Considerations..............................................................    10

  6.  Price Range of Shares; Dividends.......................................................................    11

  7.  Effect of the Offer on the Market for the Shares; Nasdaq and Boston Stock Exchange Quotations; Exchange
      Act Registration; Margin Regulations...................................................................    11

  8.  Certain Information Concerning the Company.............................................................    13

  9.  Certain Information Concerning Perstorp, the Purchaser and Parent......................................    14

 10.  Background of the Offer; Contacts with the Company.....................................................    15

 11.  Purpose of the Offer and the Merger; Plans for the Company; Appraisal Rights...........................    16

 12.  The Merger Agreement; Stockholder Agreement; Employment Agreements And Confidentiality Agreement.......    17

 13.  Source and Amount of Funds.............................................................................    24

 14.  Certain Conditions of the Offer........................................................................    25

 15.  Certain Legal Matters..................................................................................    26

 16.  Fees and Expenses......................................................................................    28

 17.  Miscellaneous..........................................................................................    28

                                                                                                                S-1
Schedule I...................................................................................................
</TABLE>

                                       2





<PAGE>

TO ALL HOLDERS OF SHARES OF COMMON STOCK OF ENDOGEN, INC.:

                                  INTRODUCTION

     EWOK Acquisition Corp., a Massachusetts corporation (the 'Purchaser') and a
wholly owned subsidiary of PerBio Science AB, a Swedish corporation ('Parent'),
hereby offers to purchase all outstanding shares of the Common Stock (the
'Common Stock'), $.01 par value (the 'Shares'), of Endogen, Inc., a
Massachusetts corporation (the 'Company'), at a purchase price of $3.75 per
Share, net to the seller in cash, without interest thereon (the 'Offer Price'),
upon the terms and subject to the conditions set forth in this Offer to Purchase
and the related Letter of Transmittal (which, together with any amendments or
supplements thereto, collectively constitute the 'Offer').

     Tendering stockholders will not be obligated to pay brokerage fees or
commissions or, except as set forth in Instruction 6 of the Letter of
Transmittal, transfer taxes on the purchase of Shares pursuant to the Offer. The
Purchaser will pay all charges and expenses of Vector Securities International,
Inc. (the 'Dealer Manager'), American Stock Transfer & Trust Company (the
'Depositary') and Georgeson & Company, Inc. (the 'Information Agent').

     Parent and the Purchaser are corporations affiliated with Perstorp AB, a
Swedish corporation ('Perstorp'). All of the outstanding shares of the capital
stock of the Purchaser are owned by Parent and all of the outstanding shares of
the capital stock of Parent are owned by Perstorp. For more information
concerning Perstorp, Parent and the Purchaser, see Section 9.

     THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN ON OR PRIOR TO THE EXPIRATION DATE (AS DEFINED IN
SECTION 1) THAT NUMBER OF OUTSTANDING SHARES WHICH, TOGETHER WITH THE
OUTSTANDING SHARES SUBJECT TO THE STOCKHOLDER AGREEMENT (AS DEFINED BELOW) THAT
SHALL NOT HAVE BEEN SO TENDERED, WOULD REPRESENT AT LEAST TWO-THIRDS OF ALL
OUTSTANDING SHARES ON A FULLY DILUTED BASIS (AS DEFINED BELOW) (THE 'MINIMUM
CONDITION'). THE PURCHASER RESERVES THE RIGHT (SUBJECT TO OBTAINING THE EXPRESS
WRITTEN CONSENT OF THE COMPANY AND COMPLIANCE WITH THE APPLICABLE RULES AND
REGULATIONS OF THE SECURITIES AND EXCHANGE COMMISSION (THE 'COMMISSION')), WHICH
IT PRESENTLY HAS NO INTENTION OF EXERCISING, TO WAIVE OR REDUCE THE MINIMUM
CONDITION. SEE SECTIONS 1 AND 14.

     THE OFFER IS NOT CONDITIONED ON OBTAINING FINANCING.

     THE BOARD OF DIRECTORS OF THE COMPANY (THE 'BOARD') HAS APPROVED THE MERGER
AGREEMENT (AS DEFINED BELOW) AND HAS DETERMINED THAT THE OFFER AND THE MERGER
(AS DEFINED BELOW) ARE FAIR TO AND IN THE BEST INTERESTS OF THE STOCKHOLDERS OF
THE COMPANY AND RECOMMENDS THAT ALL OF THE STOCKHOLDERS OF THE COMPANY ACCEPT
THE OFFER, TENDER THEIR SHARES AND APPROVE THE MERGER AGREEMENT AND THE MERGER,
IF REQUIRED BY LAW. ADAMS, HARKNESS & HILL, INC. ('AH&H'), THE COMPANY'S
FINANCIAL ADVISOR, HAS DELIVERED TO THE BOARD A WRITTEN OPINION DATED MAY 27,
1999, TO THE EFFECT THAT, AS OF SUCH DATE AND BASED UPON AND SUBJECT TO CERTAIN
MATTERS STATED IN SUCH OPINION, THE $3.75 PER SHARE CASH CONSIDERATION TO BE
RECEIVED BY HOLDERS OF SHARES (OTHER THAN PARENT AND ITS AFFILIATES) PURSUANT TO
THE OFFER AND THE MERGER WAS FAIR, FROM A FINANCIAL POINT OF VIEW, TO SUCH
HOLDERS. A COPY OF THE OPINION OF AH&H IS INCLUDED AS AN ANNEX TO THE COMPANY'S
SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9, WHICH IS BEING MAILED
TO STOCKHOLDERS HEREWITH, AND SHOULD BE READ CAREFULLY IN ITS ENTIRETY.

     The Offer is being made pursuant to an Agreement and Plan of Merger dated
as of May 27, 1999 (the 'Merger Agreement'), among Parent, the Purchaser and the
Company. The Merger Agreement provides that the Purchaser will be merged (the
'Merger') with and into the Company after the completion of the Offer and the
satisfaction of certain conditions. As a result of the Merger, each Share issued
and outstanding immediately prior to the Effective Time (as defined in the
Merger Agreement) (other than Shares then owned by the Company, Parent, any
direct or indirect subsidiary of Parent or by stockholders of the Company, if
any, who dissent from the Merger and comply with all of the provisions of the
Massachusetts Business Corporation Law (the 'MBCL') concerning the right, if
applicable, of holders of Shares to seek appraisal of their Shares) will be
converted into the right to receive the price paid in the Offer in cash, without
interest (the 'Merger Consideration'). See Section 12 'The Merger Agreement.'

                                       3





<PAGE>

     The consummation of the Merger is subject to the satisfaction or waiver of
a number of conditions, including, if required by law, the approval and adoption
of the Merger Agreement by the stockholders of the Company. If the Minimum
Condition is satisfied, the Purchaser will have sufficient voting power under
the MBCL to effect the Merger without the concurrence of any other stockholder
of the Company. If at least 90% of the outstanding Shares are purchased in the
Offer, the Purchaser will be able to effect a short-form merger under the MBCL
without a vote of stockholders.

     In connection with the execution of the Merger Agreement, the Purchaser and
Parent entered into a Stockholder Agreement, dated as of May 27, 1999 (the
'Stockholder Agreement'), with Owen A. Dempsey, the President and Chief
Executive Officer of the Company, Hayden H. Harris, Chairman of the Board,
Charles R. Burke, Christine A. Burns, Avery W. Catlin, Wallace G. Dempsey, Irwin
J. Gruverman, G&G Diagnostics Limited Partnership I, Hayden H. Harris Living
Trust DTD 3/6/98 and Wolfgang Woloszczuk (collectively, the 'Selling
Stockholders'), pursuant to which such Selling Stockholders have agreed to
tender pursuant to the Offer, all Shares beneficially owned by them, including
569,600 Shares currently outstanding which represent approximately 16% of the
Shares issued and outstanding, plus Shares subsequently acquired by a Selling
Stockholder through the exercise of options or otherwise, at a price per Share
equal to the price paid in the Offer, provided that such obligation to tender is
subject to certain conditions, including the Minimum Condition having been
satisfied and the Purchaser having accepted Shares for payment under the Offer.
Pursuant to the Stockholder Agreement, each Selling Stockholder has also
executed and delivered a proxy for the benefit of the Purchaser with respect to
the Shares subject to the Stockholder Agreement owned by such Selling
Stockholder to vote such Shares against certain competing transactions, as more
fully described below in Section 12 'The Stockholder Agreement.'

     Pursuant to the Merger Agreement, the Company has granted the Purchaser an
irrevocable option (the 'Purchaser Stock Option') to purchase up to 690,172
Shares, which represents approximately 19.9% of the Company's outstanding Common
Stock (the 'Option Shares') at a price per share equal to the Offer Price
payable in cash. The Purchaser Stock Option may be exercised, in whole or in
part, at any time and from time to time after the date on which the Purchaser
has accepted for payment the Shares tendered pursuant to the Offer and subject
to satisfaction of the Minimum Condition if, but only if, Parent and Purchaser
agree to permanently waive the Offer Conditions set forth in the Merger
Agreement. See Section 12 'The Merger Agreement.'

     The Company has represented to Parent and the Purchaser that, as of May 26,
1999, there were 3,468,202 Shares issued and outstanding, and 1,249,450 Shares
reserved for issuance upon the exercise of outstanding options and warrants.

     STOCKHOLDERS ARE URGED TO READ THIS OFFER TO PURCHASE AND THE RELATED
LETTER OF TRANSMITTAL CAREFULLY BEFORE DECIDING WHETHER TO TENDER THEIR SHARES
PURSUANT TO THE OFFER.

1. TERMS OF THE OFFER

     Upon the terms and subject to the conditions set forth in the Offer
(including, if the Offer is extended or amended, the terms and conditions of any
extension or amendment), the Purchaser will accept for payment (and thereby
purchase) all Shares that are validly tendered on or prior to the Expiration
Date and not properly withdrawn as permitted by Section 3. The term 'Expiration
Date' means 12:00 Midnight, New York City time, on Tuesday, June 29, 1999,
unless and until the Purchaser, in its sole discretion, shall have extended the
period of time for which the Offer is open, in which event the term 'Expiration
Date' shall mean the latest time and date at which the Offer, as so extended by
the Purchaser, shall expire.

     If the conditions of the Offer are not satisfied or waived prior to the
Expiration Date, the Purchaser reserves the right (but shall not be obligated),
subject to the terms and conditions contained in the Merger Agreement and to the
applicable rules and regulations of the Commission, (1) to terminate the Offer
and not accept for payment any Shares and return all tendered Shares to
tendering stockholders, (2) to waive all the unsatisfied conditions (other than
the Minimum Condition) and, subject to complying with the terms of the Merger
Agreement and the applicable rules and regulations of the Commission, to waive
the Minimum Condition, to accept for payment and pay for all Shares

                                       4





<PAGE>

validly tendered prior to the Expiration Date and not theretofore withdrawn,
(3) to extend the Offer and, subject to the right of stockholders to withdraw
Shares until the Expiration Date, to retain the Shares that have been tendered
for the period or periods for which the Offer is extended or (4) to amend the
Offer.

     There can be no assurance that the Purchaser will exercise its right to
extend the Offer (other than as required by the Merger Agreement or applicable
law). Any extension, amendment or termination of the Offer, or any waiver of any
condition of the Offer, will be followed as promptly as practicable by a public
announcement. In the case of an extension, Rule 14e-1(d) under the Securities
Exchange Act of 1934, as amended (the 'Exchange Act'), requires that the
announcement be issued no later than 9:00 a.m., New York City time, on the next
business day after the previously scheduled Expiration Date in accordance with
the public announcement requirements of Rule 14d-4(c) under the Exchange Act.
Subject to applicable law (including Rules 14d-4(c) and 14d-6(d) under the
Exchange Act, which require that any material change in the information
published, sent or given to stockholders in connection with the Offer be
promptly disseminated to stockholders in a manner reasonably designed to inform
stockholders of such change), and without limiting the manner in which the
Purchaser may choose to make any public announcement, the Purchaser will not
have any obligation to publish, advertise or otherwise communicate any such
public announcement other than by making a release to the Dow Jones News
Service. During any such extension, all Shares previously tendered and not
withdrawn will remain subject to the Offer and the right of a tendering
stockholder to withdraw such stockholder's Shares in accordance with the
procedures set forth in Section 3.

     In the Merger Agreement, the Purchaser has agreed that it will not, without
the prior consent of the Company, extend the Offer, except that, without the
consent of the Company, the Purchaser may extend the Offer (1) if at the
Expiration Date any of the conditions to the Purchaser's obligation to accept
Shares for payment are not satisfied or waived, until such time as such
conditions are satisfied or waived (provided, each individual extension will not
exceed five (5) business days after the previously scheduled Expiration Date),
(2) for any period required by any rule, regulation, interpretation or position
of the Commission or the staff thereof and (3) on up to two occasions in each
case for a period of not more than five (5) business days beyond the latest
Expiration Date if on such Expiration Date there shall have been tendered more
than the number of Shares sufficient to satisfy the Minimum Condition but less
than 90% of the Shares. As used in this Offer to Purchase, 'business day' has
the meaning set forth in Rule 14d-1 under the Exchange Act. THE PURCHASER SHALL
NOT HAVE ANY OBLIGATION TO PAY INTEREST ON THE PURCHASE PRICE FOR TENDERED
SHARES, WHETHER OR NOT THE PURCHASER EXERCISES ITS RIGHT TO EXTEND THE OFFER.

     In addition, the Purchaser has agreed in the Merger Agreement that it will
not, without the consent of the Company, (1) reduce the number of Shares subject
to the Offer, (2) reduce the Offer Price, (3) add to or modify the conditions
set forth in Section 14, including the Minimum Condition, (4) except as provided
in the previous paragraph, extend the Offer, (5) change the form of the
consideration payable in the Offer or (6) amend or alter any term of the Offer
in a manner materially adverse to the Company's stockholders; provided, however,
that nothing contained in the Merger Agreement will prohibit the Purchaser, in
its sole discretion without the consent of the Company, from waiving
satisfaction of any condition of the Offer other than the Minimum Condition.

     If the Purchaser extends the Offer or if the Purchaser (whether before or
after its acceptance for payment of Shares) is delayed in its acceptance for
payment of or payment for Shares or it is unable to pay for Shares pursuant to
the Offer for any reason, then, without prejudice to the Purchaser's rights
under the Offer, the Depositary may retain tendered Shares on behalf of the
Purchaser, and such Shares may not be withdrawn except to the extent tendering
stockholders are entitled to withdrawal rights as described in Section 3.
However, the ability of the Purchaser to delay the payment for Shares that the
Purchaser has accepted for payment is limited by Rule 14e-1 under the Exchange
Act, which requires that a bidder pay the consideration offered or return the
securities deposited by or on behalf of holders of securities promptly after the
termination or withdrawal of such bidder's offer.

     If the Purchaser makes a material change in the terms of the Offer or the
information concerning the Offer or waives a material condition of the Offer
(including, with the Company's consent, the Minimum Condition), the Purchaser
will disseminate additional tender offer materials and extend the

                                       5





<PAGE>

Offer to the extent required by Rules 14d-4(c), 14d-6(d) and 14e-1 under the
Exchange Act. The minimum period during which an offer must remain open
following material changes in the terms of the Offer or information concerning
the Offer, other than a change in price or a change in the percentage of
securities sought or any dealer solicitation fee, will depend upon the facts and
circumstances then existing, including the relative materiality of the changed
terms or information. With respect to a change in price or a change in the
percentage of securities sought, a minimum period of ten business days is
generally required to allow for adequate dissemination to stockholders.

     Consummation of the Offer is conditioned upon satisfaction of the Minimum
Condition and the other conditions set forth in Section 14. For purposes of
determining the Minimum Condition, the term 'fully diluted basis' excludes the
following: (a) all outstanding stock options issued pursuant to the Company's
1992 Stock Plan that are irrevocably terminated, consistent with Section
7.4(a)(A)(i) or (B) of the Merger Agreement, effective as of the time that the
Purchaser accepts for payment, and pays for, all Shares tendered and not
withdrawn pursuant to the Offer; (b) all outstanding options issued pursuant to
the Company's 1993 Non-Employee Director Stock Option Plan that are irrevocably
terminated by the holders of those options, effective as of the time that the
Purchaser accepts for payment, and pays for, all Shares tendered, and not
withdrawn pursuant to the Offer; and (c) a certain warrant to purchase 125,000
shares of Common Stock held by Third Wave Technologies, Inc.; provided that such
warrant is irrevocably terminated by the holder thereof, effective as of the
time that the Purchaser accepts for payment, and pays for, all Shares tendered
and not withdrawn pursuant to the Offer. Subject to the terms and conditions
contained in the Merger Agreement, the Purchaser reserves the right (but shall
not be obligated) to waive any or all of such conditions.

     The Company has provided the Purchaser with the Company's stockholder lists
and security position listings for the purpose of disseminating the Offer to
holders of the Shares. This Offer to Purchase, the related Letter of Transmittal
and other relevant materials will be mailed by the Purchaser to record holders
of Shares and will be furnished by the Purchaser to brokers, dealers, banks,
trust companies and similar persons whose names, or the names of whose nominees,
appear on the stockholder lists or, if applicable, who are listed as
participants in a clearing agency's security position listing, for subsequent
transmittal to beneficial owners of Shares.

2. PROCEDURES FOR TENDERING SHARES

     Valid Tender. For a stockholder to validly tender Shares pursuant to the
Offer, either (1) a properly completed and duly executed Letter of Transmittal
(or facsimile thereof), together with any required signature guarantees (or an
Agent's Message (as hereinafter defined) in connection with a book-entry
transfer of Shares) and any other documents required by the Letter of
Transmittal, must be received by the Depositary at one of its addresses set
forth on the back cover page of this Offer to Purchase and either certificates
for tendered Shares must be received by the Depositary at one of such addresses
or such Shares must be delivered pursuant to the procedure for book entry
transfer set forth below (and a Book-Entry Confirmation (as hereinafter defined)
received by the Depositary), in each case, on or prior to the Expiration Date,
or (2) the tendering stockholder must comply with the guaranteed delivery
procedure set forth below.

     The Depositary will establish an account with respect to the Shares at The
Depository Trust Company (the 'Book-Entry Transfer Facility') for purposes of
the Offer within two business days after the date of this Offer to Purchase. Any
financial institution that is a participant in any of the Book-Entry Transfer
Facility's systems may make book-entry delivery of Shares by causing the Book
Entry Transfer Facility to transfer such Shares into the Depositary's account in
accordance with such Book-Entry Transfer Facility's procedures for such
transfer. However, although delivery of Shares may be effected through book
entry transfer into the Depositary's account at the Book-Entry Transfer
Facility, the Letter of Transmittal (or facsimile thereof), properly completed
and duly executed, with any required signature guarantees (or an Agent's Message
in connection with a book-entry transfer) and any other required documents,
must, in any case, be transmitted to, and received by the Depositary, at one of
its addresses set forth on the back cover of this Offer to Purchase prior to the
Expiration Date, or the tendering stockholder must comply with the guaranteed
delivery procedure described below. The confirmation of a book-entry transfer of
Shares into the Depositary's account at the Book-Entry

                                       6





<PAGE>

Transfer Facility as described above is referred to herein as a 'Book-Entry
Confirmation.' DELIVERY OF DOCUMENTS TO THE BOOK-ENTRY TRANSFER FACILITY IN
ACCORDANCE WITH SUCH BOOK-ENTRY TRANSFER FACILITY'S PROCEDURES DOES NOT
CONSTITUTE DELIVERY TO THE DEPOSITARY.

     The term 'Agent's Message' means a message, transmitted by the Book-Entry
Transfer Facility to, and received by, the Depositary and forming a part of a
Book-Entry Confirmation, which states that such Book-Entry Transfer Facility has
received an express acknowledgment from the participant in such Book-Entry
Transfer Facility tendering the Shares which are the subject of such Book Entry
Confirmation that such participant has received and agrees to be bound by the
terms of the Letter of Transmittal, and that the Purchaser may enforce such
agreement against such participant.

     THE METHOD OF DELIVERY OF SHARES, THE LETTER OF TRANSMITTAL AND ALL OTHER
REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH THE BOOK-ENTRY TRANSFER FACILITY,
IS AT THE ELECTION AND RISK OF THE TENDERING STOCKHOLDER. SHARES WILL BE DEEMED
DELIVERED ONLY WHEN ACTUALLY RECEIVED BY THE DEPOSITARY. IF DELIVERY IS BY MAIL,
REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS RECOMMENDED.
IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.
DELIVERY OF THE LETTER OF TRANSMITTAL AND ACCOMPANYING SHARES WILL BE DEEMED
EFFECTIVE, AND RISK OF LOSS WITH RESPECT TO SUCH LETTER OF TRANSMITTAL AND
ACCOMPANYING CERTIFICATE(S) WILL PASS, ONLY WHEN SUCH LETTER OF TRANSMITTAL AND
ACCOMPANYING CERTIFICATE(S) ARE OFFICIALLY RECEIVED BY THE DEPOSITARY.

     Signature Guarantees. No signature guarantee is required on the Letter of
Transmittal if (1) the Letter of Transmittal is signed by the registered holder
of Shares (which term, for purposes of this Section, includes any participant in
any of the Book-Entry Transfer Facility's systems whose name appears on a
security position listing as the owner of the Shares) tendered therewith and
such registered holder has not completed either the box entitled 'Special
Delivery Instructions' or the box entitled 'Special Payment Instructions' on the
Letter of Transmittal or (2) such Shares are tendered for the account of a firm
that is a participant in the Securities Transfer Agents Medallion Program or the
New York Stock Exchange Medallion Signature Guarantee Program or the Stock
Exchange Medallion Program or by any other 'eligible guarantor institution,' as
such term is defined in Rule 17Ad-15 under the Exchange Act (each, an 'Eligible
Institution'). In all other cases, all signatures on the Letter of Transmittal
must be guaranteed by an Eligible Institution. See Instructions 1 and 5 to the
Letter of Transmittal. If the certificates for Shares are registered in the name
of a person other than the signer of the Letter of Transmittal, or if payment is
to be made or certificates for Shares not tendered or not accepted for payment
are to be issued to a person other than the registered holder of the
certificates surrendered, the tendered certificates must be endorsed or
accompanied by appropriate stock powers, in either case signed exactly as the
name or names of the registered holders or owners appear on the certificates,
with the signatures on the certificates or stock powers guaranteed as aforesaid.
See Instructions 1 and 5 to the Letter of Transmittal.

     Guaranteed Delivery. If a stockholder desires to tender Shares pursuant to
the Offer and such stockholder's certificates for Shares are not immediately
available or the procedure for book-entry transfer cannot be completed on a
timely basis or time will not permit all required documents to reach the
Depositary prior to the Expiration Date, such stockholder's tender may be
effected if all the following conditions are met:

          (1) such tender is made by or through an Eligible Institution;

          (2) a properly completed and duly executed Notice of Guaranteed
     Delivery, substantially in the form provided by the Purchaser, is received
     by the Depositary, as provided below, on or prior to the Expiration Date;
     and

          (3) the certificates for all tendered Shares, in proper form for
     transfer (or a Book-Entry Confirmation with respect to such Shares),
     together with a properly completed and duly executed Letter of Transmittal
     (or facsimile thereof), with any required signature guarantees and any
     other documents required by the Letter of Transmittal, are received by the
     Depositary within three trading days after the date of execution of such
     Notice of Guaranteed Delivery. A 'trading day' is any day on which the
     Nasdaq Stock Market is open for business.

                                       7





<PAGE>

The Notice of Guaranteed Delivery may be delivered by hand to the Depositary or
transmitted by telegram, facsimile transmission or mail to the Depositary and
must include a guarantee by an Eligible Institution in the form set forth in
such Notice of Guaranteed Delivery.

     Notwithstanding any other provision hereof, payment for Shares accepted for
payment pursuant to the Offer will in all cases be made only after timely
receipt by the Depositary of (1) certificates for Shares (or a Book-Entry
Confirmation with respect to such Shares), (2) a Letter of Transmittal (or
facsimile thereof), properly completed and duly executed, with any required
signature guarantees, or an Agent's Message in connection with a book-entry
transfer of Shares, and (3) any other documents required by the Letter of
Transmittal. Accordingly, tendering stockholders may be paid at different times
depending upon when certificates for Shares or Book-Entry Confirmations are
actually received by the Depositary. UNDER NO CIRCUMSTANCE WILL INTEREST BE PAID
ON THE PURCHASE PRICE OF THE SHARES TO BE PAID BY THE PURCHASER, REGARDLESS OF
ANY EXTENSION OF THE OFFER OR ANY DELAY IN MAKING SUCH PAYMENT.

     The valid tender of Shares pursuant to any of the procedures described
above will constitute a binding agreement between the tendering stockholder and
the Purchaser upon the terms and subject to the conditions of the Offer.

     Appointment as Proxy. By executing a Letter of Transmittal as set forth
above, the tendering stockholder will irrevocably appoint designees of the
Purchaser as such stockholder's attorneys-in-fact and proxies in the manner set
forth in the Letter of Transmittal, each with full power of substitution, to the
full extent of such stockholder's rights with respect to the Shares tendered by
such stockholder and accepted for payment by the Purchaser and with respect to
any and all other Shares or other securities or rights issued or issuable in
respect of such Shares on or after June 2, 1999. All such proxies shall be
considered coupled with an interest in the tendered Shares. Such appointment
will be effective when, and only to the extent that, the Purchaser accepts for
payment Shares tendered by such stockholder as provided herein. Upon such
acceptance for payment, all prior powers of attorney and proxies given by such
stockholder with respect to such Shares or other securities or rights will,
without further action, be revoked and no subsequent powers of attorney and
proxies may be given (and, if given, will not be deemed effective). The
designees of the Purchaser will thereby be empowered to exercise all voting and
other rights with respect to such Shares or other securities or rights in
respect of any annual, special or adjourned meeting of the Company's
stockholders, or otherwise, as they in their sole discretion deem proper. The
Purchaser reserves the right to require that, in order for Shares to be deemed
validly tendered, immediately upon the Purchaser's acceptance for payment of
such Shares, the Purchaser must be able to exercise full voting and other rights
with respect to such Shares and other securities or rights, including voting at
any meeting of stockholders then scheduled. Such powers of attorney and proxies
will be irrevocable and will be granted in consideration of the acceptance for
payment of such Shares in accordance with the terms of the Offer.

     Determination of Validity. All questions as to the validity, form,
eligibility (including time of receipt) and acceptance of any tender of Shares
will be determined by the Purchaser in its sole discretion, which determination
will be final and binding. The Purchaser reserves the absolute right to reject
any or all tenders determined by it not to be in proper form or the acceptance
for payment of or payment for Shares which may, in the opinion of the
Purchaser's counsel, be unlawful. The Purchaser also reserves the absolute right
to waive any defect or irregularity in any tender with respect to any particular
Shares, whether or not similar defects or irregularities are waived in the case
of other Shares. No tender of Shares will be deemed to have been validly made
until all defects or irregularities relating thereto have been cured or waived.
None of the Purchaser, Parent, the Dealer Manager, the Depositary, the
Information Agent or any other person will be under any duty to give
notification of any defects or irregularities in tenders or incur any liability
for failure to give any such notification. The Purchaser's interpretation of the
terms and conditions of the Offer (including the Letter of Transmittal and the
instructions thereto) will be final and binding.

     Backup Withholding. In order to avoid 'backup withholding' of Federal
income tax on payments of cash pursuant to the Offer, a stockholder surrendering
Shares in the Offer must (1) provide the Depositary with such stockholder's
correct taxpayer identification number ('TIN') on a Substitute Form W-9 and (2)
certify under penalty of perjury that such TIN is correct and that such
stockholder is not subject to backup withholding. Certain stockholders
(including, among others, all corporations and

                                       8





<PAGE>

certain foreign individuals and entities) are not subject to backup withholding.
If a stockholder does not provide its correct TIN or fails to provide the
certifications described above, the Internal Revenue Service ('IRS') may impose
a penalty on such stockholder and payment of cash to such stockholder pursuant
to the Offer may be subject to backup withholding of 31%. All stockholders
surrendering Shares pursuant to the Offer should complete and sign the
Substitute Form W-9 included as part of the Letter or Transmittal to provide the
information and certification necessary to avoid backup withholding (unless an
applicable exemption exists and is proved in a manner satisfactory to the
Purchaser and the Depositary). Noncorporate foreign stockholders should complete
and sign a Form W-8, Certificate of Foreign Status, a copy of which may be
obtained from the Depositary, in order to avoid backup withholding. See
Instruction 9 to the Letter of Transmittal.

3. WITHDRAWAL RIGHTS

     Except as otherwise provided in this Section 3, tenders of Shares are
irrevocable. Shares tendered pursuant to the Offer may be withdrawn on or at any
time prior to the Expiration Date and, unless theretofore accepted for payment
and paid for as provided herein, may also be withdrawn on or after August 2,
1999 (or such other date as may apply if the Offer is extended).

     For a withdrawal to be effective, a written, telegraphic or facsimile
transmission notice of withdrawal must be timely received by the Depositary at
one of its addresses set forth on the back cover of this Offer to Purchase and
must specify the name of the person who tendered the Shares to be withdrawn, the
number of Shares to be withdrawn and the name of the registered holder, if
different from that of the person who tendered such Shares. If certificates for
Shares have been delivered or otherwise identified to the Depositary, then,
prior to the physical release of such certificates, the serial numbers shown on
the particular certificates evidencing the Shares to be withdrawn and a signed
notice of withdrawal with signatures guaranteed by an Eligible Institution,
except in the case of Shares tendered by an Eligible Institution, must also be
furnished to the Depositary as aforesaid. If Shares have been delivered pursuant
to the procedure for book-entry transfer set forth in Section 2, any notice of
withdrawal must also specify the name and number of the account at the
Book-Entry Transfer Facility to be credited with the withdrawn Shares and
otherwise comply with the Book-Entry Transfer Facility's procedures.

     Any questions as to the form and validity (including time of receipt) of
notices of withdrawal will be determined by the Purchaser, in its sole
discretion, which determination shall be final and binding on all parties. None
of the Purchaser, Parent, the Dealer Manager, the Depositary, the Information
Agent or any other person will be under any duty to give notification of any
defects or irregularities in any notice of withdrawal or incur any liability for
failure to give any such notification. Any Shares withdrawn will be deemed to be
not validly tendered for purposes of the Offer. However, withdrawn Shares may be
retendered by following one of the procedures described in Section 2 at any time
on or prior to the Expiration Date.

4. ACCEPTANCE FOR PAYMENT AND PAYMENT OF PURCHASE PRICE

     Upon the terms and subject to the conditions of the Offer (including, if
the Offer is extended or amended, the terms and conditions of any such extension
or amendment), the Purchaser will purchase by accepting for payment, and will
pay for, all Shares validly tendered on or prior to the Expiration Date and not
properly withdrawn (in accordance with the procedures set forth in Section 3),
promptly after the Expiration Date. The Purchaser expressly reserves the right
to delay acceptance for payment of, or, subject to Rule 14e-l(c) promulgated
under the Exchange Act, payment for, Shares in order to comply in whole or in
part with any applicable law. See Sections 14 and 15. In all cases, payment for
Shares purchased pursuant to the Offer will be made only after timely receipt by
the Depositary of (1) certificates for such Shares (or a Book-Entry
Confirmation) pursuant to the procedures set forth in Section 2, (2) a Letter of
Transmittal (or a facsimile copy thereof), properly completed and duly executed,
or an 'Agent's Message,' and (3) any other documents required by the Letter of
Transmittal.

     For purposes of the Offer, the Purchaser will be deemed to have accepted
for payment (and thereby purchased) Shares validly tendered to the Purchaser on
or prior to the Expiration Date and not

                                       9





<PAGE>

properly withdrawn if, as and when the Purchaser gives oral or written notice to
the Depositary of the Purchaser's acceptance for payment of such Shares pursuant
to the Offer. Upon the terms and subject to the conditions of the Offer, payment
for Shares purchased pursuant to the Offer will be made by deposit of the
purchase price with the Depositary, which will act as agent for tendering
stockholders for the purpose of receiving payments from the Purchaser and
transmitting payments to tendering stockholders. Under no circumstances will
interest on the purchase price of the Shares be paid by the Purchaser by reason
of any delay in making such payment. If the Purchaser is delayed in its
acceptance for payment or payment for Shares or is unable to accept for payment
or pay for Shares tendered pursuant to the Offer for any reason, then, without
prejudice to the Purchaser's rights under the Offer, the Depositary may, subject
to Rule 14e-1(c) promulgated under the Exchange Act, retain tendered Shares on
behalf of the Purchaser, and such Shares may not be withdrawn except to the
extent tendering stockholders are entitled to withdrawal rights as set forth in
Section 3. The Purchaser will pay any transfer taxes incident to the transfer to
it of validly tendered Shares, except as otherwise provided in Instruction 6 to
the Letter of Transmittal, as well as charges and expenses of the Dealer
Manager, the Depositary and the Information Agent.

     If any tendered Shares are not purchased pursuant to the Offer for any
reason, or if certificates are submitted which represent more Shares than are
tendered, certificates for such Shares not purchased or tendered will be
returned (or, in the case of Shares delivered by book-entry transfer within the
Book-Entry Transfer Facility pursuant to the procedures set forth in Section 2,
such Shares will be credited to an account maintained within the Book Entry
Transfer Facility) without expense to the tendering stockholder, as promptly as
practicable following the expiration, termination or withdrawal of the Offer.
Certificates representing Shares cancelled in the Merger will not be returned.

     If, prior to the Expiration Date, the Purchaser shall increase the
consideration offered to stockholders pursuant to the Offer, such increased
consideration shall be paid to all stockholders whose Shares are purchased
pursuant to the Offer.

     The Purchaser reserves the right to transfer or assign, in whole or from
time to time in part, with the consent of the Company, its right to purchase
Shares tendered pursuant to the Offer, but any such transfer or assignment will
not relieve the Purchaser of its obligations under the Offer and will not
prejudice the rights of tendering stockholders to receive payment for Shares
validly tendered and accepted for payment pursuant to the Offer.

5. CERTAIN FEDERAL INCOME TAX CONSIDERATIONS

     The following is a summary of certain United States Federal income tax
consequences of the receipt of cash for Shares pursuant to the Offer or the
Merger. This discussion is based on the Internal Revenue Code of 1986, as
amended (the 'Code'), judicial and administrative decisions thereunder, existing
temporary and proposed regulations and Internal Revenue Service rulings and
other pronouncements.

     THIS SUMMARY IS FOR GENERAL INFORMATION ONLY AND DOES NOT ADDRESS ALL
ASPECTS OF INCOME TAXATION THAT MAY BE RELEVANT TO STOCKHOLDERS. FOR EXAMPLE,
THIS DISCUSSION DOES NOT ADDRESS TAX CONSEQUENCES UNDER ANY APPLICABLE FOREIGN,
STATE, LOCAL OR OTHER TAX LAWS. IN ADDITION, THIS DISCUSSION DOES NOT ADDRESS
THE FEDERAL INCOME TAX CONSEQUENCES OF THE RECEIPT OF CASH FOR SHARES PURSUANT
TO THE OFFER OR THE MERGER TO PARTICULAR CATEGORIES OF TAXPAYERS SUBJECT TO
SPECIAL TREATMENT UNDER UNITED STATES FEDERAL INCOME TAX LAWS, SUCH AS TRUSTS,
FINANCIAL INSTITUTIONS, BROKER-DEALERS, PERSONS WHO ARE NOT CITIZENS OR
RESIDENTS OF THE UNITED STATES, TAX-EXEMPT ORGANIZATIONS, LIFE INSURANCE
COMPANIES, EMPLOYEES WHO ACQUIRED THEIR SHARES THROUGH THE EXERCISE OF AN
EMPLOYEE STOCK OPTION OR OTHERWISE AS COMPENSATION AND PERSONS WHO RECEIVED
PAYMENTS IN RESPECT OF OPTIONS TO ACQUIRE SHARES. EACH STOCKHOLDER SHOULD
CONSULT WITH SUCH STOCKHOLDER'S OWN TAX ADVISOR AS TO THE PARTICULAR TAX
CONSEQUENCES TO SUCH STOCKHOLDER OF THE RECEIPT OF CASH FOR SHARES PURSUANT TO
THE OFFER OR THE MERGER, INCLUDING THE CONSEQUENCES UNDER FEDERAL, STATE, LOCAL,
FOREIGN AND OTHER TAX LAWS.

     The receipt of cash for Shares pursuant to the Offer or the Merger will be
a taxable transaction for Federal income tax purposes. Generally, a stockholder
will recognize gain or loss in an amount equal to the difference between the
cash received and the stockholder's adjusted tax basis in the Shares. For

                                       10





<PAGE>

Federal income tax purposes, such gain or loss will be capital gain or loss if
the Shares are held as a capital asset by the stockholder, and long-term capital
gain or loss if the stockholder has held such Shares for more than one year,
measured as of the date the Purchaser accepts such Shares for payment pursuant
to the Offer or the Effective Time of the Merger, as the case may be.

     Under current law, capital gains recognized by individuals on capital
assets held for more than one year ('long-term capital gains') will be taxable
at a maximum rate of 20%.

     Capital losses are generally deductible only to the extent of capital gains
plus, in the case of noncorporate taxpayers, up to $3,000 of ordinary income.
Capital losses that do not offset capital gains or ordinary income as described
above may be carried forward to offset capital gains or up to $3,000 of ordinary
income per year in future years.

6. PRICE RANGE OF SHARES; DIVIDENDS

     The Shares are traded on the Nasdaq SmallCap Market and quoted under the
symbol 'ENDG' and on the Boston Stock Exchange under the symbol 'EDG.' For the
period from June 1, 1997 the table below sets forth, the high and low sale
prices per Share, as reported by the Nasdaq SmallCap Market. The prices set
forth below are as reported in published financial sources and do not include
retail markups, markdowns or commissions.

<TABLE>
<CAPTION>
                                                                                   HIGH               LOW

                          YEAR ENDED MAY 31, 1998
<S>                                                                           <C>               <C>
First Quarter..............................................................    4 5/8             3 1/8
Second Quarter.............................................................    6                 3 3/8
Third Quarter..............................................................    4 1/4             3 1/2
Fourth Quarter.............................................................    4 11/16           3 11/16

                          YEAR ENDED MAY 31, 1999
First Quarter..............................................................    4                 2 3/4
Second Quarter.............................................................    3 5/8             2 1/4
Third Quarter..............................................................    4 3/4             3 1/32
Fourth Quarter.............................................................    3 9/16            2

                         YEAR ENDING MAY 31, 2000
First Quarter (through June 1, 1999).......................................                3 9/16
</TABLE>

     On May 26, 1999, the last full trading day prior to the date of the
announcement of the Offer, the last sale price per Share as reported on the
Nasdaq SmallCap Market was $2.875. On June 1, 1999, the last trading day prior
to the date of this Offer to Purchase, the last sale price per Share as reported
on the Nasdaq SmallCap Market was $3.5625. Stockholders are urged to obtain
current market quotations for the Shares.

     The Company has never paid any cash dividends on the Shares. The Merger
Agreement provides that, without the prior written consent of Parent, the
Company will not declare, set aside or pay any dividend on or make any other
distribution in respect of any of its capital stock. See Section 12.

7. EFFECT OF THE OFFER ON THE MARKET FOR THE SHARES; NASDAQ AND BOSTON STOCK
   EXCHANGE QUOTATIONS; EXCHANGE ACT REGISTRATION; MARGIN REGULATIONS

     The purchase of Shares pursuant to the Offer will reduce the number of
holders of Shares and the number of Shares that might otherwise trade publicly
and could adversely affect the liquidity and market value of the remaining
Shares held by the public.

     Depending upon the number of Shares purchased pursuant to the Offer, the
Shares may no longer meet the requirements of the National Association of
Securities Dealers, Inc. (the 'NASD') for continued inclusion in the Nasdaq
SmallCap Market. Continued inclusion on Nasdaq generally requires (i) either at
least $2,000,000 in net tangible assets, a $35,000,000 market capitalization or
net income of at least $500,000 in two of the three prior years, (ii) at least
500,000 shares in the public float valued at

                                       11





<PAGE>

$1,000,000 or more, (iii) a minimum Common Stock bid price of $1.00, (iv) at
least two active market makers, and (v) at least 300 shareholders of Common
Stock. If these standards are not met, the Shares might nevertheless continue to
be included in The Nasdaq Stock Market with quotations published in the Nasdaq
'additional list' or in one of the 'local lists,' but if the number of holders
of the Shares were to fall below 300, or if the number of publicly held Shares
were to fall below 100,000 or there were not at least two registered and active
market makers for the Shares, the NASD's rules provide that the Shares would no
longer be 'qualified' for Nasdaq reporting and Nasdaq would cease to provide any
quotations. Shares held directly or indirectly by directors, officers or
beneficial owners of more than 10% of the Shares are not considered as being
publicly held for this purpose. According to the Company, as of May 26, 1999,
there were approximately 356 holders of record of Shares and 3,468,202 Shares
were outstanding. If, as a result of the purchase of Shares pursuant to the
Offer, the Shares no longer meet the requirements of the NASD for continued
inclusion in the Nasdaq SmallCap Market or The Nasdaq Stock Market, as the case
may be, the market for Shares could be adversely affected.

     In the event that the Shares no longer meet the requirements of the NASD
for quotation through Nasdaq and the Shares are no longer included in The Nasdaq
SmallCap Market, it is possible that, prior to the Effective Time, the Shares
would continue to trade in the over-the-counter market and that price quotations
would be reported by other sources. The extent of the public market for the
Shares and the availability of such quotations would, however, depend upon the
number of holders of Shares remaining at such time, the interests in maintaining
a market in Shares on the part of securities firms, the possible termination of
registration of the Shares under the Exchange Act, as described below, and other
factors.

     Similarly, depending upon the number of Shares purchased pursuant to the
Offer, the Shares may no longer meet the requirements of the Boston Stock
Exchange for continued listing on the Boston Stock Exchange. Continued listing
on the Boston Stock Exchange generally requires that companies have (i) at least
$1,000,000 in total assets, (ii) at least 150,000 shares in the public float
valued at $500,000 or more, (iii) at least 250 beneficial holders of Common
Stock, and (iv) stockholders equity of at least $500,000.

     The Shares are currently registered under the Exchange Act. Registration of
the Shares under the Exchange Act may be terminated upon application of the
Company to the Commission if the Shares are neither listed on a national
securities exchange nor held by 300 or more holders of record. Termination of
registration of the Shares under the Exchange Act would, subject to Section
15(d) of the Exchange Act, substantially reduce the information required to be
furnished by the Company to its stockholders and to the Commission and would
make certain provisions of the Exchange Act no longer applicable to the Company,
such as the short-swing profit recovery provisions of Section 16(b) of the
Exchange Act, the requirement of furnishing a proxy or information statement
pursuant to Section 14(a) or (c) of the Exchange Act in connection with
stockholders' meetings and the related requirement of furnishing an annual
report to stockholders and the requirements of Rule 13e-3 under the Exchange Act
with respect to 'going private' transactions. Furthermore, the ability of
'affiliates' of the Company and persons holding 'restricted securities' of the
Company to dispose of such securities pursuant to Rule 144 or 144A promulgated
under the Securities Act of 1933, as amended, may be impaired or eliminated.

     THE PURCHASER INTENDS TO SEEK TO CAUSE THE COMPANY TO APPLY FOR DELISTING
OF THE SHARES FROM THE NASDAQ SMALLCAP MARKET AND THE BOSTON STOCK EXCHANGE AND
TERMINATION OF REGISTRATION OF THE SHARES UNDER THE EXCHANGE ACT AS SOON AFTER
THE COMPLETION OF THE OFFER AS THE REQUIREMENTS FOR SUCH DELISTING AND/OR
TERMINATION ARE MET. IF REGISTRATION OF THE SHARES IS NOT TERMINATED PRIOR TO
THE MERGER, THEN THE REGISTRATION OF THE SHARES UNDER THE EXCHANGE ACT WILL BE
TERMINATED FOLLOWING THE CONSUMMATION OF THE MERGER.

     The Shares are currently 'margin securities' under the regulations of the
Board of Governors of the Federal Reserve System (the 'Federal Reserve Board'),
which has the effect, among other things, of allowing brokers to extend credit
on the collateral of the Shares. Depending upon factors similar to those
described above regarding listing and market quotations, it is possible that,
following the Offer, the Shares would no longer constitute 'margin securities'
for the purposes of the margin regulations of the Federal Reserve Board and
therefore could no longer be used as collateral for loans made by brokers. If
registration of Shares under the Exchange Act were terminated, the Shares would
no longer be 'margin securities.'

                                       12





<PAGE>

8. CERTAIN INFORMATION CONCERNING THE COMPANY

     The Company is a Massachusetts corporation with its principal executive
offices located at 30 Commerce Way, Woburn, Massachusetts 01801 and its
telephone number is (781) 937-0890. Except as otherwise set forth herein, the
information concerning the Company contained in this Offer to Purchase,
including financial information, has been furnished by the Company or has been
taken from or based upon publicly available documents and records on file with
the Commission and other public sources. Although neither Parent nor the
Purchaser has any knowledge that would indicate that statements contained herein
based upon such documents are untrue, none of the Purchaser, Parent, the Dealer
Manager, the Depositary or the Information Agent assumes any responsibility for
the accuracy or completeness of the information concerning the Company furnished
by the Company or contained in such documents and records or for the failure to
disclose events which may have occurred or may affect the significance or
accuracy of any such information but which are unknown to the Purchaser and
Parent.

     The Company is a supplier of specialty reagents, immuno-assay test kits and
molecular research products to customers involved in biomedical research, the
biotechnology industry and pharmaceutical drug discovery. The Company uses
monoclonal antibody and recombinant DNA technology to develop and manufacture
products in the field of cytokines, chemokines and related immune system
factors, the chemical messengers which convey signals within the immune system.

     Set forth below is certain selected consolidated financial information
excerpted from the information contained or incorporated by reference in the
Company's Annual Report on Form 10-KSB for the fiscal year ended May 31, 1998
(the 'Company 10-K') and the Company's Quarterly Report on Form 10-QSB for the
quarter ended February 28, 1999 (the 'Company 10-Q'). More comprehensive
financial information is included or incorporated by reference in the Company
10-K and the Company 10-Q, and the reports and other documents filed by the
Company with the Commission. The following summary is qualified in its entirety
by reference to such reports and other documents and all of the financial
information and notes contained therein. Such reports and other documents may be
examined at, and copies obtained from, the offices of the Commission in the
manner set forth below.

                                 ENDOGEN, INC.
                      SELECTED CONSOLIDATED FINANCIAL DATA

<TABLE>
<CAPTION>
                                                         FOR THE NINE MONTHS ENDED        FOR THE FISCAL YEAR ENDED
                                                                FEBRUARY 28,                       MAY 31,
                                                        ----------------------------    -----------------------------
                                                            1998            1999            1997             1998
                                                        ------------    ------------    -------------    ------------
                                                                (UNAUDITED)

<S>                                                     <C>             <C>             <C>              <C>
INCOME STATEMENT DATA
Revenue..............................................    $7,402,215      $7,469,232      $ 9,589,301     $ 10,033,451
Income (loss) from operations........................    $  438,118      $ (458,524)     $   737,107     $    509,166
Net income (loss)....................................    $  286,467      $ (461,511)     $   975,595     $    457,654
Basic earnings (loss) per share......................    $     0.08      $    (0.13)     $      0.32     $       0.13
Diluted earnings (loss) per share....................    $     0.08      $    (0.13)     $      0.29     $       0.13
Weighted average shares outstanding (basic)..........     3,429,452       3,452,980        3,095,262        3,432,590
Weighted average shares outstanding (diluted)........     3,634,221       3,452,980        3,394,662        3,626,311
</TABLE>

<TABLE>
<CAPTION>
                                                              FEBRUARY 28,       MAY 31,
                                                                  1999            1998
                                                              ------------     ----------
                                                              (UNAUDITED)

<S>                                                           <C>              <C>
BALANCE SHEET DATA
Working capital......................................          $3,590,443      $3,695,610
Total current assets.................................          $5,030,477      $4,991,689
Total assets.........................................          $7,563,273      $7,920,321
Term notes payable and capital lease obligations.....          $   85,287      $  202,919
Total stockholders' equity...........................          $6,037,952      $6,421,323
</TABLE>

                                       13





<PAGE>

     The Company is subject to the informational requirements of the Exchange
Act and in accordance therewith files reports, proxy statements and other
information relating to its business, financial condition and other matters with
the Commission. Certain information as of particular dates concerning the
Company's directors and officers, their compensation, Company Stock Options (as
defined below) granted to them, the principal holders of the Company's
securities and any material interest of such persons in transactions with the
Company is required to be disclosed in proxy statements distributed to the
Company's stockholders and filed with the Commission. Such reports, proxy
statements and other information should be available for inspection by anyone
without charge at the Public Reference Section of the Commission at Room 1024,
Judiciary Plaza, 450 Fifth Street, N.W., Washington, D.C. 20549, and at the
regional offices of the Commission located at Seven World Trade Center, Suite
1300, New York, New York 10048 and Citicorp Center, 500 West Madison Street,
Suite 1400, Chicago, Illinois 60661. Copies of such materials may be obtained
from the Public Reference Section of the Commission upon payment of prescribed
fees. The Commission also maintains a World Wide Web site on the internet at
http://www.sec.gov that contains reports and certain other information regarding
registrants that file electronically with the Commission, including the Company.
Such information should also be on file at The Nasdaq Stock Market, 1735 K
Street, N.W., Washington, D.C. 20006 and the Boston Stock Exchange, 100 Franklin
Street, Boston, Massachusetts 02110.

9. CERTAIN INFORMATION CONCERNING PERSTORP, THE PURCHASER AND PARENT

     Perstorp is a Swedish corporation engaged in the chemicals and materials
technology industry. Perstorp's shares are publicly traded and listed on the
Stockholm and London stock exchanges.

     Parent is a Swedish corporation engaged in the biotechnology and medical
technology industries. Parent was formerly operated as Perstorp's life science
division. All of the outstanding shares of capital stock of Parent are owned by
Perstorp. On April 24, 1999, at Perstorp's Annual General Meeting, the
shareholders of Perstorp voted to approve the board of directors' proposal that
all of the outstanding shares of capital stock of Parent will be spun off to
Perstorp's shareholders in late 1999.

     The Purchaser is a Massachusetts corporation formed solely for the purpose
of consummating the Offer and the Merger and carrying out related transactions.
Parent owns all of the outstanding shares of capital stock of the Purchaser. It
is not anticipated that the Purchaser will have any significant assets or
liabilities other than those arising under the Merger Agreement or in connection
with the Offer and the Merger, or engage in any activities other than those
incident to its formation and capitalization, the Offer and the Merger and
accordingly, no meaningful financial information regarding the Purchaser is
available. The address of the principal place of business of the Purchaser is
3747 North Meridian Road, Rockford, Illinois 61101 and its telephone number is
(815) 968-0747. The address of the principal place of business of Parent and
Perstorp is SE-284 80, Perstorp, Sweden and the telephone number is
011-46-435-380-00.

     Except as described in the discussion of the Merger Agreement and the
Stockholder Agreement in Section 12, none of the entities referred to above in
this Section 9 or any of their respective subsidiaries or, to the best of their
knowledge, any of the persons listed on Schedule I beneficially owns or has the
right to acquire any Shares, and none of such persons or entities has effected
any transactions in the Shares during the past 60 days. For certain information
concerning Perstorp, the Purchaser and Parent, see Schedule I hereto.

     Except as described in this Offer to Purchase, none of the entities
referred to above in this Section 9 or, to the best of their knowledge, any of
the persons listed on Schedule I, has any contract, arrangement, understanding
or relationship with any other person with respect to the securities of the
Company, including, but not limited to, any contract, arrangement, understanding
or relationship concerning the transfer or the voting of any such securities,
joint ventures, loan or option agreements, puts or calls, guarantees of loans,
guarantees against loss or the giving or withholding of proxies. Except as
described in this Offer to Purchase, none of the entities referred to above in
this Section 9 or, to the best of their knowledge, any of the persons listed on
Schedule I, has had, since January 1, 1995, any transactions with the Company or
any of its executive officers, directors or affiliates that would require
disclosure under the rules of the Commission. Except as described in this Offer
to Purchase, since such

                                       14





<PAGE>

date, there have been no contacts, negotiations or transactions between any of
the entities referred to in this Section 9 or, to the best of their knowledge,
any of the persons listed on Schedule I, and the Company or its affiliates
concerning a merger, consolidation or acquisition, a tender offer or other
acquisition of securities, an election of directors or a sale or other transfer
of a material amount of assets. None of the entities or persons referred to
above in this Section 9 or, to the best of their knowledge, any of the persons
listed on Schedule I, has had any relationship with the Company prior to the
commencement of discussions that led to the execution of the Merger Agreement.
Each of the entities referred to in this Section disclaims that it is an
'affiliate' of the Company within the meaning of Rule 13e-3 under the Exchange
Act.

     For certain information concerning the directors and executive officers of
the Purchaser, Parent and Perstorp, see Schedule I to this Offer to Purchase.

10. BACKGROUND OF THE OFFER; CONTACTS WITH THE COMPANY

     In January 1999, representatives of AH&H, the Company's financial
advisor, contacted the senior management of Pierce Chemical Company ('Pierce'),
an affiliate of the Purchaser and a wholly-owned subsidiary of the Parent, to
inquire as to Pierce's interest in pursuing a transaction with the Company.
Following this contact, Pierce initiated a review of certain publicly available
information concerning the Company and contacted representatives of AH&H to
advise them that Pierce would be interested in reviewing non-public information
about the Company and meeting with members of the Company's senior management.
On January 11, 1999, Pierce entered into a confidentiality agreement (the
'Confidentiality Agreement') with the Company.

     On February 16, 1999, representatives of Pierce met with certain members of
the Company's senior management regarding the business, strategies and prospects
of the Company.

     On March 23, 1999, representatives of Pierce and its financial advisor
Vector Securities International, Inc. ('Vector'), met with representatives of
the Company and AH&H and conducted a preliminary review of certain non-public
information. From March 23, 1999 through April 29, 1999, Pierce, Pierce's
advisors, the Company's senior management and the Company's advisors engaged in
various discussions regarding the business, strategies and prospects of the
Company and the possible terms of a potential transaction.

     On April 19, 1999, Vector, on behalf of Parent, submitted a non-binding
letter of interest to acquire all of the Shares for $3.00 per share in cash,
subject to, among other things, Parent completing a due diligence review of the
Company and the execution of a definitive agreement.

     During the weeks of April 19 and April 26, 1999, AH&H, on behalf of the
Company, led negotiations with Parent.

     On April 28, 1999, Vector, on behalf of Parent, submitted a revised
non-binding letter of interest to acquire all the Shares for $3.75
per Share in cash.

     On May 3, 1999, Pierce and its representatives continued their review of
the Company. On May 7, 1999 the Company's counsel received an initial draft
of the proposed Merger Agreement and the proposed Stockholder Agreement.
During the week of May 10, 1999 the Company's counsel and Parent's counsel
discussed a number of issues presented by the draft Merger Agreement and
draft Stockholder Agreement. Concurrently, management of Parent and the Company
began discussions of the continued employment of certain employees of the
Company.

      During these discussions, Parent insisted that the Company enter into
an exclusivity agreement before it would continue negotiations. The Exclusivity
Agreement was executed on May 12, 1999 and subsequently expired on May 22, 1999.

     During the week of May 17, 1999, AH&H and the Company's counsel, in
consultation with senior management and the Board of Directors, continued
to negotiate with Parent's counsel the terms and conditions of the proposed
Merger Agreement, including price, termination fee, representations and
warranties, covenants, termination provisions and conditions to the Offer.
During this period, Company counsel, in consultation with management and
the Board of Directors, also reviewed and continued to negotiate with
Parent's counsel the various terms of the Stock-holder Agreement.



                                       15





<PAGE>


     On May 24, 1999, Mr. Dempsey and several other employees of the Company
received draft employment agreements from Parent (the 'Employment Agreements'),
which Parent required to be entered into as a condition to entering into the
Merger Agreement. These employees of the Company retained counsel separate from
the Company's counsel to negotiate the Employment Agreements, and between May 24
and May 27, 1999, counsel to Parent and these employees, along with management
of Parent and these employees, negotiated the terms of the Employment
Agreements.

     Counsel for the Company and Parent continued the final negotiation of
the transaction documents. The Merger Agreement, the Stockholder Agreement
and the Employment Agreements were executed and a joint press release was
issued by the parties announcing the Merger Agreement on the morning of
May 27, 1999.

11. PURPOSE OF THE OFFER AND THE MERGER; PLANS FOR THE COMPANY; APPRAISAL RIGHTS

     The purpose of the Offer is to acquire control of, and the entire equity
interest in, the Company. Following the Offer, the Purchaser and Parent intend
to acquire any remaining equity interest in the Company not acquired in the
Offer by consummating the Merger.

     The MBCL requires, among other things, that the adoption of any plan of
merger or consolidation of the Company must be approved by the Board and
generally by the holders of the Company's outstanding voting securities. The
Board has approved the Offer and the Merger; consequently, the only additional
action of the Company that may be necessary to effect the Merger is approval by
such stockholders if the 'short-form' merger procedure described below is not
available. Under the MBCL, the affirmative vote of holders of two-thirds of the
outstanding Shares (including any Shares owned by the Purchaser) is generally
required to approve the Merger. If the Purchaser acquires, through the Offer or
otherwise, voting power with respect to at least two-thirds of the outstanding
Shares (which would be the case if the Minimum Condition were satisfied and the
Purchaser were to accept for payment Shares tendered pursuant to the Offer,
including the Shares subject to the Stockholder Agreement tendered by the
Selling Stockholders pursuant to the Offer), it would have sufficient voting
power to effect the Merger without the vote of any other stockholder of the
Company. However, the MBCL also provides that if a parent company owns at least
90% of each class of stock of a subsidiary, the parent company can effect a
short-form merger with that subsidiary without the action of the other
stockholders of the subsidiary. Accordingly, if, as a result of the Offer or
otherwise, the Purchaser acquires or controls the voting power of at least 90%
of the outstanding Shares, the Purchaser could, and intends to, effect the
Merger without prior notice to, or any action by, any other stockholder of the
Company.

     Plans for the Company. Except as otherwise set forth in this Offer to
Purchase, it is expected that, initially following the Merger, the business and
operations of the Company will be continued by the Surviving Corporation (as
defined below) substantially as they are currently being conducted. Parent
intends to operate the Company as a wholly owned subsidiary. Except as indicated
in this Offer to Purchase, Parent does not have any present plans or proposals
that relate to or would result in any material change in the Company's
capitalization or dividend policy or the composition of the Company's Board or
management. Parent and its affiliates regularly consider, and engage in
discussions concerning, potential investments in businesses, including
businesses that may be competitive with or complementary to the business of the
Company. There are currently no agreements with respect to an investment in any
such business. However, Parent may consider a merger, consolidation or other
extraordinary transaction involving the Company in connection with any such
investment.

     Parent will evaluate the business, operations, capitalization and
management of the Company during the pendency of the Offer and after
consummation of the Offer, and will take such actions as it deems appropriate
under the circumstances then existing with a view to optimizing the Company's
financial performance.

     The Merger Agreement provides that promptly upon the acceptance for payment
of, and payment for, any Shares by the Purchaser pursuant to the Offer, the
Purchaser shall be entitled to designate such number of the directors on the
Board such that the Purchaser, subject to compliance with Section 14(f) of the
Exchange Act, will control a majority of such directors, and the Company and its
Board shall, at



                                       16





<PAGE>

such time, take all such action needed to cause the Purchaser's designees to be
appointed to the Company's Board. Subject to applicable law, the Company has
agreed to take all action requested by Parent necessary to effect any such
election, including mailing to its stockholders the Information Statement
containing the information required by Section 14(f) of the Exchange Act and
Rule 14f-1 promulgated thereunder, which Information Statement is attached as
Annex A to the Schedule 14D-9. Parent's current intentions are to designate
Mats Fischier, a director of Parent, and the persons set forth in Schedule I
as directors of the Purchaser to serve on the Company's Board following
consummation of the Offer. In addition, following consummation of the Offer,
all of the current members of the Board will resign other than Owen A. Dempsey.
Parent's current intentions are that, immediately after the Effective Time, the
members of the Company Board immediately prior to the Effective Time, other
than Charles Granneman, will serve as directors of the Surviving Corporation,
and the initial officers of the Company will be the current officers of the
Company and such other persons as are designated by Parent.

     The Company has entered into the Employment Agreements, pursuant to which
certain employees will continue to serve in their current positions with the
Company after consummation of the Merger. See Section 12 'Employment
Agreements.'

     Appraisal Rights. Holders of Shares do not have dissenters' rights as a
result of the Offer. However, if the Merger is consummated, holders of Shares
will have certain rights pursuant to the provisions of Sections 85 through 98,
inclusive, of the MBCL to dissent in writing and demand appraisal of, and to
receive payment in cash of the 'fair value' (as such term is used in the MBCL)
of, their Shares. According to the provisions of Sections 85 through 98 of the
MBCL, the Parent and the dissenting holders of Shares may attempt to agree upon
the fair market value of their Shares. If the Parent and the dissenting holders
of the Shares fail to agree, and if the statutory procedures were complied with,
the dissenting holders of Shares could demand such rights could lead to a
judicial determination of the fair value required to be paid in cash to such
dissenting holders for their Shares. Any such judicial determination of the fair
value of Shares could be based upon considerations other than or in addition to
the Offer Price, the Merger Consideration or the market value of the Shares,
including asset values and the investment value of the Shares. The value so
determined could be more or less than the Offer Price or the Merger
Consideration.

     If any holder of Shares who demands appraisal under Sections 85 through 98,
inclusive, of the MBCL fails to perfect, or effectively withdraws or loses his
right to appraisal, as provided in the MBCL, the Shares of such stockholder will
be converted into the Merger Consideration in accordance with the Merger
Agreement. A stockholder may withdraw his demand for appraisal by delivery to
Parent of a written withdrawal of his demand for appraisal and acceptance of the
Merger.

     The foregoing discussion is not a complete statement of law pertaining to
appraisal rights under the MBCL and is qualified in its entirety by the full
text of Sections 85 through 98, inclusive of the MBCL.

     FAILURE TO FOLLOW THE STEPS REQUIRED BY SECTIONS 85 THROUGH 98, INCLUSIVE,
OF THE MBCL FOR PERFECTING APPRAISAL RIGHTS MAY RESULT IN THE LOSS OF SUCH
RIGHTS.

12. THE MERGER AGREEMENT; STOCKHOLDER AGREEMENT; EMPLOYMENT AGREEMENTS AND
    CONFIDENTIALITY AGREEMENT

THE MERGER AGREEMENT

     The Merger Agreement provides that following the satisfaction of the
conditions described below under 'Conditions to the Merger,' the Purchaser will
be merged with and into the Company, and each then outstanding Share (other than
Shares then owned by the Company, Parent, or any direct or indirect wholly owned
subsidiary of Parent or by stockholders, if any, who dissent from the Merger and
comply with all of the provisions of the MBCL concerning the right, if
applicable, of holders of Shares to seek appraisal of their Shares) will be
converted into the right to receive the price per Share paid in the Offer.

     The Offer. The Merger Agreement provides for the making of the Offer. The
obligation of the Purchaser to accept for payment or pay for Shares tendered
pursuant to the Offer is subject to the


                                       17





<PAGE>



satisfaction of the Minimum Condition and certain other conditions that are
described in Section 14. The Merger Agreement provides that the Purchaser may
extend the Offer by giving oral or written notice of such extension to the
Depositary, without the consent of the Company, only (1) if at the Expiration
Date any of the conditions to the Purchaser's obligations to accept Shares for
payment are not satisfied or waived, until such time as such conditions are
satisfied or waived (each individual extension not to exceed five (5) business
days after the previously scheduled Expiration Date), (2) for any period
required by any rule, regulation, interpretation or position of the Commission
or the staff thereof applicable to the Offer, and (3) on up to two occasions
in each case for period of not more than five (5) business days beyond the
latest Expiration Date if on such Expiration Date there shall have been tendered
more than the number of Shares sufficient to satisfy the Minimum Condition but
less than 90% of the Shares. In addition, the Purchaser has agreed in the Merger
Agreement that it will not, without the express written consent of the Company
and after giving oral or written notice of such extension to the Depositary,
(1) reduce the number of Shares subject to the Offer, (2) reduce the Offer
Price, (3) add to or modify the conditions set forth in Section 14, including
the Minimum Condition, (4) except as provided above, extend the Offer if all of
the conditions set forth in Section 14 are satisfied or waived, (5) change the
form of the consideration payable in the Offer or (6) amend or alter any term
of the Offer in any manner materially adverse to the Company's stockholders;
provided, however, that nothing contained in the Merger Agreement will prohibit
the Purchaser, in its sole discretion without the consent of the Company, from
waiving satisfaction of any condition of the Offer other than the Minimum
Condition.

     Pursuant to the Merger Agreement, the Company has granted the Purchaser the
Purchaser Stock Option, which is an irrevocable option to purchase the Option
Shares, which constitute up to 690,172 shares of Company Common Stock
representing approximately 19.9% of the Company's outstanding Common Stock
at a price per share equal to the Offer Price payable in cash. The Purchaser
Stock Option may be exercised, in whole or in part, at any time and from time
to time after the date on which the Purchaser has accepted for payment the
Shares tendered pursuant to the Offer and subject to satisfaction of the
Minimum Condition if, but only if, Parent and Purchaser agree to permanently
waive the Offer Conditions set forth in the Merger Agreement.

     The Merger. The Merger Agreement provides that, upon the terms and subject
to the conditions thereof, the Purchaser shall be merged with and into the
Company. As a result of the Merger, the separate corporate existence of the
Purchaser will cease and the Company will be the surviving corporation (the
'Surviving Corporation'). As a result of the Merger, each Share issued and
outstanding immediately prior to the Effective Time (other than Shares then
owned by the Company, Parent, the Purchaser or any other direct or indirect
wholly owned subsidiary of Parent, or by stockholders of the Company, if any,
who dissent from the Merger and comply with all the provisions of the MBCL
concerning the right, if applicable, of holders of Shares to seek appraisal of
their Shares) will be converted into the right to receive the Merger
Consideration. As a result of the Merger each issued and outstanding share of
capital stock of Purchaser will be automatically converted into one share of the
common stock of the Surviving Corporation.

     Termination of the Merger Agreement. The Merger Agreement may be terminated
at any time prior to the Effective Time, whether before or after approval of the
terms of the Merger Agreement by the stockholders of the Company, (1) by mutual
written consent of the Company and Parent, (2) by either the Company or Parent
if (a)(i) as a result of any of the conditions to the Offer not being satisfied,
the Offer shall have been terminated or expired in accordance with its terms
without the Purchaser having accepted for payment any Shares pursuant to the
Offer (including the Minimum Condition) or (ii) the Purchaser shall not have
accepted for payment any Shares pursuant to and subject to the conditions to the
Offer by July 31, 1999; provided, however, that the right to terminate the
Merger Agreement pursuant to clause (2)(a) will not be available to any party
whose failure to perform any of its obligations under the Merger Agreement
proximately contributed to the failure of any such condition or if the failure
of such condition results from facts or circumstances that constitute a breach
of any representation or warranty under the Merger Agreement by such party or
(b) if any Federal, state or local government or any court, tribunal,
administrative agency or commission or other regulatory authority or agency,
domestic, foreign or supranational (a 'Governmental Entity'), shall have issued
any order, decree or ruling or taken any action permanently enjoining,
restraining or otherwise



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<PAGE>




prohibiting the acceptance for payment of, or payment for, Shares pursuant to
the Offer or the Merger and such order, decree or ruling or other action has
become final and nonappealable, (3) by Parent or the Purchaser prior to the
Purchaser's obligation to accept Shares for payment pursuant to the Offer, in
the event of a material breach (as defined in the Merger Agreement) by the
Company of any representation, warranty, covenant or other agreement contained
in the Merger Agreement which would or reasonably would be expected to give rise
to the failure of a condition set forth in Section 14, (4) by Parent or the
Company if, prior to the obligation of the Purchaser to accept Shares for
payment pursuant to the Offer, the Company (i) amends the Schedule 14D-9 or
takes other action to modify its recommendation that the Offer and the Merger
are fair to and in the best interest of the Company and its stockholders and
its recommendation that the Company's stockholders accept the Offer, tender
their shares pursuant to the Offer and approve and adopt the Merger and the
Merger Agreement or (ii) enters into an acquisition agreement for an Alternative
Transaction (as defined below) that constitutes a Superior Proposal (as defined
below) and (5) by the Company if Parent or the Purchaser shall have (a) failed
to commence the Offer within five business days of the date of the Merger
Agreement, (b) failed to pay for Shares pursuant to the Offer in accordance
with the terms of the Merger Agreement or (c) breached in any material respect
any of their respective representations, warranties, covenants or other
agreements contained in the Merger Agreement, which breach or failure to
perform in respect of clause (c) is incapable of being cured or has not been
cured within 30 days after the giving of written notice to Parent or the
Purchaser, as applicable, except in any case under clause (c), such breaches
and failures which would not prevent the consummation of the Offer or the
Merger subject to the terms and conditions of the Merger Agreement.

     Alternative Transactions. The Merger Agreement provides that the Company
and its subsidiaries shall not, and shall not authorize or permit any of its
officers, directors or employees or any investment banker, financial advisor,
attorney, accountant or other representative retained by it to, directly or
indirectly, (1) solicit, initiate or furnish any information in response to any
inquiries or the making of any proposal that may lead to an Alternative
Transaction or (2) participate in any discussions or negotiations regarding any
Alternative Transaction; provided, however, that if, at any time prior to the
acceptance for payment of Shares pursuant to and subject to the conditions
(including the Minimum Condition) of the Offer, the Board determines in good
faith, after consultation with its outside counsel, that action is required by
reason of the Board's fiduciary duties under applicable law, the Company may
(subject to compliance with the notification provisions discussed below), in
response to an unsolicited Third Party Proposal, (a) furnish information with
respect to the Company to any person making such Third Party Proposal pursuant
to a confidentiality agreement that is at least as protective of the Company's
interest as is the Confidentiality Agreement and (b) participate in negotiations
regarding such Alternative Transaction.

     The Merger Agreement defines 'Third Party Proposal' as a bona fide proposal
from a third party, which proposal did not result from a breach of the
restrictions described above relating to a Third Party Proposal and which third
party the Board determines in good faith and upon the advice of AH&H or another
financial advisor of nationally recognized reputation to be reasonably capable
of completing a Superior Proposal. The Merger Agreement defines 'Alternative
Transaction' as any direct or indirect acquisition or purchase of assets of the
Company and its subsidiaries outside the ordinary course of business or
outstanding equity securities of the Company or any subsidiary, any tender offer
or exchange offer that if consummated would result in any person beneficially
owning equity securities of the Company or any merger, consolidation, business
combination, sale of substantially all the assets, recapitalization,
liquidation, dissolution or similar transaction that would result in the
acquisition of the Company or any subsidiary, other than the transactions
contemplated by the Merger Agreement and other than the acquisition of Shares
pursuant to the exercise of Company Stock Options or Warrants which are issued
and outstanding as of the date of the Merger Agreement.

     The Merger Agreement provides further that unless the Board shall have
terminated the Merger Agreement as described below, neither the Board nor any
committee thereof will (1) withdraw or modify, or propose to withdraw or modify,
the approval or recommendation by such Board or such committee of the Offer, the
Merger Agreement or the Merger, (2) approve or recommend, or propose to approve
or recommend, any Alternative Transaction or (3) cause the Company to enter into
any letter of intent, agreement in principle, acquisition agreement or other
agreement (an 'Acquisition


                                       19





<PAGE>



Agreement') with respect to any Alternative Transaction, unless in connection
with the taking of any action described in clause (1), (2) or (3) the Board
shall have previously terminated the Merger Agreement in connection with a
Superior Proposal (as set forth above in clause (4) of the section entitled
'Termination of the Merger Agreement'). Notwithstanding the preceding sentence,
if the Company's Board determines in its good faith judgment, after taking into
consideration the advice of its outside legal counsel, that it is required by
reason of their fiduciary duties under applicable law, the Company's Board of
Directors may: (A) withdraw its recommendation of the Offer or the Merger and
the other transactions contemplated thereby, or (B) approve or recommend or
cause the Company to enter into an agreement with respect to a Superior
Proposal; provided, however, that the Company concurrently terminates this
Agreement and pays the Parent a termination fee, including Expenses (as defined
below), in the amount of one million dollars ($1,000,000).

     The Merger Agreement defines a 'Superior Proposal' to be any Third Party
Proposal to acquire, directly or indirectly, all of the Shares or all or
substantially all of the assets of the Company; provided that (a) the Board
determines in its good faith judgment (after consulting with a financial advisor
of nationally recognized reputation) that such Third Party Proposal is on terms
that are more favorable to the Company's stockholders from a financial point of
view than the Offer and the Merger (taking into account all relevant factors,
including the amount and form of consideration to be received in respect of the
Shares, the relative value of any non-cash consideration and the timing and
certainty of closing), and (b) the Board determines in its good faith judgment
(after consultation with outside counsel) that the failure to recommend or
accept such Third Party Proposal would be required in order for its members to
comply with their fiduciary duties under applicable law.

     In addition to the obligations of the Company set forth in the preceding
paragraphs, the Merger Agreement provides that the Company as promptly as
reasonably practicable shall advise Parent orally and in writing of any request
for information or of any proposal or any inquiry regarding any Alternative
Transaction and the material terms and conditions of such request, proposal or
inquiry. The Company is further required under the terms of the Merger
Agreement, to the extent reasonably practicable and not in violation of the
Board's fiduciary duties under applicable law, after consultation with its
outside counsel, to keep Parent fully informed of the status and details
(including amendments or proposed amendments) of any such request, proposal or
inquiry. The Merger Agreement provides that nothing contained therein shall
prohibit the Company from taking and disclosing to its stockholders a position
contemplated by Rule 14e-2(a) promulgated under the Exchange Act or from making
any disclosure to the Company's stockholders with respect to any Third Party
Proposal if (1) in the good faith judgment of the Board, after consultation with
its outside counsel, such disclosure is required by reason of the Board's
fiduciary duties under applicable law and (2) the Company shall have provided
Parent and the Purchaser with reasonable advance notice of its position and
proposed disclosure under the circumstances; provided, however, that neither the
Company nor its Board nor any committee thereof is permitted, except as
permitted by the Merger Agreement, to withdraw or modify, or propose to withdraw
or modify, its position with respect to the Offer, the Merger or the Merger
Agreement or approve or recommend, or propose to approve or recommend, an
Alternative Transaction.

     Fees and Expenses. The Merger Agreement provides that in the event that the
Merger Agreement is terminated (1) by Parent or Purchaser pursuant to clause (3)
under the section above entitled 'Termination of the Merger Agreement,' (2) by
Parent pursuant to and in accordance with clause (2)(a)(i) under the section
above entitled 'Termination of the Merger Agreement' if such termination results
from the failure of the conditions described in clauses (c), (f) or (h) of
Section 14 entitled 'Certain Conditions of the Offer' as a result of any breach
by the Company of any covenant or agreement or any representation or warranty
made by the Company in the Merger Agreement or (3) pursuant to clause (4) under
the section above entitled 'Termination of the Merger Agreement,' the Company
shall promptly pay to Parent a termination fee, including all Expenses, in the
amount of one million dollars ($1,000,000). The Merger Agreement defines
'Expenses' as all out-of-pocket expenses incurred by the Purchaser and Parent in
connection with the Merger Agreement, the Stockholder Agreement and the
transactions contemplated thereby.

     Conduct of Business by the Company. The Merger Agreement provides that
during the term of the Merger Agreement, the Company shall, and shall cause each
of its subsidiaries to, carry on its business



                                       20





<PAGE>


in the ordinary course and use its best efforts to preserve intact its current
business organization, keep available the services of its current officers and
employees as appropriate and preserve its relationships with customers,
suppliers, licensors, licensees and others having business dealings with it.
The Merger Agreement further provides that, except as otherwise expressly
contemplated by the Merger Agreement or approved by Parent in writing (which
approval shall not be unreasonably withheld or delayed), the Company shall not
and shall cause its subsidiaries not to (1) (a) declare, set aside or pay any
dividends on, or make any other distributions in respect of, any of its capital
stock, (b) split, combine or reclassify any of its capital stock or issue or
authorize the issuance of any other securities in respect of, in lieu of or in
substitution for shares of its capital stock or (c) purchase, redeem or
otherwise acquire any shares of capital stock of the Company or any other
securities thereof or any rights, warrants or options to acquire any such
shares or other securities; (2) issue, deliver, sell, pledge or otherwise
encumber any shares of its capital stock, any other voting securities or any
securities convertible into, or any rights, warrants or options to acquire, any
such shares, voting securities or convertible securities (other than the
issuance of Shares upon the exercise of Company Stock Options or warrants to
purchase Shares outstanding on the date of the Merger Agreement in accordance
with their present terms); (3) amend its articles of organization or by-laws;
(4) acquire or agree to acquire (A) by merging or consolidating with, or by
purchasing a substantial portion of the assets of, or by any other manner, any
business or any corporation, partnership, joint venture, association or other
business organization or division thereof or (B) any assets except for the
purchase of assets for an amount which does not exceed, individually or in the
aggregate, $100,000; (5) sell, lease, license, mortgage or otherwise encumber or
subject to any lien or otherwise dispose of any of its properties or assets,
except sales of inventory or sales of immaterial assets; (6) (A) except for
certain existing indebtedness and certain short-term borrowings incurred in the
ordinary course of business, incur any indebtedness for borrowed money or
guarantee any such indebtedness of another person, issue or sell any debt
securities or warrants or other rights to acquire any debt securities of the
Company, guarantee any debt securities of another person, enter into any 'keep
well' or other agreement to maintain any financial statement condition of
another person or enter into any arrangement having the economic effect of any
of the foregoing or (B) make any loans, advances or capital contributions to, or
investments in, any other person; (7) make or agree to make any capital
expenditure or expenditures with respect to property, plant or equipment which,
individually, is in excess of $75,000 or, in the aggregate, are in excess of
$250,000; (8) except as required by law or as consistent with past practice,
make any tax election or settle or compromise any income tax liability or take
any action or position inconsistent with the past tax or accounting practices of
the Company; (9) with certain exceptions, pay, discharge, settle or satisfy any
claims, liabilities or obligations (absolute, accrued, asserted or unasserted,
contingent or otherwise), other than the payment, discharge or satisfaction, in
the ordinary course of business consistent with past practice or in accordance
with their terms, of liabilities reflected or reserved against in, the most
recent consolidated financial statements (or the notes thereto) of the Company
included in any report of the Company filed with the Commission and publicly
available prior to the date of the Merger Agreement or incurred thereafter in
the ordinary course of business consistent with past practice, or waive the
benefits of, or agree to modify in any material respect, any confidentiality,
standstill or similar agreement to which the Company or any subsidiary is a
party, (10) except in the ordinary course of business, modify, amend or
terminate any material contract, agreement, arrangement or other instrument
(including any amendments thereto) to which the Company or any of its
subsidiaries is a party or waive, release or assign any rights or claims; (11)
enter into any contracts, agreements, arrangements or instruments (including any
amendments thereto) relating to the distribution, sale or marketing by third
parties of the Company's or its subsidiaries' products or services or enter into
any such arrangement with any supplier of the Company unless terminable upon no
more than thirty (30) days notice; (12) except as required to comply with
applicable law and subject to exceptions for the Employment Agreements, (A)
adopt, enter into, terminate or amend any benefit plan or other arrangement for
the benefit or welfare of any director, officer or current or former employee,
(B) increase in any manner the compensation or fringe benefits of, or pay any
bonus to, any director, officer or employee (except for normal increases or
bonuses, in the ordinary course of business consistent with past practice), (C)
pay any benefit not provided for under any benefit plan other than bonuses in
the ordinary course of business consistent with past practice, (D) except as
permitted in clause (B), grant any awards under any bonus, incentive,
performance or other compensation plan or arrangement or benefit plan (including
the grant of stock options, stock



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<PAGE>


appreciation rights, stock based or stock related awards, performance units or
restricted stock, or the removal of existing restrictions in any benefit plans
or agreement or awards made thereunder) or (E) take any action other than in the
ordinary course of business to fund or in any other way secure the payment of
compensation or benefits under any employee plan, agreement, contract or
arrangement or benefit plan; or (13) authorize any of, or commit or agree to
take any of, the foregoing actions.

     Pursuant to the Merger Agreement, the Company shall not take any action or
omit to take any action, the taking or omission of which could reasonably be
expected to result in (1) any of its representations and warranties set forth in
the Merger Agreement becoming untrue or inaccurate in any material respect or
(2) any of the conditions to the Offer or to the Merger not being satisfied
(subject to exceptions specifically permitted by the Merger Agreement).

     Stock Options. The Merger Agreement provides that as soon as practicable
following the date of the Merger Agreement but in no event later than the
consummation of the Offer, the Company (or, if appropriate, the Board or any
committee administering the Stock Option Plans) shall (including by adopting
resolutions or taking any other actions) take action so as to allow that each
outstanding option to purchase Shares (a 'Company Stock Option') granted under
any stock option, stock appreciation rights or stock purchase plan, or other
right, program, arrangement or agreement of the Company (collectively, the
'Stock Option Plans') and each outstanding warrant to purchase Shares (a
'Warrant') in each case outstanding immediately prior to the date of the Merger
Agreement: (A) to the extent then exercisable, either (1) to be cancelled
immediately after consummation of the Offer in exchange for an amount in cash,
payable at the time of such cancellation, equal to the product of (x) the number
of Shares subject to such Company Stock Option or Warrant immediately prior to
the Effective Time and (y) the excess, if any, of the price per Share to be paid
in the Offer over the per Share exercise price of such Company Stock Option or
Warrant (the 'Net Amount') or (2) to be converted immediately prior to the
Effective Time into the right solely to receive the Net Amount; provided,
however, that no such cash payment has been made or (B) to the extent not then
exercisable, to be canceled immediately after consummation of the Offer. The
Company shall not make, or agree to make, any payment of any kind to any holder
of a Company Stock Option or a Warrant (except for the payment described above)
without the consent of Parent.

     The Merger Agreement provides further that subject to the provisions set
forth above, all Stock Option Plans and the Employee Stock Purchase Plan shall
terminate as of the Effective Time and the provisions in any other benefit plan
providing for the issuance, transfer or grant of any capital stock of the
Company or any interest in respect of any capital stock of the Company shall be
terminated as of the Effective Time. The Merger Agreement provides that the
Company shall ensure that following the Effective Time, no holder of a Company
Stock Option or Warrant nor any participant in any Stock Option Plan or the
Employee Stock Purchase Plan shall have any right thereunder to acquire any
capital stock of the Company, Parent or the Surviving Corporation, and that the
Company shall use its reasonable best efforts to ensure that following the
Effective Time, no holder of any remaining Company Stock Option or Warrant nor
any participant in any Stock Option Plan shall have any right thereunder to
acquire any capital stock of the Company, Parent or the Surviving Corporation.
The Merger Agreement also provides that the Surviving Corporation shall continue
to be obligated to pay the Net Amount to holders of any Company Stock Options or
Warrants converted in accordance with clause (y) of the immediately preceding
paragraph.

     Indemnification and Exculpation. Parent has agreed in the Merger Agreement
that all rights to indemnification and exculpation (including the advancement of
expenses) from liabilities for acts or omissions occurring at or prior to the
Effective Time (including with respect to the transactions contemplated by the
Merger Agreement) existing now or at the Effective Time in favor of the current
or former directors or officers of the Company as provided in its articles of
organization, its by-laws and certain indemnification agreements shall be
assumed by the Surviving Corporation in the Merger, without further action, as
of the Effective Time and shall survive the Merger and shall continue in full
force and effect without amendment, modification or repeal in accordance with
their terms; provided however, that if any claims are asserted or made within
such period, all rights to indemnification (and to advancement of expenses)
hereunder in respect of any such claims shall continue, without diminution,
until disposition of any and all such claims.



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<PAGE>


     Conditions to the Merger. The Merger Agreement provides that the Merger is
subject to the satisfaction or waiver of certain conditions, including the
following: (1) if required by applicable law, the Merger Agreement having been
approved and adopted by the affirmative vote of the Company's stockholders by
the requisite vote in accordance with applicable law and the Company's articles
of organization and (2) no statute, rule, regulation, executive order, decree,
temporary restraining order, preliminary or permanent injunction or other order
issued by any court of competent jurisdiction or other governmental entity or
other legal restraint or prohibition preventing the consummation of the Merger
being in effect; provided, however, that each of the Company, the Purchaser and
Parent has used reasonable efforts to prevent the entry of any such injunction
or other order and to appeal as promptly as possible any injunction or other
order that may be entered.

     Reasonable Efforts. The Merger Agreement provides that, on the terms and
subject to the conditions of the Merger Agreement, each of the parties will use
all reasonable efforts to take, or cause to be taken, all actions, and to do, or
cause to be done, and to assist and cooperate with the other parties in doing,
all things necessary, proper or advisable to consummate and make effective, in
the most expeditious manner practicable, the Offer and the Merger and the other
transactions contemplated by the Merger Agreement.

     Representations and Warranties. The Merger Agreement contains various
customary representations and warranties.

STOCKHOLDER AGREEMENT

     The Stockholder Agreement provides that each Selling Stockholder will
tender in the Offer, and the Purchaser will purchase, all Shares beneficially
owned by such Selling Stockholder (the 'Subject Shares'), at a price per Share
equal to the Offer Price. Such obligations regarding the Subject Shares are
subject to the prior satisfaction or waiver of (1) the Purchaser having accepted
Shares for payment under the terms of the Offer, (2) the Minimum Condition
having been satisfied, (3) all regulatory approvals required by any applicable
law, rule or regulation having been obtained and being final, and (4) there
shall exist no preliminary or permanent injunction, or any other order by any
court of competent jurisdiction, restricting, preventing or prohibiting either
the purchase or the delivery of Subject Shares.

     Each of the Selling Stockholders has agreed, until the Merger Agreement has
terminated, among other things, not to: (1) sell, transfer, give, pledge, assign
or otherwise dispose of, or enter into any contract, option or other arrangement
with respect to the sale, transfer, pledge, assignment or other disposition of,
the Subject Shares owned by such Selling Stockholder other than pursuant to the
terms of the Offer or the Merger or (2) enter into any voting arrangement,
whether by proxy, voting agreement or otherwise, in connection with, directly or
indirectly, any takeover proposal.

     Each of the Selling Stockholders has also agreed until the Stockholder
Agreement has terminated (and the Stockholder Agreement includes an irrevocable
proxy provision for the benefit of the Purchaser with respect to the Shares
subject to the Stockholder Agreement owned by each Selling Stockholder), (1) to
vote the Subject Shares at any meeting of stockholders of the Company called to
vote upon the Merger and the Merger Agreement or at any adjournment thereof or
in any other circumstances upon which a vote, consent or other approval
(including by written consent) with respect to the Merger and the Merger
Agreement is sought, in favor of the Merger, the adoption by the Company of the
Merger Agreement and the approval of the terms thereof and each of the other
transactions contemplated by the Merger Agreement; and (2) to vote such Shares
at any meeting of stockholders of the Company or at any adjournment thereof or
in any other circumstances upon which a Selling Stockholder's vote, consent or
other approval is sought, against (x) any Alternative Transaction, (y) any
amendment of the Company's articles of organization or by-laws or other proposal
or transaction involving the Company, which amendment or other proposal or
transaction would be reasonably likely to impede, frustrate, prevent or nullify
the Merger, the Merger Agreement or any of the other transactions contemplated
by the Merger Agreement or change in any manner the voting rights of each class
of the Company's common stock or (z) any action that would cause the Company to
breach any representation, warranty or covenant contained in the Merger
Agreement.



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<PAGE>


EMPLOYMENT AGREEMENTS

     The Purchaser has entered into employment agreements with certain employees
of the Company including Owen A. Dempsey, the President of the Company and
Christine A. Burns, the Vice President of Product Development and Technology
(the 'Employment Agreements'), pursuant to which such persons will serve the
Company after consummation of the Offer. The Employment Agreements were executed
as of May 27, 1999 and are not effective until the date that the Purchaser
accepts for payment the Shares as specified in Section 4 of this Offer to
Purchase. The initial term of each of the Employment Agreements is 2 years.

     Under the Employment Agreements, Mr. Dempsey will receive a base salary of
$160,000 per year and Ms. Burns will receive a base salary of $144,000 per year.
The Purchaser has agreed to provide each of Mr. Dempsey and Ms. Burns with a
yearly bonus pursuant to a bonus plan to be agreed upon by the Purchaser and
each of them within 90 days after the Employment Agreements become effective.
Under such bonus plans, Mr. Dempsey will be entitled to earn up to an additional
$60,000 per year and Ms. Burns will be entitled to earn up to an additional
$36,000 per year. In addition, the Purchaser has agreed to provide a yearly
vehicle allowance to Mr. Dempsey equivalent in value to $10,000 and to Ms. Burns
equivalent in value to $6,000.

     Under the Employment Agreements, each of Mr. Dempsey and Ms. Burns and the
Purchaser have the right to terminate the agreement upon providing notice of
such party's intention not to renew the agreement at least 90 days prior to the
expiration of the agreement's initial term. The Purchaser may terminate the
Employment Agreements at any time for cause. The Purchaser and each of Mr.
Dempsey and Ms. Burns have the right to terminate their Employment Agreements
without cause upon at least 6 months' notice. In addition, each of Mr. Dempsey
and Ms. Burns has the right to terminate his or her employment for good reason,
(such as a reduction in salary, a relocation of more than 50 miles away from the
Employee's current place of employment, or any significant adverse change in the
nature of the Employee's duties or responsibilities), upon at least 30 days'
notice to the Purchaser.

     If the Purchaser terminates the employment of Mr. Dempsey or Ms. Burns by
choosing not to renew their agreements after the initial term or by terminating
their employment without cause, Mr. Dempsey and Ms. Burns are entitled to
continue to receive their salary for 12 months after their employment is
terminated. If Mr. Dempsey terminates his employment for good reason, he is
entitled to continue to receive his salary for 6 months after his employment is
terminated. If Ms. Burns terminates her employment for good reason, she remains
entitled to continue to receive her salary for 12 months after her employment is
terminated.

CONFIDENTIALITY AGREEMENT

     Pierce Chemical Company, an affiliate of Purchaser and Parent, and the
Company have executed the Confidentiality Agreement, dated January 11, 1999,
pursuant to which Pierce Chemical Company agreed to protect and treat as
confidential certain information provided to it by or on behalf of the Company.
Pierce Chemical Company agreed to return to the Company all but 1 copy of any
confidential information provided to it and agreed that for a period of 2 years
after termination of the Confidentiality Agreement, it would not use or disclose
such confidential information as long as such information remains confidential.

     Each of the Merger Agreement, the Stockholder Agreement and the Employment
Agreements contains other terms and conditions. The foregoing description of
certain terms and provisions of such agreements and documents is qualified in
its entirety by reference to the text of such agreements, which are filed as
exhibits to the Purchaser's Schedule 14D-1 and are incorporated herein by
reference.

13. SOURCE AND AMOUNT OF FUNDS

     The total amount of funds required to purchase all of the outstanding
Shares and to purchase and cancel all of the Company Stock Options and Warrants
pursuant to the Offer and the Merger and to pay related fees and expenses, is
expected to be approximately $15.5 million. Consummation of the Offer is not
conditioned on the obtaining of financing.


                                       24





<PAGE>

     In order to fund the Offer, the Merger and the related fees and expenses,
the Purchaser will obtain approximately $15.5 million of equity financing from
Parent, which will obtain such funds pursuant to financing from the working
capital of Perstorp.

14. CERTAIN CONDITIONS OF THE OFFER

     Notwithstanding any other term of the Offer, the Purchaser shall not be
required to accept for payment or, subject to any applicable rules and
regulations of the Commission, including Rule 14e-1(c) under the Exchange Act
(relating to the Purchaser's obligation to pay for or return tendered Shares
after the termination or withdrawal of the Offer), to pay for any Shares
tendered pursuant to the Offer unless the Minimum Condition shall have been
satisfied. Furthermore, notwithstanding any other term of the Offer, the
Purchaser shall not be required to accept for payment or, subject as aforesaid,
to pay for any Shares not theretofore accepted for payment or paid for, and
except as otherwise provided in the Merger Agreement or under applicable law,
may terminate the Offer if, at any time on or after the date hereof and before
the acceptance of such Shares for payment or the payment therefor, any of the
following conditions exists and is continuing as of any Expiration Date (other
than as a result of any action or inaction of Parent or any of its subsidiaries
that constitutes a breach of the Merger Agreement):

          (a) there shall be instituted or pending by any person or Governmental
     Entity any suit, action or proceeding (i) challenging the acquisition by
     Parent or the Purchaser of any Shares under the Offer or pursuant to the
     Stockholder Agreement, seeking to restrain or prohibit the making or
     consummation of the Offer or the Merger or the performance of any of the
     other transactions contemplated by the Merger Agreement or the Stockholder
     Agreement (including the voting provisions thereunder), or seeking to
     obtain from the Company, Parent or the Purchaser any damages in connection
     with the aforesaid transactions that are material in relation to the
     Company, (ii) seeking to compel the Parent to dispose of or hold separate
     any material portion of the business or assets of the Company or Parent and
     its subsidiaries, taken as a whole, as a result of the Offer, (iii) seeking
     to impose material limitations on the ability of Parent or the Purchaser to
     acquire or hold, or exercise full rights of ownership of, any Shares to be
     accepted for payment pursuant to the Offer or purchased under the
     Stockholder Agreement, including, without limitation, the right to vote
     such Shares on all matters properly presented to the stockholders of the
     Company, or (iv) seeking to prohibit Parent or any of its subsidiaries from
     effectively controlling in any material respect any material portion of the
     assets, properties, business or operations of the Company and its
     subsidiaries taken as a whole.

          (b) there shall be any statute, rule, regulation, judgment, order,
     injunction or other restraint enacted, entered, enforced, promulgated or
     deemed applicable to the Offer or the Merger, or any other action shall be
     taken by any Governmental Entity or court, that is reasonably likely to
     result, directly or indirectly, in any of the consequences referred to in
     clauses (i) through (iv) of paragraph (a) above; provided, however, that
     each of Parent and the Purchaser shall have used reasonable efforts to
     prevent the entry of any such injunction or other court order and to appeal
     as promptly as possible any injunction or other court order that may be
     entered;

          (c) there shall have occurred and continue to exist as of any
     Expiration Date any change or event that, individually or in the aggregate
     with any other change or event, is materially adverse to the assets,
     properties, business, financial condition, results of operations or
     prospects of the Company and its subsidiaries, taken as a whole, or any
     occurrence that with notice or lapse of time or both could reasonably be
     expected to result in any such change or event;

          (d) there shall have occurred and continue to exist as of any
     Expiration Date (i) any general suspension of trading in, or limitation on
     prices for, securities on the New York Stock Exchange or the NASDAQ, (ii) a
     declaration of a banking moratorium or any suspension of payments in
     respect of banks in the United States or any limitation by federal or state
     authorities on the extension of credit by lending institutions, or a
     disruption of or other event materially adversely affecting the extension
     of credit by lending institutions, (iii) a commencement of a war or armed
     hostilities or other national or international calamity directly or
     indirectly involving the United States, which has and continues to
     materially adversely affect the trading of securities on the NYSE involving
     the United States or (iv) in the case of any of the foregoing existing at
     the time of the commencement of the Offer, a material acceleration or
     worsening thereof;


                                       25





<PAGE>

          (e) the representations and warranties of the Company set forth in the
     Merger Agreement shall not be true and correct at the date hereof and at
     the scheduled or extended Expiration Date as though made on or as of such
     date (except for representations and warranties made as of a specified
     date) but only if the respects in which the representations and warranties
     made by the Company are inaccurate would in the aggregate have a material
     adverse effect and if such breaches of representations or warranties have
     not been cured within five (5) business days of written notice to Company
     by Parent or Purchaser; provided, however that in no event shall Parent be
     obligated to extend the Offer for more than one five (5) business day
     extension or beyond July 1, 1999 in order to permit Company to cure any
     such breach. For purposes of this offer condition, 'material adverse
     effect' shall mean that claims, demands, liabilities and losses arising
     out of such inaccuracy will actually or may reasonably be expected to
     result in Losses suffered or incurred by the Company, the Parent or the
     Purchaser, when taken as a whole, in excess of $300,000.

          (f) the Company shall have failed to perform in any material respect
     any obligation or to comply in any material respect with any agreement or
     covenant of the Company to be performed or complied with by it under the
     Merger Agreement and such failure has a material adverse effect;

          (g) the Merger Agreement shall have been terminated in accordance with
     its terms; or

          (h) the Company's total stockholders equity as of May 31, 1999 shall
     not be at least Five Million Five Hundred Thousand Dollars ($5,500,000) as
     determined in accordance with Company's past practice consistently applied;

which in the reasonable judgment of Parent, in any such case, makes it
inadvisable to proceed with the Offer or acceptance for payment or payment
for the Shares.

     The foregoing conditions in (a) through (h) above other than conditions
(b) and (g) are for the sole benefit of the Purchaser and Parent and, subject
to the terms of the Merger Agreement, may be waived by the Purchaser and
Parent in whole or in part at any time and from time to time in their sole
discretion. The failure by Parent or the Purchaser at any time to exercise
any of the foregoing rights shall not be deemed a waiver of any such right,
the waiver of any such right with respect to particular facts and
circumstances shall not be deemed a waiver with respect to any other facts
and circumstances and each such right shall be deemed an ongoing right that
may be asserted at any time and from time to time, except as otherwise
provided in the Merger Agreement.

15. CERTAIN LEGAL MATTERS

STATE TAKEOVER LAWS

     The Company conducts business in a number of states throughout the United
States, several of which have adopted laws and regulations purporting, to
various degrees, to apply to offers to acquire securities of entities which are
organized or have substantial assets, securityholders, employees, a principal
executive office and/or a principal place of business therein. In Edgar v. MITE
Corporation, the Supreme Court of the United States invalidated on
constitutional grounds the Illinois Business Takeover Act, which, as a matter of
state securities law, made takeovers of corporations meeting certain
requirements more difficult. In CTS Corp. v. Dynamics Corp. of America, however,
the Supreme Court held that a state may, as a matter of corporate law and, in
particular, those laws concerning corporate governance, constitutionally
disqualify a potential acquiror from voting on the affairs of a target
corporation without prior approval of the remaining stockholders, provided that
such laws were applicable only under certain conditions, in particular, that the
corporation has a substantial number of stockholders in the state and is
incorporated there.

MASSACHUSETTS ANTI-TAKEOVER LAW

     Control Share Acquisitions. The Company's By-laws include a provision that
Chapter 110D of the Massachusetts General Laws will not apply to the Company.
This statute governs 'control share acquisitions' and provides, in general, that
if a stockholder acquires shares which would raise the voting power of the
acquiring stockholder to one-fifth or more of the total voting power of the
Company, then the shares acquired obtain voting rights only upon the
authorization from a majority of the stockholders other than the acquiring
stockholder. The stockholders of the Company may amend the Company's Articles of
Organization at any time to subject the Company to this statute prospectively by
a vote of a majority of the stock entitled to vote on such matter.


                                       26





<PAGE>

     Restrictions on Business Combinations. The Company is subject to the
provisions of Chapter 110F of the Massachusetts General Laws, an anti-takeover
law. In general, Chapter 110F prohibits a Massachusetts corporation with more
than 200 stockholders from engaging in a business combination with a holder of
5% or more of the voting stock of a corporation (an 'interested stockholder')
for three years after the shareholder becomes an interested shareholder, unless
the acquiror receives prior Board of Directors' approval, acquires 90% or more
of the outstanding shares (excluding stock controlled by management and certain
employee stock ownership plans) or receives approval at an annual or special
meeting from two-thirds of the shareholders (other than the interested
shareholder). The stockholders, by vote of a majority of the stock entitled to
vote thereon, may amend the Company's Articles of Organization to provide that
the Company will not be governed by Chapter 110F. Such amendment will not be
effective for twelve months after its adoption and will not apply to any
stockholder who became an interested shareholder prior to the date of adoption
of such amendment.

     Bid Regulation. The Company is subject to the provisions of Chapter 110C of
the Massachusetts Laws, an anti-takeover law known as the Massachusetts
Take-Over Bid Regulation Act. In general, Chapter 110C prohibits an entity from
acquiring more than 10% of any class of the issued and outstanding equity
securities of a corporation unless the Board of Directors of the target
corporation consents to the acquisition or such acquiring entity publicly
announces the terms of the proposed take-over bid and files with the Secretary
of State of Massachusetts, and with the target corporation, disclosure documents
pertaining to the transaction. Such public announcement and filings must be made
before the acquiring entity acquires, directly or indirectly, more than 5% of
the issued and outstanding equity securities of any class of the target
corporation, any of which were purchased within one year prior to the proposed
take-over bid. Courts, both at the state and federal level, have been reluctant
to enforce the Massachusetts Take-Over Bid Regulation Act. Such courts have
stated that the statute's one-year moratorium likely violates the Commerce
Clause of the United States Constitution. They also express concern that the
Massachusetts Take-Over Bid Regulation Act is preempted by the Williams Act. In
Hyde Park Partners LP v. Connelly, 839 F.2d 837 (1st Cir. 1988), the Court held
that the Massachusetts Take-Over Bid Regulation Act altered the balance set by
Congress by favoring management and changing the point at which a takeover
bidder's control intent must be made public.

     Due to the approval of the Merger Agreement by the Company's Board of
Directors, the restrictions described above in "Restrictions on Business
Combinations" and "Bid Regulation" are not applicable to the Offer and the
Merger.

     It is a condition of the Offer that no statute, rule, regulation or order
impose any material limitation on the ability of Parent, the Purchaser or any of
their subsidiaries effectively to exercise full rights of ownership of the
Shares, including, without limitation, the right to vote the Shares. In the
event of the failure of such condition of the Offer, the Purchaser may terminate
or amend the Offer. See Section 14.

ANTITRUST

     The Federal Trade Commission (the 'FTC') and the Antitrust Division of the
United States Department of Justice (the 'Antitrust Division') frequently
scrutinize the legality under the antitrust laws of transactions such as the
Purchaser's proposed acquisition of the Company. At any time before or after the
Purchaser's purchase of Shares pursuant to the Offer, the Antitrust Division or
the FTC could take such action under the antitrust laws as it deems necessary or
desirable in the public interest, including seeking to enjoin the purchase of
Shares pursuant to the Offer or the consummation of the Merger or seeking the
divestiture of Shares acquired by the Purchaser or the divestiture of
substantial assets of Parent or its subsidiaries, or the Company or its
subsidiaries. Private parties may also bring legal action under the antitrust
laws under certain circumstances. There can be no assurance that a challenge to
the Offer on antitrust grounds will not be made or, if such a challenge is made,
of the results thereof.

GOING-PRIVATE RULES

     The Merger will have to comply with any applicable Federal law operative at
the time. Rule 13e-3 promulgated under the Exchange Act is applicable to certain
'going private' transactions. The Purchaser does not believe that Rule 13e-3
will be applicable to the Merger if the Merger is consummated within one year
after the Expiration Date at the same per Share price as paid in the


                                       27





<PAGE>



Offer. Rule 13e-3 would require, if applicable, among other things, that certain
financial information concerning the Company, and certain information relating
to the fairness of the proposed transaction and the consideration offered to
minority stockholders in such transaction, be filed with the Commission and
disclosed to minority stockholders prior to the consummation of the transaction.

16. FEES AND EXPENSES

     The Dealer Manager, the Information Agent and the Depositary have been
retained by the Purchaser in connection with the Offer. The Information Agent
may contact holders of Shares by mail, telephone, telex, telegraph and personal
interview and may request brokers, dealers, banks, trust

companies and other nominees to forward the Offer material to beneficial owners.
The Dealer Manager, the Information Agent and the Depositary each will receive
reasonable and customary compensation for their services, will be reimbursed for
certain reasonable out-of-pocket expenses and will be indemnified against
certain liabilities and expenses in connection therewith, including certain
liabilities under the Federal securities laws. Additionally, Vector is the
financial advisor to Parent and, as such, will receive a fee upon completion of
the acquisition of the Company. Neither the Information Agent nor the Depositary
has been retained to make solicitations or recommendations in connection with
the Offer.

     No fees or commissions will be paid by or on behalf of the Purchaser to any
broker or dealer or other person (other than the Dealer Manager) for soliciting
tenders of Shares pursuant to the Offer. Brokers, dealers, commercial banks,
trust companies and other nominees will be reimbursed by the Purchaser for
reasonable expenses incurred by them in forwarding material to their customers.

17. MISCELLANEOUS

     The Offer is not being made to, nor will tenders be accepted from or on
behalf of, holders of Shares in any jurisdiction in which the making of the
Offer or the acceptance thereof would not be in compliance with the laws of such
jurisdiction. Neither the Purchaser nor Parent is aware of any jurisdiction in
which the making of the Offer or the tender of the Shares in connection
therewith would not be in compliance with the laws of such jurisdiction. If the
Purchaser or Parent becomes aware of any valid state law prohibiting the making
of the Offer or the acceptance of the Shares pursuant thereto in such state, the
Purchaser will make a good faith effort to comply with any such state statute or
seek to have such statute declared inapplicable to the Offer. If after such good
faith effort, the Purchaser cannot comply with any state statute, the Offer will
not be made to, nor will tenders be accepted from or on behalf of, the holders
of Shares in such state. If the securities laws of any jurisdiction require that
the Offer be made by a licensed broker or dealer, the Offer shall be deemed to
be made on behalf of the Purchaser by the Dealer Manager or one or more
registered brokers or dealers that are licensed under the laws of such
jurisdiction.

     NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY
REPRESENTATION ON BEHALF OF THE PURCHASER OR PARENT NOT CONTAINED IN THIS OFFER
TO PURCHASE OR IN THE LETTER OF TRANSMITTAL AND, IF GIVEN OR MADE, ANY SUCH
INFORMATION OR REPRESENTATION MUST NOT BE RELIED UPON AS HAVING BEEN AUTHORIZED.
NEITHER THE DELIVERY OF THIS OFFER TO PURCHASE NOR ANY PURCHASE PURSUANT TO THE
OFFER, SHALL, UNDER ANY CIRCUMSTANCES, CREATE ANY IMPLICATION THAT THERE HAS
BEEN NO CHANGE IN THE AFFAIRS OF PARENT, THE PURCHASER OR THE COMPANY SINCE THE
DATE AS OF WHICH INFORMATION IS FURNISHED OR THE DATE OF THIS OFFER TO PURCHASE.

     The Purchaser has filed with the Commission a Tender Offer Statement on
Schedule 14D-1 ('Purchaser's Schedule 14D-1') and exhibits thereto pursuant to
Rule 14d-3 under the Exchange Act, furnishing certain additional information
with respect to the Offer. In addition, the Company has filed with the
Commission a Solicitation/Recommendation Statement on Schedule 14D-9 (including
exhibits) pursuant to Rule 14d-9 under the Exchange Act. Such statements and any
amendments thereto, including exhibits, may be examined at, and copies may be
obtained from, the offices of the Commission in the manner set forth in Section
9 of this Offer to Purchase (except that copies are not available at the
regional offices of the Commission).

                                       28





<PAGE>

                                                                      SCHEDULE I

           DIRECTORS AND EXECUTIVE OFFICERS OF EWOK ACQUISITION CORP.

     The following sets forth the name, business address, present principal
occupation or employment and material occupations, positions, offices or
employment for the past five years and citizenship of each of the directors and
executive officers of the Purchaser. Unless otherwise specified herein, the
business address of each of the officers and directors of the Purchaser is 3747
North Meridian Road, Rockford, Illinois 61105. Each person referred to herein is
a citizen of the United States.

<TABLE>
<CAPTION>
                                                                    OFFICES AND
                         NAME                                      POSITIONS HELD
- ------------------------------------------------------   ----------------------------------

<S>                                                      <C>
Robb Anderson.........................................   President and Director
Charles Granneman.....................................   Treasurer, Secretary and Director
</TABLE>

     ROBB ANDERSON is the President of the Purchaser. Mr. Anderson serves as the
President of Pierce Chemical Company, an affiliate of Purchaser, and has served
as an officer of certain affiliates of Perstorp since 1978. Mr. Anderson is a
director of Purchaser and certain affiliates of Perstorp.

     CHARLES GRANNEMAN is the Treasurer and Secretary of the Purchaser. Mr.
Granneman has served as an officer of certain affiliates of Perstorp since 1988.

             DIRECTORS AND EXECUTIVE OFFICERS OF PERBIO SCIENCE AB

     The following sets forth the name, business address, present principal
occupation or employment and material occupations, positions, offices or
employment for the past five years and citizenship of each of the directors of
Parent. Parent does not have officers at this time and is being managed by its
Board of Directors. Unless otherwise specified herein, the business address of
each of the directors of Parent is SE-284 80, Perstorp, Sweden. Each person
referred to herein is a citizen of Sweden.

<TABLE>
<CAPTION>
                                                                                  OFFICES AND
                                     NAME                                        POSITIONS HELD
- ------------------------------------------------------------------------------   --------------

<S>                                                                              <C>
Torbjorn Clementz.............................................................      Director
Mats Fischier.................................................................      Director
Magnus Lindquist..............................................................      Director
</TABLE>

     TORBJORN CLEMENTZ is Vice President, Corporate Control of Perstorp Group.
From November 1997 to May 1999 he was Corporate Financial Controller of Perstorp
Group. From November 1996 to October 1997, Mr. Clementz was Group Controller of
Salinity Group UK and from November 1993 through October 1996, he served as
Group Controller of PEAB, Sweden.

     MATS FISCHIER is Division Manager of Perstorp Life Science, a part of the
Perstorp Group. Since 1996, Mr. Fischier has served in various capacities with
the Perstorp Group, including Division Manager of the Pernovo Division from
February 1997 to September 1998 and Division Manager of Perstorp Analytical from
January 1996 to February 1997. Prior thereto Mr. Fischier served as a Division
Manager of Nobel Industrier of Akzo Nobel.

     MAGNUS LINDQUIST is Chief Financial Officer of Perstorp AB. Prior to taking
on his current position, from September 1996 until May 1999 he served as Senior
Vice President, Corporate Control of Perstorp AB. From April 1993 through August
1996 he served as Chief Financial Officer of Stora Cell AB.

                                      S-1





<PAGE>

                DIRECTORS AND EXECUTIVE OFFICERS OF PERSTORP AB

     The following sets forth the name, business address, present principal
occupation or employment and material occupations, positions, offices or
employment for the past five years and citizenship of each of the directors and
executive officers of Perstorp AB, the ultimate parent of Purchaser and Parent.
Unless otherwise specified herein, the business address of each of the officers
and directors of Perstorp AB is SE-284 80, Perstorp, Sweden. Each person
referred to herein is a citizen of Sweden.

<TABLE>
<CAPTION>
                                                                         OFFICES AND
                       NAME                                            POSITIONS HELD
- ---------------------------------------------------  ---------------------------------------------------

<S>                                                  <C>
Urban Jansson......................................  Chairman of the Board
Ake Fredriksson....................................  President and Chief Executive Officer and Director
Magnus Lindquist...................................  Chief Financial Officer
Fredrik Arp........................................  Director
Gunnar Brock.......................................  Director
Christer Gardell...................................  Director
Finn Johnsson......................................  Director
Karl Lennart Wendt.................................  Director
Wilhelm Wendt......................................  Director
</TABLE>

     URBAN JANSSON is the Chairman of Scandic Hotels AB and the Deputy Chairman
of Investment AB Bure. Mr. Jansson has been the Chairman of Perstorp since April
1999. He is also a member of the Board of both SEB and SAS. From 1992 to June
1998, he was President and Chief Executive Officer of Forvaltnings AB Ratos.

     AKE FREDRIKSSON has been the President and Chief Executive Officer of
Perstorp AB since 1997. Prior to this, Mr. Fredriksson served as the Executive
Vice President of Perstorp AB, and as a Division Manager of Perstorp Chemicals
from September 1996 to January 1997. From 1990 to August 1996, he was a Business
Area Manager of Perstorp Chemicals.

     MAGNUS LINDQUIST is Chief Financial Officer of Perstorp AB. Prior to taking
on his current position, from September 1996 until May 1999 he served as Senior
Vice President, Corporate Control of Perstorp AB. From April 1993 through August
1996 he served as Chief Financial Officer of Stora Cell AB.

     FREDRIK ARP is the President and Chief Executive Officer of Trelleborg AB.
He was elected to the Board in April 1999. From June 1996 to January 1999, Mr.
Arp was Managing Director and Chief Executive Officer of PLM. Prior to this,
from 1989 to May 1996, he was the Executive Vice President of Trelleborg AB.

     GUNNAR BROCK is the President and Chief Executive Officer of Tetra Pak
Group. He was elected to the Board of Perstorp AB in 1996. From 1992 to August
1994, Mr. Brock was President and Chief Executive Officer of Alfa Laval.

     CHRISTER GARDELL is the Chief Executive Officer of AB Custos. He was
elected to the Board of Perstorp AB in 1997. From 1995 to 1996, Mr. Gardell was
a Partner at Nordic Capital. Prior thereto, Mr. Gardell was a Partner at
McKinsey & Company.

     FINN JOHNSSON has been the President of Molnlycke Health Care AB since
April 1998. He was elected to the Board in 1997. Before becoming President of
Molnlycke, Mr. Johnsson was the Managing Director of United Distillers in
London. From 1990 to 1994, he was President and Chief Executive Officer of
Euroc.

     KARL LENNART WENDT is the President of Gustafsborgs Sateri. He has been a
member of the Board of Perstorp AB since 1974.

     WILHELM WENDT is the President of Internal AB. Mr. Wendt was elected to the
Board of Perstorp in 1996.

                                      S-2





<PAGE>

     Manually signed facsimile copies of the Letter of Transmittal will be
accepted. The Letter of Transmittal, certificates for Shares and any other
required documents should be sent or delivered by each stockholder of the
Company or his or her broker, dealer, commercial bank, trust company or other
nominee to the Depositary at one of its addresses set forth below.

                          The Depositary for the Offer is:
                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                                          <C>                                     <C>
               By Hand:                           Overnight Courier:                           By Mail:
      Reorganization Department               Reorganization Department               Reorganization Department
      40 Wall Street, 46th Floor              40 Wall Street, 46th Floor              40 Wall Street, 46th Floor
         New York, N.Y. 10005                    New York, N.Y. 10005                    New York, N.Y. 10005
</TABLE>

            Facsimile Transmission (for Eligible Institutions only):
                                 (718) 234-5001

              Confirm Receipt of Guaranteed Delivery by Telephone:
                                 (718) 921-8200

     Any questions or requests for assistance may be directed to the Information
Agent or the Dealer Manager at their respective addresses and telephone numbers
set forth below. Additional copies of the Offer to Purchase, the Letter of
Transmittal and the Notice of Guaranteed Delivery may be obtained from the
Information Agent. Stockholders may also contact their local broker, dealer,
commercial bank, trust company or other nominee for assistance concerning the
Offer.

                   The Information Agent for the Offer is:

                        [Georgeson & Company Inc. Logo]

                               Wall Street Plaza
                               New York, NY 10005
                            (212) 440-9800 (Collect)
                        or Call Toll Free (800) 223-2064

                      The Dealer Manager for the Offer is:

                     Vector Securities International, Inc.
                              1751 Lake Cook Road
                                   Suite 350
                              Deerfield, IL 60015
                            (847) 374-3853 (Collect)










<PAGE>
                             LETTER OF TRANSMITTAL
                                       TO
                         TENDER SHARES OF COMMON STOCK
                                       OF
                                 ENDOGEN, INC.
                                       AT
                          $3.75 NET PER SHARE IN CASH
              PURSUANT TO THE OFFER TO PURCHASE DATED JUNE 2, 1999
                                       BY
                             EWOK ACQUISITION CORP.
                           A WHOLLY OWNED SUBSIDIARY
                                       OF
                               PERBIO SCIENCE AB

        THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
      NEW YORK CITY TIME, ON TUESDAY, JUNE 29, 1999, UNLESS THE OFFER IS
                       EXTENDED (THE 'EXPIRATION DATE').


                        The Depositary for the Offer is:
                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                                     <C>                                     <C>
               By Hand:                           Overnight Courier:                           By Mail:
      Reorganization Department               Reorganization Department               Reorganization Department
      40 Wall Street, 46th Floor              40 Wall Street, 46th Floor              40 Wall Street, 46th Floor
         New York, N.Y. 10005                    New York, N.Y. 10005                    New York, N.Y. 10005
</TABLE>

            Facsimile Transmission (for Eligible Institutions only):
                                 (718) 234-5001

              Confirm Receipt of Guaranteed Delivery by Telephone:
                                 (718) 921-8200

     DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET
FORTH ABOVE, OR TRANSMISSION OF INSTRUCTIONS VIA FACSIMILE TRANSMISSION OTHER
THAN AS SET FORTH ABOVE, WILL NOT CONSTITUTE A DELIVERY TO THE DEPOSITARY. YOU
MUST SIGN THIS LETTER OF TRANSMITTAL IN THE APPROPRIATE SPACE PROVIDED BELOW AND
COMPLETE THE SUBSTITUTE FORM W-9 SET FORTH BELOW.

     THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ
CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.

<PAGE>
                          DESCRIPTION OF SHARES TENDERED
                   (ATTACH SEPARATE SIGNED LIST IF NECESSARY)
<TABLE>
<CAPTION>
                                                                                           TOTAL NO. OF
                  NAME(S) AND ADDRESS(ES) OF HOLDER(S)                                        SHARES         NUMBER OF
       (PLEASE FILL IN, IF BLANK, EXACTLY AS NAME(S) APPEAR(S) ON          CERTIFICATE    REPRESENTED BY      SHARES
                            CERTIFICATE(S))                                NUMBER(S)(1)   CERTIFICATE(S)(1)  TENDERED(2)
<S>                                                                       <C>             <C>              <C>




                         TOTAL SHARES TENDERED
  (1) Need not be completed by Book-Entry Stockholders
  (2) Unless otherwise specified, it will be assumed that all Shares represented by the
      Certificates described above are being tendered. See Instruction 4.
</TABLE>

     This Letter of Transmittal is to be completed by stockholders of Endogen,
Inc. either if certificates for tendered Shares (as defined below) are to be
forwarded herewith or if delivery of Shares is to be made by book entry transfer
to an account maintained by the Depositary at The Depository Trust Company
('DTC') pursuant to the procedures set forth in Section 2 of the Offer to
Purchase (as defined below). Stockholders who deliver Shares by book-entry
transfer are referred to herein as 'Book-Entry Stockholders' and other
stockholders are referred to herein as 'Certificate Stockholders.' If a
stockholder desires to tender Shares pursuant to the Offer (as defined below)
and such stockholder's certificates for Shares are not immediately available or
the procedure for book-entry transfer cannot be completed on a timely basis or
time will not permit all required documents to reach the Depositary prior to the
Expiration Date, such stockholder's tender may nevertheless be effected by
complying with the guaranteed delivery procedure set forth in Section 2 of the
Offer to Purchase. See Instruction 2. DELIVERY OF DOCUMENTS TO DTC DOES NOT
CONSTITUTE DELIVERY TO THE DEPOSITARY.

               (BOX BELOW FOR USE BY ELIGIBLE INSTITUTIONS ONLY)

<TABLE>
<S>        <C>
[ ]        CHECK HERE IF TENDERED SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER TO THE DEPOSITARY'S ACCOUNT
           AT THE DEPOSITORY TRUST COMPANY AND COMPLETE THE FOLLOWING:

           Name of Tendering Institution  ......................................................................

           Account No.  ........................................................................................

           Transaction Code No.  ...............................................................................
</TABLE>

<PAGE>
<TABLE>
<S>        <C>
[ ]        CHECK HERE IF TENDERED SHARES ARE BEING DELIVERED PURSUANT TO A NOTICE OF GUARANTEED DELIVERY
           PREVIOUSLY SENT TO THE DEPOSITARY AND COMPLETE THE FOLLOWING:

           Name(s) of Registered Holder(s)  ....................................................................

           Window Ticket Number (if any)  ......................................................................

           Date of Execution of Notice of Guaranteed Delivery  .................................................

           Name of Institution that Guaranteed Delivery  .......................................................

           If delivery is by book-entry transfer: Name of Tendering Institution:  ..............................
           Account No.  ................................................................................. at DTC

           Transaction Code No.  ...............................................................................
</TABLE>

Ladies and Gentlemen:

     The undersigned hereby tenders to EWOK Acquisition Corp., a Massachusetts
corporation (the 'Purchaser') and a wholly owned subsidiary of PerBio Science
AB, a Swedish corporation ('Parent'), the above-described shares of Common
Stock, $.01 par value (the 'Shares'), of Endogen, Inc., a Massachusetts
corporation (the 'Company'), pursuant to the Purchaser's offer to purchase all
outstanding Shares at a purchase price of $3.75 per Share, net to the seller in
cash, without interest thereon, upon the terms and subject to the conditions set
forth in the Purchaser's Offer to Purchase dated June 2, 1999 (the 'Offer to
Purchase'), and this Letter of Transmittal (which together with any amendments
or supplements thereto constitute the 'Offer'), receipt of which is hereby
acknowledged. All capitalized terms used and not otherwise defined herein have
the meanings ascribed to them in the Offer to Purchase.

     Upon the terms and subject to the conditions of the Offer, subject to, and
effective upon, acceptance for payment of the Shares tendered herewith by the
Purchaser, the undersigned hereby sells, assigns and transfers to, or upon the
order of, the Purchaser all right, title and interest in and to all the Shares
that are being tendered hereby (and any and all other Shares or other securities
or rights issued or issuable in respect thereof on or after June 2, 1999), and
irrevocably constitutes and appoints the Depositary the true and lawful agent
and attorney-in-fact of the undersigned with respect to such Shares (and any
such other Shares or securities or rights), with full power of substitution
(such power of attorney being deemed to be an irrevocable power coupled with an
interest), (i) to deliver certificates for such Shares (and any such other
Shares or securities or rights) or transfer ownership of such Shares (and any
such other Shares or securities or rights) on the account books maintained by
the DTC together, in each case, with all accompanying evidences of transfer and
authenticity to, or upon the order of, the Purchaser, (ii) to present such
Shares (and any such other Shares or securities or rights) for transfer on the
Company's books and (iii) to receive all benefits and otherwise exercise all
rights of beneficial ownership of such Shares (and any such other Shares or
securities or rights), all in accordance with the terms of the Offer. In
addition, the undersigned shall promptly remit and transfer to the Depositary
for the account of the Purchaser any and all such other Shares, securities or
rights, accompanied by appropriate documentation of transfer; and, pending such
remittance or appropriate assurance thereof, the Purchaser shall, subject to
applicable law, be entitled to all rights and privileges as owner of such other
Shares, securities or rights and may withhold the entire purchase price, or
deduct from the purchase price, the amount of value thereof as determined by the
Purchaser in its sole discretion.

     The undersigned hereby represents and warrants that (i) the undersigned has
full power and authority to tender, sell, assign and transfer the Shares
tendered hereby (and any and all other Shares or other securities or rights
issued or issuable in respect of such Shares on or after June 2, 1999) and

<PAGE>
(ii) when such Shares (and any such other Shares or securities or rights) are
accepted for payment by the Purchaser, the Purchaser will acquire good,
marketable and unencumbered title thereto, free and clear of all liens,
restrictions, claims and encumbrances and the same will not be subject to any
adverse claim. The undersigned will, upon request, execute and deliver any
additional documents deemed by the Depositary or the Purchaser to be necessary
or desirable to complete the sale, assignment and transfer of the Shares
tendered hereby (and any and all such other Shares or securities or rights).

     All authority conferred or agreed to be conferred in this Letter of
Transmittal shall be binding upon the successors, assigns, heirs, executors,
administrators, trustees in bankruptcy and legal representatives of the
undersigned and shall not be affected by, and shall survive, the death or
incapacity of the undersigned. Except as stated in the Offer to Purchase, this
tender is irrevocable.

     The undersigned hereby irrevocably appoints designees of the Purchaser, and
each of them, as the undersigned's attorneys-in-fact and proxies in the manner
set forth herein, each with full power of substitution, to the full extent of
the undersigned's rights with respect to the Shares tendered by the undersigned
and accepted for payment by the Purchaser and with respect to any and all other
Shares or other securities or rights issued or issuable in respect of such
Shares on or after June 2, 1999. All such proxies shall be considered coupled
with an interest in the tendered Shares. Such appointment will be effective
when, and only to the extent that, the Purchaser accepts for payment Shares
tendered by the undersigned as provided in the Offer to Purchase. Upon such
acceptance for payment, all prior powers of attorney and proxies given by the
undersigned with respect to such Shares or other securities or rights will,
without further action, be revoked and no subsequent powers of attorney and
proxies may be given (and, if given, will not be deemed effective). The
designees of the Purchaser will thereby be empowered to exercise all voting and
other rights with respect to such Shares or other securities or rights in
respect of any annual, special or adjourned meeting of the Company's
stockholders, or otherwise, as they in their sole discretion deem proper. The
Purchaser reserves the right to require that, in order for Shares to be deemed
validly tendered, immediately upon the Purchaser's acceptance for payment of
such Shares, the Purchaser must be able to exercise full voting and other rights
with respect to such Shares and other securities or rights, including voting at
any meeting of stockholders then scheduled. The powers of attorney and proxies
granted hereby are irrevocable and are granted in consideration of the
acceptance for payment of such Shares in accordance with the terms of the Offer.

     The undersigned understands that the valid tender of Shares pursuant to any
of the procedures described in Section 2 of the Offer to Purchase and in the
Instructions hereto will constitute a binding agreement between the undersigned
and the Purchaser upon the terms and subject to the conditions of the Offer.

     Unless otherwise indicated herein under 'Special Payment Instructions,'
please issue the check for the purchase price and/or return any certificates for
Shares not tendered or accepted for payment in the name(s) of the registered
holder(s) appearing under 'Description of Shares Tendered.' Similarly, unless
otherwise indicated under 'Special Delivery Instructions,' please mail the check
for the purchase price and/or return any certificates for Shares not tendered or
accepted for payment (and accompanying documents, as appropriate) to the
address(es) of the registered holder(s) appearing under 'Description of Shares
Tendered.' In the event that both Special Delivery Instructions and Special
Payment Instructions are completed, please issue the check for the purchase
price and/or return any certificates for Shares not tendered or accepted for
payment (and any accompanying documents, as appropriate) in the name of, and
deliver such check and/or return such certificates (and any accompanying
documents, as appropriate) to, the person or persons so indicated. The
undersigned recognizes that the Purchaser has no obligation pursuant to Special
Payment Instructions to transfer any Shares from the name(s) of the registered
holder(s) thereof if the Purchaser does not accept for payment any of the Shares
so tendered.

<PAGE>

<TABLE>

<S>                                                 <C>

         SPECIAL DELIVERY INSTRUCTIONS
        (SEE INSTRUCTIONS 1, 5, 6 AND 7)

To be completed ONLY if certificates for Shares
not tendered or not accepted for payment and/or
the check for the purchase price of Shares
accepted for payment are to be issued in the
name of someone other than the undersigned.

Issue [ ]  Check [ ] Certificates to:

Name ...........................................
                 (PLEASE PRINT)

Address ........................................

 ...............................................
               (INCLUDE ZIP CODE)

 ...............................................
(TAXPAYER IDENTIFICATION OR SOCIAL SECURITY NO.)
      (COMPLETE SUBSTITUTE FORM W-9 BELOW)


                                                            SPECIAL PAYMENT INSTRUCTIONS
                                                          (SEE INSTRUCTIONS 1, 5, 6 AND 7)

                                                  To be completed ONLY if certificates for Shares
                                                  not tendered or not accepted for payment and/or
                                                  the check for the purchase price of Shares
                                                  accepted for payment are to be sent to someone
                                                  other than the undersigned or to the undersigned
                                                  at an address other than that above.

                                                  Issue [ ]  Check [ ] Certificates to:

                                                  Name ...........................................
                                                                   (PLEASE PRINT)

                                                  Address ........................................

                                                  ................................................
                                                                 (INCLUDE ZIP CODE)

                                                  ................................................
                                                  (TAXPAYER IDENTIFICATION OR SOCIAL SECURITY NO.)
                                                        (COMPLETE SUBSTITUTE FORM W-9 BELOW)
</TABLE>

<PAGE>
                  PLEASE COMLETE THE SUBSTITUTE FORM W-9 BELOW

<TABLE>
<S>                                                                                                           <C>
                                              PLEASE SIGN HERE
                            (TO BE COMPLETED BY ALL TENDERING HOLDERS OF SHARES
                   REGARDLESS OF WHETHER SHARES ARE BEING PHYSICALLY DELIVERED HEREWITH)

 ...........................................................................................................

 ...........................................................................................................
                             SIGNATURE(S) OF HOLDER(S) OR AUTHORIZED SIGNATORY

Dated:  ............................................................................................. , 1999

     Must be signed by the registered holder(s) of the Certificates tendered hereby exactly as their name(s)
appear(s) on the Share Certificate(s), or by person(s) authorized to become registered holder(s) by
endorsements and documents transmitted with this Letter of Transmittal. If signature is by a trustee,
executor, administrator, guardian, attorney-in-fact, officer of a corporation, agent or other person acting
in a fiduciary or representative capacity, please provide the following information and see Instruction 5.

Date  ......................................................................................................

Name(s)  ...................................................................................................
                                               (PLEASE PRINT)

Capacity (full title)  .....................................................................................

Address  ...................................................................................................

 ...........................................................................................................
                                            (INCLUDING ZIP CODE)

Area Code and Telephone Number  ............................................................................

Tax Identification or Social Security No.  .................................................................

                                            SIGNATURE GUARANTEE

                                      (SEE INSTRUCTIONS 1 AND 5 BELOW)

 ...........................................................................................................
                           (NAME OF ELIGIBLE INSTITUTION GUARANTEEING SIGNATURES)

 ...........................................................................................................
     (ADDRESS (INCLUDING ZIP CODE) AND TELEPHONE NUMBER (INCLUDING AREA CODE) OF ELIGIBLE INSTITUTION)

 ...........................................................................................................
                                           (AUTHORIZED SIGNATURE)

 ...........................................................................................................
                                               (PRINTED NAME)

 ...........................................................................................................
                                                  (TITLE)

 .................................................................................................... , 1999
                                                   (DATE)
</TABLE>

<PAGE>
                                  INSTRUCTIONS

             FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER

     1. GUARANTEE OF SIGNATURE. No signature guarantee is required on this
Letter of Transmittal if (a) this Letter of Transmittal is signed by the
registered holder of Shares (which term, for purposes of this document, includes
any participant in DTC's system whose name appears on a security position
listing as the owner of the Shares) tendered herewith and such registered holder
has not completed either the box entitled 'Special Delivery Instructions' or the
box entitled 'Special Payment Instructions' above or (b) such Shares are
tendered for the account of a firm that is a participant in the Securities
Transfer Agents Medallion Program or the New York Stock Exchange Medallion
Signature Guarantee Program or the Stock Exchange Medallion Program or by any
other 'eligible guarantor institution,' as such term is defined in Rule 17Ad-15
under the Securities Exchange Act of 1934, as amended (each, an 'Eligible
Institution'). In all other cases, all signatures on this Letter of Transmittal
must be guaranteed by an Eligible Institution. See Instruction 5 to this Letter
of Transmittal. If the certificates for Shares are registered in the name of a
person other than the signer of this Letter of Transmittal, or if payment is to
be made or certificates for Shares not tendered or not accepted for payment are
to be issued to a person other than the registered holder of the certificates
surrendered, the tendered certificates must be endorsed or accompanied by
appropriate stock powers, in either case signed exactly as the name or names of
the registered holders or owners appear on the certificates, with the signatures
on the certificates or stock powers guaranteed as aforesaid. See Instruction 5
to this Letter of Transmittal.

     2. REQUIREMENTS OF TENDER. This Letter of Transmittal is to be completed by
stockholders either if certificates are to be forwarded herewith or if delivery
of Shares is to be made pursuant to the procedures for book-entry transfer set
forth in Section 2 of the Offer to Purchase. For a stockholder validly to tender
Shares pursuant to the Offer, either (a) a properly completed and duly executed
Letter of Transmittal (or facsimile thereof), together with any required
signature guarantees (or an Agent's Message in connection with a book-entry
transfer of Shares) and any other documents required by this Letter of
Transmittal, must be received by the Depositary at one of its addresses set
forth herein and either certificates for tendered Shares must be received by the
Depositary at one of such addresses or such Shares must be delivered pursuant to
the procedure for book-entry transfer set forth in Section 2 of the Offer to
Purchase (and a Book-Entry Confirmation (as defined in the Offer to Purchase) is
received by the Depositary), in each case, on or prior to the Expiration Date,
or (b) the tendering stockholder must comply with the guaranteed delivery
procedure set forth in Section 2 of the Offer to Purchase. Pursuant to such
procedure, (a) such tender must be made by or through an Eligible Institution,
(b) a properly completed and duly executed Notice of Guaranteed Delivery,
substantially in the form provided by the Purchaser, must be received by the
Depositary, as provided in Section 2 of the Offer to Purchase, on or prior to
the Expiration Date and (c) the certificates for all tendered shares, in proper
form for transfer (or a Book-Entry Confirmation with respect to such Shares),
together with a properly completed and duly executed Letter of Transmittal (or
facsimile thereof), with any required signature guarantees and any other
documents required by this Letter of Transmittal, must be received by the
Depositary within three Nasdaq SmallCap Market trading days after the date of
execution of such Notice of Guaranteed Delivery, all as provided in Section 2 of
the Offer to Purchase.

     THE METHOD OF DELIVERY OF SHARES, THIS LETTER OF TRANSMITTAL AND ALL OTHER
REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH DTC, IS AT THE ELECTION AND RISK
OF THE TENDERING STOCKHOLDER. SHARES WILL BE DEEMED DELIVERED ONLY WHEN ACTUALLY
RECEIVED BY THE DEPOSITARY. IF DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN
RECEIPT REQUESTED, PROPERLY INSURED, IS RECOMMENDED. IN ALL CASES, SUFFICIENT
TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY. DELIVERY OF THIS LETTER OF
TRANSMITTAL AND ACCOMPANYING SHARES WILL BE DEEMED EFFECTIVE, AND RISK OF LOSS
WITH RESPECT TO SUCH LETTER OF TRANSMITTAL AND ACCOMPANYING CERTIFICATE(S) WILL
PASS, ONLY WHEN SUCH LETTER OF TRANSMITTAL AND ACCOMPANYING CERTIFICATE(S) ARE
ACTUALLY RECEIVED BY THE DEPOSITARY.

<PAGE>
     No alternative, conditional or contingent tenders will be accepted and no
fractional Shares will be purchased. All tendering stockholders, by execution of
this Letter of Transmittal (or facsimile thereof), waive any right to receive
any notice of the acceptance of their Shares for payment.

     3. INADEQUATE SPACE. If the space provided herein is inadequate, the
certificate numbers and/or the number of Shares should be listed on a separate
schedule attached hereto.

     4. PARTIAL TENDERS (APPLICABLE TO CERTIFICATE STOCKHOLDERS ONLY). If fewer
than all the Shares evidenced by any certificate submitted are to be tendered,
fill in the number of Shares that are to be tendered in the box entitled 'Number
of Shares Tendered.' In any such case, new certificate(s) for the remainder of
the Shares that were evidenced by the old certificate(s) will be sent to the
registered holder, unless otherwise provided in the appropriate box on this
Letter of Transmittal, as soon as practicable after the expiration of the Offer.
All Shares represented by certificates delivered to the Depositary will be
deemed to have been tendered unless otherwise indicated.

     5. SIGNATURES ON LETTER OF TRANSMITTAL, STOCK POWERS AND ENDORSEMENTS. If
this Letter of Transmittal is signed by the registered holder of the Shares
tendered hereby, the signature must correspond with the name as written on the
face of the certificate(s) without any change whatsoever.

     If any of the Shares tendered hereby are owned of record by two or more
joint owners, all such owners must sign this Letter of Transmittal.

     If any tendered Shares are registered in different names on several
certificates, it will be necessary to complete, sign and submit as many separate
Letters of Transmittal as there are different registrations of certificates.

     If this Letter of Transmittal or any certificates or stock powers are
signed by trustees, executors, administrators, guardians, attorneys-in-fact,
officers of corporations or others acting in a fiduciary or representative
capacity, such persons should so indicate when signing, and proper evidence
satisfactory to the Purchaser of their authority so to act must be submitted.

     When this Letter of Transmittal is signed by the registered holder(s) of
the Shares listed and transmitted hereby, no endorsements of certificates or
separate stock powers are required unless payment is to be made to, or
certificates for Shares not tendered or accepted for payment are to be issued
to, a person other than the registered owner(s). Signatures on such certificates
or stock powers must be guaranteed by an Eligible Institution.

     If the certificates for Shares are registered in the name of a person other
than the signer of this Letter of Transmittal, or if payment is to be made or
certificates for Shares not tendered or not accepted for payment are to be
issued to a person other than the registered holder of the certificates
surrendered, the tendered certificates must be endorsed or accompanied by
appropriate stock powers, in either case, signed exactly as the name or names of
the registered holders or owners appear on the certificates, with the signatures
on the certificates or stock powers guaranteed as aforesaid. See Instruction 1.
Signatures on such certificates or stock powers must be guaranteed by an
Eligible Institution.

     6. STOCK TRANSFER TAXES. The Purchaser will pay any stock transfer taxes
with respect to the transfer and sale of Shares to it or its order pursuant to
the Offer. If, however, payment of the purchase price is to be made to, or if
certificate(s) for Shares not tendered or accepted for payment are to be
registered in the name(s) of, any person(s) other than the registered owner(s),
or if tendered certificate(s) are registered in the name(s) of any person(s)
other than the person(s) signing this Letter of Transmittal, the amount of any
stock transfer taxes (whether imposed on the registered holder(s) or such other
person(s)) payable on account of the transfer to such other person(s) will be
deducted from the purchase price unless satisfactory evidence of the payment of
such taxes or exemption therefrom is submitted.

     EXCEPT AS PROVIDED IN THIS INSTRUCTION 6, IT WILL NOT BE NECESSARY FOR
TRANSFER TAX STAMPS TO BE AFFIXED TO THE CERTIFICATE(S) LISTED IN THIS LETTER OF
TRANSMITTAL.

     7. SPECIAL PAYMENT AND DELIVERY INSTRUCTIONS. If a check is to be issued in
the name(s) of, and/or certificate(s) for Shares not tendered or not accepted
for payment are to be returned to, a person other than the signer of this Letter
of Transmittal or if a check is to be sent and/or such certificates are to be

<PAGE>
returned to a person other than the signer of this Letter of Transmittal or to
an address other than that shown above, the appropriate boxes on this Letter of
Transmittal must be completed. Any stockholder(s) delivering Shares by
book-entry transfer may request that Shares not accepted for payment be credited
to such account maintained at a Book-Entry Transfer Facility as such
stockholder(s) may designate.

     8. WAIVER OF CONDITIONS. Subject to the terms of the Offer, the Purchaser
reserves the absolute right in its sole discretion to waive any of the specified
conditions of the Offer, in whole or in part, in the case of any Shares
tendered.

     9. SUBSTITUTE FORM W-9. In order to avoid 'backup withholding' of Federal
income tax on payments of cash pursuant to the Offer, a stockholder surrendering
Shares in the Offer must (a) provide the Depositary with such stockholder's
correct taxpayer identification number ('TIN') on Substitute Form W-9 below and
(b) certify under penalty of perjury that such TIN is correct and that such
stockholder is not subject to backup withholding. If a stockholder does not
provide its correct TIN or fails to provide the certifications described above,
the Internal Revenue Service ('IRS') may impose a penalty on such stockholder
and any payment of cash to such stockholder pursuant to the Offer may be subject
to backup withholding of 31%.

     Certain stockholders (including, among others, all corporations and certain
foreign individuals) are not subject to backup withholding. Noncorporate foreign
stockholders should complete and sign the main signature form and a Form W-8,
Certificate of Foreign Status, a copy of which may be obtained from the
Depositary, in order to avoid backup withholding.

     If backup withholding applies, the Depositary is required to withhold 31%
of any such payments made to the stockholder or other payee. Backup withholding
is not an additional income tax. Rather, the tax liability of persons subject to
backup withholding will be reduced by the amount of tax withheld, provided that
the required information is given to the IRS. If withholding results in an
overpayment of taxes, a refund may be obtained from the IRS.

     The box in Part 2 of the Substitute Form W-9 may be checked if the
tendering stockholder has not been issued a TIN but has applied for a TIN or
intends to apply for a TIN in the near future. If the box in Part 2 is checked,
the stockholder or other payee must also complete the Certificate of Awaiting
Taxpayer Identification Number below in order to avoid backup withholding.
Notwithstanding that the box in Part 2 is checked and the Certificate of
Awaiting Taxpayer Identification Number is completed, the Depositary will
withhold 31% on all payments made prior to the time a properly certified TIN is
provided to the Depositary. However, such amounts will be refunded to such
stockholder if a TIN is provided to the Depositary within 60 days.

     The stockholder is required to give the Depositary the TIN (e.g., social
security number or employer identification number) of the record owner of the
Shares or of the last transferee appearing on the transfers attached to, or
endorsed on, the Shares. If the Shares are in more than one name or are not in
the name of the actual owner, consult the enclosed 'Guidelines for Certification
of Taxpayer Identification Number on Substitute Form W-9' for additional
guidance on which number to report.

     10. REQUESTS FOR ASSISTANCE OR ADDITIONAL COPIES. Requests for additional
copies of the Offer to Purchase, this Letter of Transmittal, the Notice of
Guaranteed Delivery and the Guidelines for Certification of Taxpayer
Identification Number on Substitute Form W-9 should be directed to the
Information Agent at its address as set forth below. Questions or requests for
assistance may be directed to the Information Agent.

     IMPORTANT: THIS LETTER OF TRANSMITTAL OR A FACSIMILE THEREOF (TOGETHER WITH
CERTIFICATES FOR, OR A BOOK-ENTRY CONFIRMATION WITH RESPECT TO, TENDERED SHARES
WITH ANY REQUIRED SIGNATURE GUARANTEES AND ALL OTHER REQUIRED DOCUMENTS) MUST BE
RECEIVED BY THE DEPOSITARY, OR THE NOTICE OF GUARANTEED DELIVERY MUST BE
RECEIVED BY THE DEPOSITARY, ON OR PRIOR TO THE EXPIRATION DATE.

<PAGE>

<TABLE>
<S>                           <C>                                            <C>
                                PART 1. Please provide your substitute TIN   ...................................
                                in the box at the right and certify by             Social Security Number
                                signing and dating below.                    ...................................
                                                                               Employer Identification Number
                                PART 2. TIN Applied for: [ ]

                                CERTIFICATIONS -- Under the penalties of perjury, I certify that:
                                (1) The number shown on this form is my correct Taxpayer Identification Number
                                    (or I am waiting for a number to be issued to me),
                                (2) I am not subject to backup withholding because: (a) I am exempt from backup
                                    withholding, or (b) I have not been notified by the Internal Revenue Service
                                    ('IRS') that I am subject to backup withholding as a result of a failure to
                                    report all interest or dividends, or (c) the IRS has notified me that I am
                                    no longer subject to backup withholding, and
                                (3) any other information provided on this form is true and correct.

                                                          CERTIFICATION INSTRUCTIONS
                                You must cross out item (2) above if you have been notified by the IRS that you
                                are currently subject to backup withholding because of underreporting interest
                                or dividends on your tax returns. However, if after being notified by the IRS
                                that you are subject to backup withholding, you received another notification
                                from the IRS stating that you are no longer subject to backup withholding, do
                                not cross out such item (2).

                                SIGNATURE: ................................    DATE: .................... , 1999

SUBSTITUTE
FORM W-9
DEPARTMENT OF THE TREASURY
INTERNAL REVENUE SERVICE

PAYOR'S REQUEST FOR
TAXPAYER IDENTIFICATION
NUMBER ('TIN')
</TABLE>

     YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU CHECKED THE BOX IN PART
2 OF SUBSTITUTE FORM W-9, INDICATING YOU HAVE APPLIED FOR, AND ARE AWAITING
RECEIPT OF, YOUR TIN.

              CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER

I certify under penalties of perjury that a taxpayer identification number has
not been issued to me, and that I mailed or delivered an application to receive
a taxpayer identification number to the appropriate Internal Revenue Service
Center or Social Security Administration Office (or I intend to mail or deliver
an application in the near future). I understand that if I do not provide a
taxpayer identification number by the time of payment, 31 percent (31%) of all
payments made to me pursuant to this offer shall be retained until I provide a
tax identification number to the payor and that, if I do not provide my taxpayer
identification number within sixty (60) days, such retained amounts shall be
remitted to the IRS as backup withholding and 31 percent of all reportable
payments made to me thereafter will be withheld and remitted to the IRS until
I provide a taxpayer identification number.

SIGNATURE  ...................................... DATE  .......................


NOTE:  FAILURE TO COMPLETE AND RETURN THIS FORM MAY RESULT IN BACKUP WITHHOLDING
OF 31 PERCENT OF ANY CASH PAYMENTS. PLEASE REVIEW THE ENCLOSED GUIDELINES FOR
CERTIFICATION OF TAXPAYER IDENTIFICATION NUMBER ON SUBSTITUTE FORM W-9 FOR
ADDITIONAL DETAILS.

<PAGE>
     Questions and requests for assistance or additional copies of the Offer to
Purchase, this Letter of Transmittal and other tender offer materials may be
directed to the Information Agent or the Dealer Manager at their respective
addresses and telephone numbers as set forth below.

                       The Information Agent for the Offer is:

                         [Georgeson & Company Inc. Logo]

                               Wall Street Plaza
                               New York, NY 10005
                            (212) 440-9800 (Collect)
                        or Call Toll Free (800) 223-2064

                      The Dealer Manager for the Offer is:

                     Vector Securities International, Inc.
                              1751 Lake Cook Road
                                   Suite 350
                              Deerfield, IL 60015
                            (847) 374-3853 (Collect)










<PAGE>


                         NOTICE OF GUARANTEED DELIVERY
                                      FOR
                        TENDER OF SHARES OF COMMON STOCK
                                       OF
                                 ENDOGEN, INC.
                                       TO
                             EWOK ACQUISITION CORP.
                           A WHOLLY OWNED SUBSIDIARY
                                       OF
                               PERBIO SCIENCE AB
                                       AT
                          $3.75 NET PER SHARE IN CASH
                   (NOT TO BE USED FOR SIGNATURE GUARANTEES)

         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
NEW YORK CITY TIME, ON TUESDAY, JUNE 29, 1999, UNLESS THE OFFER IS EXTENDED (THE
'EXPIRATION DATE'). TENDERS MAY BE WITHDRAWN AT ANY TIME PRIOR TO THE EXPIRATION
                                     DATE.

     As set forth in Section 2 of the Offer to Purchase (as defined below), this
form or one substantially equivalent hereto must be used to accept the Offer (as
defined below) if certificates representing shares of Common Stock, $.01 par
value (the 'Shares'), of Endogen, Inc., a Massachusetts corporation (the
'Company'), are not immediately available or the procedures for book entry
transfer cannot be completed on a timely basis or time will not permit all
required documents to reach the Depositary on or prior to the Expiration Date
(as defined in Section 1 of the Offer to Purchase). This form may be delivered
by hand to the Depositary or transmitted by telegram, facsimile transmission or
mail to the Depositary and must include a guarantee by an Eligible Institution
(as defined in Section 2 of the Offer to Purchase) in the form set forth in this
Notice of Guaranteed Delivery. See Section 2 of the Offer to Purchase.

                        The Depositary for the Offer is:
                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                                     <C>                                     <C>
               By Hand:                           Overnight Courier:                           By Mail:
      Reorganization Department               Reorganization Department               Reorganization Department
      40 Wall Street, 46th Floor              40 Wall Street, 46th Floor              40 Wall Street, 46th Floor
         New York, N.Y. 10005                    New York, N.Y. 10005                    New York, N.Y. 10005
</TABLE>

            Facsimile Transmission (for Eligible Institutions only):
                                 (718) 234-5001

              Confirm Receipt of Guaranteed Delivery by Telephone:
                                 (718) 921-8200

DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS OTHER THAN AS SET
FORTH ABOVE, OR TRANSMISSION OF INSTRUCTIONS VIA FACSIMILE TRANSMISSION OTHER
THAN AS SET FORTH ABOVE, WILL NOT CONSTITUTE A DELIVERY TO THE DEPOSITARY.

This form is not to be used to guarantee signatures. If a signature on a Letter
of Transmittal is required to be guaranteed by an Eligible Institution under the
instructions thereto, such signature guarantee must appear in the applicable
space provided in the signature box on the Letter of Transmittal.





<PAGE>


Ladies and Gentlemen:

     Pursuant to the guaranteed delivery procedures set forth in Section 2 of
the Offer to Purchase, the undersigned hereby tenders to EWOK Acquisition Corp.,
a Massachusetts corporation (the 'Purchaser') and a wholly owned subsidiary of
PerBio Science AB ('Parent'), a Swedish corporation, the below described Shares
of Endogen, Inc., a Massachusetts corporation (the 'Company'), pursuant to the
Purchaser's offer to purchase all outstanding Shares at a purchase price of
$3.75 per share, net to the seller in cash, without interest thereon, upon the
terms and subject to the conditions set forth in the Purchaser's Offer to
Purchase dated June 2, 1999, and the related Letter of Transmittal, receipt of
which is hereby acknowledged.

                            PLEASE SIGN AND COMPLETE

   Number of Shares:  .......................................................

   Name(s) of Record Holder(s):  ............................................
                                             (PLEASE TYPE OR PRINT)
                                         ....................................

   Certificate Nos. (if available):  ........................................

   Address(es):  ............................................................

    .........................................................................
                               (INCLUDE ZIP CODE)

   Area Code and Tel. No.:  .................................................

   (Check box if Shares will be tendered by book-entry transfer):

   [ ] The Depository Trust Company

   Signature(s):   ..........................................................

                   ..........................................................

   Account Number:  .........................................................

   Dated:  ........................................................    , 1999





<PAGE>

                                   GUARANTEE
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)

     The undersigned, a member of a registered national securities exchange or
of the National Association of Securities Dealers, Inc., a commercial bank or
trust company having an office or correspondent in the United States that is a
member in good standing of the Securities Transfer Agents Medallion Program, the
New York Stock Exchange Medallion Signature Guarantee Program or the Stock
Exchange Medallion Program, or an 'eligible guarantor institution,' as such term
is defined in Rule 17Ad-15 under the Securities Exchange Act of 1934, as
amended, hereby guarantees to deliver to the Depositary either the certificates
representing the Shares tendered hereby, in proper form for transfer, or a
Book-Entry Confirmation (as defined in Section 2 of the Offer to Purchase) of a
transfer of such Shares, in any such case together with a properly completed and
duly executed Letter of Transmittal, or a manually signed facsimile thereof,
with any required signature guarantees, and any other documents required by the
Letter of Transmittal within three Nasdaq SmallCap Market trading days after the
date hereof.

<TABLE>
<S>                                                     <C>
 .....................................................  ......................................................
                    (NAME OF FIRM)                                        (AUTHORIZED SIGNATURE)
 .....................................................  Name: ................................................
                      (ADDRESS)                                           (PLEASE TYPE OR PRINT)
 .....................................................  Title: ...............................................
               (CITY, STATE, ZIP CODE)
 .....................................................
           (AREA CODE AND TELEPHONE NUMBER)
</TABLE>

NOTE: DO NOT SEND CERTIFICATES FOR SHARES WITH THIS NOTICE. SHARE CERTIFICATES
SHOULD BE SENT WITH YOUR LETTER OF TRANSMITTAL.







<PAGE>


                               OFFER TO PURCHASE
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                                 ENDOGEN, INC.
                                       AT
                          $3.75 NET PER SHARE IN CASH
                                       BY
                             EWOK ACQUISITION CORP.
                           A WHOLLY OWNED SUBSIDIARY
                                       OF
                               PERBIO SCIENCE AB

         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
       NEW YORK CITY TIME, ON TUESDAY, JUNE 29, 1999, UNLESS THE OFFER IS
       EXTENDED (THE 'EXPIRATION DATE'). TENDERS MAY BE WITHDRAWN AT ANY
                       TIME PRIOR TO THE EXPIRATION DATE.

June 2, 1999

To Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees:

     We have been appointed by EWOK Acquisition Corp., a Massachusetts
corporation (the 'Purchaser') and a wholly owned subsidiary of PerBio Science AB
('Parent'), to act as Dealer Manager in connection with the Purchaser's offer to
purchase all outstanding shares of Common Stock, $.01 par value (the 'Shares'),
of Endogen, Inc., a Massachusetts corporation (the 'Company'), at a purchase
price of $3.75 per Share, net to the seller in cash, without interest thereon,
upon the terms and subject to the conditions set forth in the Purchaser's Offer
to Purchase dated June 2, 1999 (the 'Offer to Purchase'), and the related Letter
of Transmittal (which together constitute the 'Offer') enclosed herewith. The
Offer is being made pursuant to an Agreement and Plan of Merger dated as of May
27, 1999 (the 'Merger Agreement'), among Parent, the Purchaser and the Company.
All capitalized terms used and not otherwise defined herein shall have the
meanings ascribed to them in the Offer to Purchase.

     Please furnish copies of the enclosed materials to those of your clients
for whom you hold Shares registered in your name or in the name of your nominee.
Enclosed herewith are copies of the following documents:

          1. The Offer to Purchase dated June 2, 1999;

          2. The Letter of Transmittal to be used by stockholders of the Company
     accepting the Offer and tendering Shares pursuant thereto;

          3. The Letter to Stockholders of the Company, accompanied by the
     Company's Solicitation/Recommendation Statement on Schedule 14D-9;

          4. A letter that may be sent to your clients for whose account you
     hold Shares in your name or in the name of your nominee, with space
     provided for obtaining such client's instructions with regard to the Offer;

          5. The Notice of Guaranteed Delivery to be used to accept the Offer if
     the certificates evidencing Shares are not immediately available or the
     procedures for book-entry transfer cannot be completed on a timely basis or
     time will not permit all required documents to reach the Depositary on or
     prior to the Expiration Date (as defined in Section 1 of the Offer to
     Purchase);

          6. Guidelines of the Internal Revenue Service for Certification of
     Taxpayer Identification Number on Substitute Form W-9; and

          7. A return envelope addressed to the Depositary.




<PAGE>


     WE URGE YOU TO CONTACT YOUR CLIENTS PROMPTLY. PLEASE NOTE THAT THE OFFER
AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON
TUESDAY, JUNE 29, 1999, UNLESS THE OFFER IS EXTENDED.

     THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN ON OR PRIOR TO THE EXPIRATION DATE THAT NUMBER OF
OUTSTANDING SHARES WHICH, TOGETHER WITH THE OUTSTANDING SHARES SUBJECT TO THE
STOCKHOLDER AGREEMENT THAT SHALL NOT HAVE BEEN SO TENDERED, WOULD REPRESENT AT
LEAST TWO-THIRDS OF ALL OUTSTANDING SHARES ON A FULLY DILUTED BASIS (AS DEFINED
IN THE OFFER TO PURCHASE). THE OFFER IS NOT CONDITIONED ON OBTAINING FINANCING.

     THE OFFER IS ALSO SUBJECT TO OTHER TERMS AND CONDITIONS CONTAINED IN THE
OFFER TO PURCHASE. SEE THE INTRODUCTION AND SECTIONS 1, 12, 14 AND 15 OF THE
OFFER TO PURCHASE.

     The Board of Directors of the Company has approved the Merger Agreement and
has determined that the Offer and the Merger are fair to and in the best
interests of the stockholders of the Company and recommends that all of the
stockholders of the Company accept the Offer, tender their Shares and approve
the Merger Agreement and the Merger, if required by law.

     Upon the terms and subject to the conditions of the Offer (including, if
the Offer is extended or amended, the terms and conditions of the Offer as so
extended or amended), the Purchaser will purchase, by accepting for payment, and
will pay for all Shares validly tendered on or prior to the Expiration Date and
not properly withdrawn (in accordance with the procedures set forth in Section 3
of the Offer to Purchase), promptly after the Expiration Date. Payment for
Shares accepted for payment pursuant to the Offer will be made only after timely
receipt by the Depositary of (i) certificates for Shares (or Book-Entry
Confirmation) pursuant to the procedures set forth in Section 2 of the Offer to
Purchase, (ii) a Letter of Transmittal (or a facsimile copy thereof), properly
completed and duly executed, or an Agent's Message, and (iii) any other
documents required by the Letter of Transmittal.

     Neither the Purchaser nor Parent will pay any fees or commissions to any
broker or dealer or other person (other than the Dealer Manager, the Depositary
and Georgeson & Company, Inc., the Information Agent, as described in the Offer
to Purchase) for soliciting tenders of Shares pursuant to the Offer. You will be
reimbursed upon request for reasonable expenses incurred by you in forwarding
the enclosed offering materials to your customers.

     The Purchaser will pay or cause to be paid any stock transfer taxes payable
on the transfer of Shares to it, except as otherwise provided in Instruction 6
of the Letter of Transmittal.

     Any inquiries you may have with respect to the Offer should be addressed
to, and additional copies of the enclosed material may be obtained from,
Georgeson & Company, Inc., the Information Agent, at Wall Street Plaza, New
York, NY 10005, (212) 440-9800 (collect) or toll free at (800) 223-2064, or
Vector Securities International, Inc., the Dealer Manager, at 1751 Lake Cook
Road, Suite 350, Deerfield, IL 60015, (847) 374-3853 (Collect).

                                          Very truly yours,

                                          VECTOR SECURITIES INTERNATIONAL, INC.

NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL RENDER YOU OR ANY
OTHER PERSON THE AGENT OF THE PURCHASER, PARENT, THE DEALER MANAGER, THE
DEPOSITARY, THE INFORMATION AGENT OR ANY AFFILIATE THEREOF OR AUTHORIZE YOU OR
ANY OTHER PERSON TO GIVE ANY INFORMATION OR USE ANY DOCUMENT OR MAKE ANY
STATEMENTS ON BEHALF OF ANY OF THEM WITH RESPECT TO THE OFFER OTHER THAN THE
ENCLOSED DOCUMENTS AND THE STATEMENTS CONTAINED THEREIN.










<PAGE>


                               OFFER TO PURCHASE
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                                 ENDOGEN, INC.
                                       AT
                          $3.75 NET PER SHARE IN CASH
                                       BY
                             EWOK ACQUISITION CORP.
                           A WHOLLY OWNED SUBSIDIARY
                                       OF
                               PERBIO SCIENCE AB

         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
       NEW YORK CITY TIME, ON TUESDAY, JUNE 29, 1999, UNLESS THE OFFER IS
       EXTENDED (THE 'EXPIRATION DATE'). TENDERS MAY BE WITHDRAWN AT ANY
                       TIME PRIOR TO THE EXPIRATION DATE.

June 2, 1999

To Our Clients:

     Enclosed for your consideration is an Offer to Purchase dated June 2, 1999
(the 'Offer to Purchase'), and a related Letter of Transmittal (which together
constitute the 'Offer') relating to an offer by EWOK Acquisition Corp., a
Massachusetts corporation (the 'Purchaser') and a wholly owned subsidiary of
PerBio Science AB, a Swedish corporation ('Parent'), to purchase shares of
Common Stock, $.01 par value (the 'Shares'), of Endogen, Inc., a Massachusetts
corporation (the 'Company'), at a purchase price of $3.75 per Share, net to the
seller in cash, without interest thereon, upon the terms and subject to the
conditions set forth in the Offer. Also enclosed is the Letter to Stockholders
of the Company accompanied by the Company's Solicitation/Recommendation
Statement on Schedule 14D-9. All capitalized terms used but not otherwise
defined herein shall have the meanings ascribed to them in the Offer to
Purchase.

     THIS MATERIAL IS BEING SENT TO YOU AS THE BENEFICIAL OWNER OF THE SHARES
HELD BY US FOR YOUR ACCOUNT BUT NOT REGISTERED IN YOUR NAME. WE ARE THE HOLDER
OF RECORD OF SHARES HELD BY US FOR YOUR ACCOUNT. A TENDER OF SUCH SHARES CAN BE
MADE ONLY BY US AS THE HOLDER OF RECORD AND PURSUANT TO YOUR INSTRUCTIONS. THE
LETTER OF TRANSMITTAL IS FURNISHED TO YOU FOR YOUR INFORMATION ONLY AND CANNOT
BE USED TO TENDER SHARES HELD BY US FOR YOUR ACCOUNT.

     We request instructions as to whether you wish to tender any of or all the
Shares held by us for your account, pursuant to the terms and conditions set
forth in the Offer.

     Your attention is directed to the following:

          1. The tender price is $3.75 per Share, net to the seller in cash,
     without interest thereon.

          2. THE BOARD OF DIRECTORS OF THE COMPANY HAS APPROVED THE MERGER
     AGREEMENT AND HAS DETERMINED THAT THE OFFER AND THE MERGER ARE FAIR TO AND
     IN THE BEST INTERESTS OF THE STOCKHOLDERS OF THE COMPANY AND RECOMMENDS
     THAT ALL OF THE STOCKHOLDERS OF THE COMPANY ACCEPT THE OFFER, TENDER THEIR
     SHARES AND APPROVE THE MERGER AGREEMENT AND THE MERGER, IF REQUIRED BY LAW.

          3. The Offer is being made for all outstanding Shares.


<PAGE>


          4. The Offer is being made pursuant to an Agreement and Plan of Merger
     dated as of May 27, 1999 (the 'Merger Agreement'), among Parent, the
     Purchaser, and the Company. The Merger Agreement provides that the
     Purchaser will be merged (the 'Merger') with and into the Company after the
     completion of the Offer and the satisfaction of certain conditions. As a
     result of the Merger, each Share issued and outstanding immediately prior
     to the Effective Time (as defined in the Merger Agreement) (other than
     Shares then owned by the Company, Parent, any direct or indirect subsidiary
     of Parent or by the stockholders of the Company, if any, who dissent from
     the Merger and comply with all of the provisions of the Massachusetts
     Business Corporation Act concerning the right, if applicable, of holders of
     Shares to seek appraisal of their Shares) will be converted into the right
     to receive the price paid in the Offer in cash, without interest.

          5. The Offer is conditioned upon, among other things, there being
     validly tendered and not withdrawn on or prior to the Expiration Date that
     number of outstanding Shares which, together with the outstanding Shares
     subject to the Stockholder Agreement that shall not have been so tendered,
     would represent at least two-thirds of all outstanding Shares on a fully
     diluted basis (as defined in the Offer to Purchase).

          6. The Offer and withdrawal rights will expire at 12:00 Midnight, New
     York City time, on Tuesday, June 29, 1999, unless the Offer is extended by
     the Purchaser. In all cases, payment for Shares purchased pursuant to the
     Offer will be made only after timely receipt by the Depositary of (a)
     certificates for such Shares (or a Book-Entry Confirmation) pursuant to the
     procedures set forth in Section 2 of the Offer to Purchase, (b) a Letter of
     Transmittal (or a facsimile copy thereof), properly completed and duly
     executed, or an 'Agent's Message' (as defined in Section 2 of the Offer to
     Purchase) and (c) any other documents required by the Letter of
     Transmittal.

          7. The Purchaser will pay any stock transfer taxes with respect to the
     transfer and sale of Shares to it or its order pursuant to the Offer,
     except as otherwise provided in Instruction 6 of the Letter of Transmittal.

     If you wish to have us tender any of or all your Shares, please so instruct
us by completing, executing and returning to us the instruction form set forth
below. An envelope to return your instructions to us is enclosed. If you
authorize the tender of your Shares, all such Shares will be tendered unless
otherwise specified below. YOUR INSTRUCTIONS TO US SHOULD BE FORWARDED PROMPTLY
TO PERMIT US TO SUBMIT A TENDER ON YOUR BEHALF PRIOR TO THE EXPIRATION OF THE
OFFER.

     The Offer is made solely by the Offer to Purchase and the related Letter of
Transmittal. The Offer is not being made to, nor will tenders be accepted from
or on behalf of, holders of Shares in any jurisdiction in which the making of
the Offer or the acceptance thereof would not be in compliance with the laws of
such jurisdiction. If the securities laws of any jurisdiction require the Offer
to be made by a licensed broker or dealer, the Offer shall be deemed to be made
on behalf of the Purchaser by Vector Securities International, Inc., the Dealer
Manager, or one or more registered brokers or dealers licensed under the laws of
such jurisdiction.

                    [The Next Page is the Instruction Form]


<PAGE>


                                INSTRUCTION FORM

             INSTRUCTIONS WITH RESPECT TO THE OFFER TO PURCHASE ALL
              OUTSTANDING SHARES OF COMMON STOCK OF ENDOGEN, INC.

     The undersigned acknowledges receipt of your letter enclosing the Offer to
Purchase dated June 2, 1999, of EWOK Acquisition Corp., a Massachusetts
corporation and a wholly owned subsidiary of PerBio Science AB, a Swedish
corporation, and the related Letter of Transmittal, relating to shares of
Common Stock, $.01 par value (the 'Shares'), of Endogen, Inc., a Massachusetts
corporation.

     This will instruct you to tender the number of Shares indicated below (or
if no number is indicated below, all Shares) held by you for the account of the
undersigned on the terms and conditions set forth in such Offer to Purchase and
the related Letter of Transmittal.

   PLEASE CHECK ONE OF THE TWO BOXES BELOW:

   [ ] Please tender Shares held by you for my account. I have identified in
   the box below the number of Shares to be tendered if I wish to tender less
   than all my Shares. Unless a number is provided in the box below, your
   signature(s) hereon shall constitute an instruction to us to tender all of
   your outstanding Shares.

   [ ] Please do not tender any Shares held by you for my account.

   Number of Shares to be Tendered (FILL IN ONLY IF LESS THAN ALL OF YOUR
   SHARES ARE BEING TENDERED -- DO NOT FILL IN IF YOU ARE TENDERING ALL OF
   YOUR SHARES PURSUANT TO YOUR ELECTION ABOVE): .......................... .

   SIGN HERE

   Signature(s)..............................................................

   (Print Name(s))...........................................................

   ..........................................................................

   (Print Address(es)) ......................................................

   ..........................................................................

   (Area Code and Telephone Number(s)).......................................

   (Taxpayer Identification or Social Security Number(s))....................






<PAGE>
            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9

GUIDELINES FOR DETERMINING THE PROPER IDENTIFICATION NUMBER TO GIVE THE
PAYER. -- Social Security numbers have nine digits separated by two hyphens:
i.e. 000-00-0000. Employer identification numbers have nine digits separated by
only one hyphen: i.e. 00-0000000. The table below will help determine the number
to give the payer. Identify the type of account held by you on the left and
provide the corresponding identification number described on the right.

<TABLE>
<S>                                <C>
                                   Give the
                                   SOCIAL
For this type of account:          SECURITY
                                   number of the
                                   person listed below

1. An individual's account         The individual

2. Two or more individuals (joint  The actual owner of the
   account)                        account, or if combined
                                   funds,
                                   any one of the
                                   individuals(1)

3. Husband and wife (joint         The actual owner of the
   account)                        account, or if joint
                                   funds, either
                                   person(1)

4. Custodian account of a minor    The minor(2)
   (Uniform Gift to Minors Act)

5. Adult and minor (joint          The adult, or if the
   account)                        minor is the only
                                   contributor, the
                                   minor(1)

6. Account in the name of          The ward, minor, or
   guardian or committee for a     incompetent
   designated ward, minor, or      person(3)
   incompetent person

7 a. The usual revocable savings   The grantor- trustee(1)
     trust account (grantor is
     also a trustee)
  b. So-called trust account that  The actual owner(1)
     is not a legal or valid
     trust under State law

8. Sole proprietorship account     The owner(4)
</TABLE>

<TABLE>
<S>                                <C>
                                   Give the EMPLOYER
For this type of account:          IDENTIFICATION
                                   number of the person
                                   listed below

 9. A valid trust, estate, or      The legal entity (do not
    pension trust                  furnish the identifying
                                   number of the personal
                                   representative or
                                   trustee unless the legal
                                   entity itself is not
                                   designated in the
                                   account title)(5)

10. Corporate account              The corporation

11. Religious, charitable, or      The organization
    educational organization
    account

12. Partnership account held in    The partnership
    the name of the business

13. Association, club, or other    The organization
    tax-exempt organization

14. A broker or registered         The broker or nominee
    nominee

15. Account with the Department    The public entity
    of Agriculture in the name of
    a public entity (such as a
    state or local government,
    school district, or prison)
    that receives agricultural
    program payments
</TABLE>

(1) List first and circle the name of the person whose number you furnish.
(2) Circle the minor's name and furnish the minor's social security number.
(3) Circle the ward's, minor's or incompetent person's name and furnish such
    person's social security number.
(4) Show the name of the owner.
(5) List first and circle the name of the legal trust, estate, or pension trust.
NOTE: If no name is circled when there is more than one name, the number will be
considered to be that of the first name listed.



<PAGE>


            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9

                                     PAGE 2

OBTAINING A NUMBER

If you don't have a taxpayer identification number or you don't know your
number, obtain Form SS-5, Application for a Social Security Number Card, or Form
SS-4, Application for Employer Identification Number, at the local office of the
Social Security Administration or the Internal Revenue Service and apply for a
number.

PAYEES EXEMPT FROM BACKUP WITHHOLDING
Payees specifically exempted from backup withholding on ALL payments include the
following:
   A corporation.
   A financial institution.
   An organization exempt from tax under section 501(a), or an individual
   retirement plan.
   The United States or any agency or instrumentality thereof.
   A State, the District of Columbia, a possession of the United States, or any
   subdivision or instrumentality thereof.
   A foreign government, a political subdivision of a foreign government, or any
   agency or instrumentality thereof.
   An international organization or any agency, or instrumentality thereof.
   A registered dealer in securities or commodities registered in the U.S. or a
   possession of the U.S.
   A real estate investment trust.
   A common trust fund operated by a bank under section 584(a).
   An exempt charitable remainder trust, or a non-exempt trust described in
   section 4947(a)(1).
   An entity registered at all times under the Investment Company Act of 1940.
   A foreign central bank of issue.
Payments of dividends and patronage dividends not generally subject to backup
withholding include the following:
   Payments to nonresident aliens subject to withholding under section 1441.
   Payments to partnerships not engaged in a trade or business in the U.S. and
   which have at least one nonresident partner.
   Payments of patronage dividends where the amount received is not paid in
   money.
   Payments made by certain foreign organizations.
   Payments made to a nominee.
Payments of interest not generally subject to backup withholding include the
following:
   Payments of interest on obligations issued by individuals. Note: You may be
   subject to backup withholding if this interest is $600 or more and is paid in
   the course of the payer's trade or business and you have not provided your
   correct taxpayer identification number to the payer.
   Payments of tax-exempt interest (including exempt-interest dividends under
   section 852).
   Payments described in section 6049(b)(5) to non-resident aliens.
   Payments on tax-free covenant bonds under section 1451.
   Payments made by certain foreign organizations.
   Payments made to a nominee.

EXEMPT PAYEES DESCRIBED ABOVE SHOULD FILE FORM W-9 TO AVOID POSSIBLE ERRONEOUS
BACKUP WITHHOLDING. FILE THIS FORM WITH THE PAYER, FURNISH YOUR TAXPAYER
IDENTIFICATION NUMBER, WRITE 'EXEMPT' ON THE FACE OF THE FORM, AND RETURN IT TO
THE PAYER. IF THE PAYMENTS ARE INTEREST, DIVIDENDS, OR PATRONAGE DIVIDENDS,
ALSO SIGN AND DATE THE FORM.

Certain payments other than interest, dividends, and patronage dividends, that
are not subject to information reporting are also not subject to backup
withholding. For details, see the regulations under sections 6041, 6041A(a),
6045, and 6050A.

PRIVACY ACT NOTICE. Section 6109 requires most recipients of dividend, interest,
or other payments to give taxpayer identification numbers to payers who must
report the payments to IRS. IRS uses the numbers for identification purposes.
Payers must be given the numbers whether or not recipients are required to file
tax returns. Beginning January 1, 1993, payers must generally withhold 31% of
taxable interest, dividend, and certain other payments to a payee who does not
furnish a taxpayer identification number to a payer. Certain penalties may also
apply.

PENALTIES
(1) PENALTY FOR FAILURE TO FURNISH TAXPAYER IDENTIFICATION NUMBER. If you fail
to furnish your taxpayer identification number to a payer, you are subject to a
penalty of $50 for each such failure unless your failure is due to reasonable
cause and not to willful neglect.
(2) FAILURE TO REPORT CERTAIN DIVIDEND AND INTEREST PAYMENTS. If you fail to
include any portion of an includible payment for interest, dividends, or
patronage dividends in gross income, such failure will be treated as being due
to negligence and will be subject to a penalty of 5% on any portion of an
under-payment attributable to that failure unless there is clear and convincing
evidence to the contrary.
(3) CIVIL PENALTY FOR FALSE INFORMATION WITH RESPECT TO WITHHOLDING. If you make
a false statement with no reasonable basis which results in no imposition of
backup withholding, you are subject to a penalty of $500.
(4) CRIMINAL PENALTY FOR FALSIFYING INFORMATION. Falsifying certifications or
affirmations may subject you to criminal penalties including fines and/or
imprisonment.

FOR ADDITIONAL INFORMATION CONTACT YOUR TAX CONSULTANT OR THE INTERNAL REVENUE
SERVICE.











<PAGE>


THIS ANNOUNCEMENT IS NEITHER AN OFFER TO PURCHASE NOR A SOLICITATION OF AN OFFER
TO SELL SHARES. THE OFFER IS MADE SOLELY BY THE OFFER TO PURCHASE DATED JUNE 2,
1999, AND THE RELATED LETTER OF TRANSMITTAL AND IS NOT BEING MADE TO, AND
TENDERS WILL NOT BE ACCEPTED FROM OR ON BEHALF OF, HOLDERS OF SHARES IN ANY
JURISDICTION IN WHICH THE MAKING OF THE OFFER OR THE ACCEPTANCE THEREOF WOULD
NOT BE IN COMPLIANCE WITH THE LAWS OF SUCH JURISDICTION. IF THE SECURITIES LAWS
OF ANY JURISDICTION REQUIRE THE OFFER TO BE MADE BY A LICENSED BROKER OR DEALER,
THE OFFER SHALL BE DEEMED TO BE MADE ON BEHALF OF EWOK ACQUISITION CORP. BY
VECTOR SECURITIES INTERNATIONAL, INC., OR ONE OR MORE REGISTERED BROKERS OR
DEALERS LICENSED UNDER THE LAWS OF SUCH JURISDICTION.

                          NOTICE OF OFFER TO PURCHASE
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                                 ENDOGEN, INC.
                                       AT
                          $3.75 NET PER SHARE IN CASH
                                       BY
                             EWOK ACQUISITION CORP.
                           A WHOLLY OWNED SUBSIDIARY
                                       OF
                               PERBIO SCIENCE AB

     EWOK Acquisition Corp., a Massachusetts corporation (the 'Purchaser') and a
wholly owned subsidiary of PerBio Science AB, a Swedish corporation ('Parent'),
is offering to purchase all outstanding shares of Common Stock, $.01 par value
(the 'Shares'), of Endogen, Inc., a Massachusetts corporation (the 'Company'),
at a purchase price of $3.75 per Share, net to the seller in cash, upon the
terms and subject to the conditions set forth in the Offer to Purchase dated
June 2, 1999, and the related Letter of Transmittal (which together constitute
the 'Offer'). See the Offer to Purchase for capitalized terms used but not
defined herein.

         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
             NEW YORK CITY TIME, ON TUESDAY, JUNE 29, 1999, UNLESS
                             THE OFFER IS EXTENDED.

     THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN ON OR PRIOR TO THE EXPIRATION DATE (AS DEFINED BELOW)
THAT NUMBER OF OUTSTANDING SHARES WHICH, TOGETHER WITH THE OUTSTANDING SHARES
SUBJECT TO THE STOCKHOLDER AGREEMENT (AS DEFINED BELOW) THAT SHALL NOT HAVE BEEN
SO TENDERED, WOULD REPRESENT AT LEAST TWO-THIRDS OF ALL OUTSTANDING SHARES ON A
FULLY DILUTED BASIS (AS DEFINED BELOW). THE PURCHASER RESERVES THE RIGHT
(SUBJECT TO OBTAINING THE EXPRESS WRITTEN CONSENT OF THE COMPANY AND THE
APPLICABLE RULES AND REGULATIONS OF THE SECURITIES AND EXCHANGE COMMISSION (THE
'COMMISSION')), WHICH IT PRESENTLY HAS NO INTENTION OF EXERCISING, TO WAIVE OR
REDUCE THE MINIMUM CONDITION.

     THE OFFER IS NOT CONDITIONED ON OBTAINING FINANCING.

     THE BOARD OF DIRECTORS OF THE COMPANY HAS APPROVED THE MERGER AGREEMENT AND
HAS DETERMINED THAT THE OFFER AND THE MERGER ARE FAIR TO AND IN THE BEST
INTERESTS OF THE STOCKHOLDERS OF THE COMPANY AND RECOMMENDS THAT ALL OF THE
STOCKHOLDERS OF THE COMPANY ACCEPT THE OFFER, TENDER THEIR SHARES AND APPROVE
THE MERGER AGREEMENT AND THE MERGER, IF REQUIRED BY LAW.





<PAGE>


     The Offer is being made pursuant to an Agreement and Plan of Merger dated
as of May 27, 1999 (the 'Merger Agreement'), among Parent, the Purchaser and the
Company. The Merger Agreement provides that the Purchaser will be merged (the
'Merger') with and into the Company after the completion of the Offer and the
satisfaction of certain conditions. As a result of the Merger, each Share issued
and outstanding immediately prior to the Effective Time (as defined in the
Merger Agreement) (other than Shares then owned by the Company, Parent, any
subsidiary of Parent or by stockholders of the Company, if any, who dissent from
the Merger and comply with all of the provisions of the Massachusetts Business
Corporation Law concerning the right, if applicable, of holders of Shares to
seek appraisal of their Shares) will be converted into the right to receive the
price paid in the Offer in cash, without interest.

     In connection with the execution of the Merger Agreement, the Purchaser and
Parent entered into a Stockholder Agreement, dated as of May 27, 1999 (the
'Stockholder Agreement'), with Owen A. Dempsey, the President and Chief
Executive Officer of the Company, Hayden H. Harris, Chairman of the Board,
Charles R. Burke, Christine A. Burns, Avery W. Catlin, Wallace G. Dempsey, Irwin
J. Gruverman, G&G Diagnostics Limited Partnership I, Hayden H. Harris Living
Trust DTD 3/6/98 and Wolfgang Woloszczuk (collectively, the 'Selling
Stockholders'), pursuant to which such Selling Stockholders have agreed to
tender to the Purchaser, and the Purchaser has agreed to purchase, all Shares
beneficially owned by them, including 569,600 Shares currently outstanding which
represent approximately sixteen percent (16%) of the Shares issued and
outstanding, plus Shares subsequently acquired by a Selling Stockholder through
the exercise of options or otherwise, at a price per Share equal to the price
paid in the Offer, provided that such obligation to tender and such obligation
to purchase are subject to certain conditions, including the Minimum Condition
having been satisfied and the Purchaser having accepted Shares for payment under
the Offer. Pursuant to the Stockholder Agreement, each Selling Stockholder has
also executed and delivered a proxy for the benefit of the Purchaser with
respect to the Shares subject to the Stockholder Agreement owned by such Selling
Stockholder to vote such Shares against certain competing transactions, as set
forth in Section 12 of the Offer to Purchase.

     Pursuant to the Merger Agreement, the Company has granted the Purchaser an
irrevocable option (the 'Purchaser Stock Option') to purchase up to 690,172
Shares, which represents approximately 19.9% of the Company's outstanding Common
Stock at a price per share equal to the Offer price payable in cash. The
Purchaser Stock Option may be exercised, in whole or in part, at any time and
from time to time after the date on which the Purchaser has accepted for payment
the Shares tendered pursuant to the Offer and subject to satisfaction of the
Minimum Condition if, but only if, Parent and Purchaser agree to permanently
waive the offer conditions set forth in the Merger Agreement.

     For purposes of the Offer, the Purchaser will be deemed to have accepted
for payment (and thereby purchased) Shares validly tendered to the Purchaser on
or prior to the Expiration Date and not properly withdrawn if, as and when the
Purchaser gives oral or written notice to the Depositary of the Purchaser's
acceptance for payment of such Shares pursuant to the Offer. Upon the terms and
subject to the conditions of the Offer, payment for Shares purchased pursuant to
the Offer will be made by deposit of the purchase price with the Depositary,
which will act as agent for tendering stockholders for the purpose of receiving
payments from the Purchaser and transmitting payments to tendering stockholders.
Under no circumstances will interest on the purchase price of the Shares be paid
by the Purchaser by reason of any delay in making such payment. In all cases,
payment for Shares purchased pursuant to the Offer will be made only after
timely receipt by the Depositary of (a) certificates for such Shares (or a Book
Entry Confirmation) pursuant to the procedures set forth in Section 2 of the
Offer to Purchase, (b) a Letter of Transmittal (or a facsimile copy thereof),
properly completed and duly executed, or an 'Agent's Message' and (c) any other
documents required by the Letter of Transmittal.

     The term 'Expiration Date' means 12:00 Midnight, New York City time, on
Tuesday, June 29, 1999, unless and until the Purchaser, in its sole discretion,
shall have extended the period of time for which the Offer is open, in which
event the term 'Expiration Date' shall mean the latest time and date at which
the Offer, as so extended by the Purchaser, shall expire.

     The term 'fully diluted basis' excludes the following: (a) all outstanding
stock options issued pursuant to the Company's 1992 Stock Plan that are
irrevocably terminated, consistent with Section

                                       2





<PAGE>


7.4(a)(A)(i) or (B) of the Merger Agreement, effective as of the time that the
Purchaser accepts for payment, and pays for, all Shares tendered and not
withdrawn pursuant to the Offer; (b) all outstanding options issued pursuant to
the Company's 1993 Non-Employee Director Stock Option Plan that are irrevocably
terminated by the holders of those options, effective as of the time that the
Purchaser accepts for payment, and pays for, all Shares tendered, and not
withdrawn pursuant to the Offer; and (c) a certain warrant to purchase 125,000
shares of common stock of the Company held by Third Wave Technologies, Inc.;
provided that such warrant is irrevocably terminated by the holder thereof,
effective as of the time that the Purchaser accepts for payment, and pays for,
all Shares tendered and not withdrawn pursuant to the Offer.

     The Merger Agreement provides that the Purchaser may extend the Offer by
giving oral or written notice of such extension to the Depositary, without the
consent of the Company, only (1) if at the Expiration Date any of the conditions
to the Purchaser's obligations to accept Shares for payment are not satisfied or
waived, until such time as such conditions are satisfied or waived (each
individual extension not to exceed five (5) business days after the previously
scheduled Expiration Date), (2) for any period required by any rule, regulation,
interpretation or position of the Commission or the staff thereof applicable to
the Offer, and (3) on up to two occasions in each case for period of not more
than five (5) business days beyond the latest Expiration Date if on such
Expiration Date there shall have been tendered more than the number of Shares
sufficient to satisfy the Minimum Condition but less than 90% of the Shares. In
addition, the Purchaser has agreed in the Merger Agreement that it will not,
without the express written consent of the Company and after giving oral or
written notice of such extension to the Depositary, (1) reduce the number of
Shares subject to the Offer, (2) reduce the Offer price, (3) add to or modify
the conditions set forth in Section 14 of the Offer to Purchase, including the
Minimum Condition, (4) except as provided above, extend the Offer if all of the
conditions set forth in Section 14 of the Offer to Purchase are satisfied or
waived, (5) change the form of the consideration payable in the Offer or (6)
amend or alter any term of the Offer in any manner materially adverse to the
Company's stockholders; provided, however, that nothing contained in the Merger
Agreement will prohibit the Purchaser, in its sole discretion without the
consent of the Company, from waiving satisfaction of any condition of the Offer
other than the Minimum Condition. The Purchaser shall not have any obligation
to pay interest on the purchase price for tendered Shares, whether or not the
Purchaser exercises its right to extend the Offer.

     There can be no assurance that the Purchaser will exercise its right to
extend the Offer (other than as required by the Merger Agreement or applicable
law). Any extension, amendment or termination of the Offer, or the waiver of any
condition of the Offer, will be followed as promptly as practicable by a public
announcement.

     If any tendered Shares are not purchased pursuant to the Offer for any
reason, or if certificates are submitted which represent more Shares than are
tendered, certificates for such Shares not purchased or tendered will be
returned (or, in the case of Shares delivered by book-entry transfer within DTC
pursuant to the procedures set forth in Section 2 of the Offer to Purchase, such
Shares will be credited to an account maintained within DTC without expense to
the tendering stockholder) as promptly as practicable following the expiration,
termination or withdrawal of the Offer. Certificates representing Shares
canceled in the Merger will not be returned.

     Except as otherwise provided below, tenders of Shares are irrevocable.
Shares tendered pursuant to the Offer may be withdrawn on, or at any time prior
to, the Expiration Date and, unless theretofore accepted for payment as provided
in the Offer to Purchase, may also be withdrawn on or after August 1, 1999.

     For a withdrawal to be effective, a written, telegraphic or facsimile
transmission notice of withdrawal must be timely received by the Depositary at
one of its addresses set forth on the back cover of the Offer to Purchase and
must specify the name of the person who tendered the Shares to be withdrawn, the
number of Shares to be withdrawn and the name of the registered holder, if
different from that of the person who tendered such Shares. If certificates for
Shares have been delivered or otherwise identified to the Depositary, then,
prior to the physical release of such certificates, the serial numbers shown on
the particular certificates evidencing the Shares to be withdrawn and a signed
notice of withdrawal with signatures guaranteed by an Eligible Institution,
except in the case of Shares tendered by an Eligible Institution, must also be
furnished to the Depositary as aforesaid. If Shares have been delivered pursuant
to the procedure for book-entry transfer as set forth in Section 2 of the Offer
to Purchase, any notice of withdrawal must also specify the name and number of
the account at DTC to be credited with the withdrawn Shares and otherwise comply
with DTC's procedures.

     The information required to be disclosed by Rule 14d-6(e)(1)(vii) of the
General Rules and Regulations under the Exchange Act is contained in the Offer
to Purchase and is incorporated herein by reference.

     STOCKHOLDERS ARE URGED TO READ THE OFFER TO PURCHASE AND THE RELATED LETTER
OF TRANSMITTAL CAREFULLY BEFORE DECIDING WHETHER TO TENDER THEIR SHARES PURSUANT
TO THE OFFER.

     Questions and requests for assistance or for copies of the Offer to
Purchase, the Letter of Transmittal, the Notice of Guaranteed Delivery or other
related materials may be directed to the

                                       3





<PAGE>


Information Agent or the Dealer Manager at their respective addresses and
telephone numbers set forth below. Holders of Shares may also contact brokers,
dealers, commercial banks and trust companies for additional copies of the Offer
to Purchase, the Letter of Transmittal, the Notice of Guaranteed Delivery or
other related materials.

                      The Information Agent for the Offer is:

                         [Georgeson & Company Inc. Logo]

                               Wall Street Plaza
                               New York, NY 10005
                            (212) 440-9800 (Collect)
                        or Call Toll Free (800) 223-2064

                        The Dealer Manager for the Offer is:

                        VECTOR SECURITIES INTERNATIONAL, INC.
                              1751 Lake Cook Road
                                   Suite 350
                              Deerfield, IL 60015
                            (847) 374-3853 (collect)

June 2, 1999











<PAGE>

CONTACTS FOR ENDOGEN:
Owen A. Dempsey, President & CEO                    Michelle L. Linn
Avery W. Catlin, VP Finance & CFO                   or Karen C.K. Drake
(781) 937-0890                                      Feinstein Kean Partners Inc.
website: http://www.endogen.com                     (617) 577-8110
                                                    website: http://www.fkpi.com

CONTACT FOR PIERCE CHEMICAL COMPANY:
Robb Anderson, President
(815) 968-0747

                                                          FOR IMMEDIATE RELEASE

                PERSTORP AB MAKES OFFER TO ACQUIRE ENDOGEN, INC.

ROCKFORD, ILLINOIS AND WOBURN, MASSACHUSETTS, MAY 27, 1999 - Perstorp AB
subsidiary PerBio Science AB and Endogen, Inc. (Nasdaq: ENDG; BSE: EDG)
announced today that they have executed a definitive merger agreement that
provides for a cash tender offer for all of the outstanding shares of Endogen,
Inc. for a total transaction value of approximately $13.6 million. PerBio
Science AB, which is a leading supplier in several life-science product
segments, consists of the American companies Pierce Chemical Company of
Rockford, Illinois and HyClone Laboratories, Inc. of Logan, Utah and of the
Sweden-based company Atos Medical.

PerBio Science's offer relates to the acquisition of all of the outstanding
shares of Endogen, Inc. for $3.75 per share in cash. The tender offer will be
commenced within five business days. The tender offer will be conditional upon,
among other things, there being validly tendered and not withdrawn at least
two-thirds of the fully-diluted outstanding shares of Endogen, Inc. Upon the
successful completion of the tender offer, a subsidiary of PerBio Science AB
will be merged into Endogen, Inc. and any Endogen, Inc. shares not tendered and
purchased in the tender offer will be converted into the right to receive $3.75
per share in cash.

In connection with the execution of the merger agreement, PerBio Science AB has
entered into an agreement with directors and executive officers of Endogen, Inc.
whereby they have agreed to tender their outstanding shares in the tender offer.

As part of PerBio Science AB, Endogen, Inc. will be closely affiliated with
Pierce Chemical Company. Mr. Robb Anderson, President of Pierce Chemical
Company, said today, "The merger with Endogen, Inc. will strengthen PerBio
Science's position as a world leader providing biotechnology products for the
rapidly growing life science research and drug discovery markets. Endogen's
product portfolio adds to our existing product lines and will enable PerBio
Science to expand it's offerings of high-tech products for immunologists,
molecular biologists and cell biologist."








<PAGE>




PerBio Science AB (the former Perstorp Life Science Division) is a wholly owned
subsidiary of Perstorp AB, a global chemistry and materials technology
corporation located in Perstorp, Sweden. In October 1999, PerBio Science AB is
to be spun off to shareholders and listed on the Stockholm Exchange.

Endogen, Inc. is a supplier of specialty reagents, immunoassay test kits and
molecular research products to customers involved in biomedical research, the
biotechnology industry and pharmaceutical drug discovery.



                                      # # #

















<PAGE>



Perstorp Group - Perstorp AB Makes Offer                           Page 1 of 2

PERSTORP AB MAKES OFFER
FOR AMERICAN BIOTECHNOLOGY COMPANY

Perstorp AB subsidiary PerBio Science AB today executed a definitive agreement
that provides for cash tender offer for all of the outstanding shares of Endogen
Inc., an American biotechnology company. Endogen, which is listed on Nasdaq
SmallCap in New York and the Boston Stock Exchange, has annual sales of
approximately USD 10 million (approx. SEK 85 million).

PerBio Science AB is a wholly owned subsidiary of Perstorp AB, which is to be
spun off to shareholders of Perstorp and listed on the Stockholm Stock Exchange
in October 1999.

PerBio Science's offer relates to the acquisition of all of the shares
outstanding in Endogen for USD 3.75 per share. The total purchase price will be
approximately USD 13.6 million (approx. SEK 115 million), including stock
options and warrants.The tender offer is subject to customary conditions, and
that there being validly tendered and not withdrawn at least two-thirds of the
Endogen shares outstanding. The tender offer will be commenced within five
business days in the United States. Upon the successful completion of the tender
offer, a subsidiary of PerBio Science AB will be merged into Endogen Inc. and
any Endogen Inc. shares not tendered and purchased in the tender offer will be
converted into the right to receive USD 3.75 per share in cash.

PerBio Science has reached agreements with several senior executives in Endogen
regarding continued employment. In addition, an agreement have been reached with
several senior executives and directors, whereby they will tender all of their
outstanding shares of stock in the tender offer.

Endogen Inc develops, manufactures and supplies biomedical research products
used in basic research and drug discovery. Leading medical research centers,
universities, pharmaceutical companies and biotech firms worldwide use Endogen
products in the study of diseases such as cancer, autoimmune disorders and AIDS.
The company's expertise, mainly in the monoclonal antibody and recombinant DNA
technology, will strengthen PerBio Science's know-how in the biotechnology
field.

PerBio Science is active in the expansive biotechnology sector and combines
favorable profitability with high growth. PerBio Science had net sales of SEK
706 million (1997: 549) in the 1998 calendar year and SEK 248 million during the
first quarter of 1999, including sales by the plant acquired from Amersham
Pharmacia Biotech at the end of 1998.

The acquisition will have only a minor impact on Perstorp AB's income statement
and balance sheet. Prior to the spin-off of its shares to Perstorp AB
shareholders, PerBio Science has been provided with shareholders' equity that
permits the acquisition of operations with the potential to strengthen the
company's business and technology base.

- --------------
for further information please contact:







<PAGE>



Perstorp Group - Perstorp AB Makes Offer                           Page 2 of 2


Rolf Rahmberg, Vice President, Corporate Communications,
Perstorp AB, tel + 46 435 381 59












<PAGE>

================================================================================



                          AGREEMENT AND PLAN OF MERGER


                                      AMONG


                                PERBIO SCIENCE AB

                             EWOK ACQUISITION CORP.


                                       AND


                                  ENDOGEN, INC.


                            DATED AS OF MAY 27, 1999


================================================================================






<PAGE>


                             Index of Defined Terms

                             ----------------------

<TABLE>
<S>                                                                                  <C>
Affiliate.............................................................................4.6(b)
Agreement...........................................................................Preamble
Alternative Transaction...............................................................6.2(a)
Acquisition Agreement.................................................................6.2(b)
Articles of Organization..............................................................2.5(a)
Benefit Plans........................................................................4.15(a)
By-laws...............................................................................2.5(b)
Certificate of Merger....................................................................2.3
Certificates..........................................................................3.2(b)
Closing..................................................................................2.2
Closing Date.............................................................................2.2
Code.................................................................................4.15(a)
Commitments.............................................................................4.10
Commonly Controlled Entity...........................................................4.15(a)
Company.............................................................................Preamble
Company Common Stock................................................................Recitals
Company Intellectual Property...........................................................4.19
Company Preferred Stock..................................................................4.2
Company Stock Option..................................................................7.4(a)
Company Stockholder Approval.............................................................4.4
Confidentiality Agreement................................................................7.2
Dissenting Shares.....................................................................3.1(d)
Dissenting Stockholder................................................................3.1(d)
Effective Time...........................................................................2.3
Employee Stock Purchase Plan..........................................................7.4(b)
Employment Agreements...............................................................Recitals
Environmental Laws...................................................................4.12(a)
ERISA................................................................................4.15(a)
Exchange Act..........................................................................1.1(b)
Expenses..............................................................................7.7(b)
Expiration Date.......................................................................1.1(a)
Filed SEC Documents......................................................................4.8
Governmental Entity......................................................................4.5
Hazardous Materials..................................................................4.12(b)
Indebtedness..........................................................................4.6(c)
Information Statement....................................................................4.7
Intellectual Property ..................................................................4.19
Knowledge...............................................................................10.3
Liens.................................................................................4.3(a)
made available..........................................................................10.3
material adverse affect.................................................................10.3

</TABLE>










<PAGE>


<TABLE>
<S>                                                                                  <C>
material adverse change................................................................10.3
MBCL.....................................................................................2.1
Merger..............................................................................Recitals
Merger Consideration..................................................................3.1(c)
Minimum Condition..................................................................Exhibit A
Net Amount............................................................................7.4(a)
Offer...............................................................................Recitals
Offer Conditions......................................................................1.1(a)
Offer Documents.......................................................................1.1(b)
Offer Price.........................................................................Recitals
Option Notice...........................................................................7.10
Parachute Gross-Up Payment..............................................................4.17
Parent..............................................................................Preamble
Paying Agent..........................................................................3.2(a)
PCBs.................................................................................4.12(b)
Pension Plans........................................................................4.15(a)
Permits.................................................................................4.11
Person..................................................................................10.3
Plan.....................................................................................6.7
Post-Signing Returns.....................................................................6.3
Proxy Statement..........................................................................4.5
Release..............................................................................4.12(b)
Schedule 14D-1........................................................................1.1(b)
Schedule 14D-9........................................................................1.2(b)
SEC...................................................................................1.1(a)
SEC Documents.........................................................................4.6(a)
Securities Act........................................................................4.6(a)
Shares..............................................................................Recitals
Stock Option Plans....................................................................7.4(a)
Stockholder Agreement...............................................................Recitals
Stockholders Meeting..................................................................7.1(a)
Sub.................................................................................Preamble
Sub Shares..............................................................................7.10
Sub Stock Option........................................................................7.10
Subsidiaries..........................................................................4.3(a)
Subsidiary..............................................................................10.3
Superior Proposal.....................................................................9.1(d)
Surviving Corporation....................................................................2.1
Taxes...................................................................................4.16
Third Party Proposal..................................................................6.2(a)
Warrant...............................................................................7.4(a)

</TABLE>







<PAGE>





                          AGREEMENT AND PLAN OF MERGER

        AGREEMENT AND PLAN OF MERGER, dated as of May 27, 1999 (this
"Agreement"), among PERBIO SCIENCE AB, a Swedish corporation ("Parent"), EWOK
ACQUISITION CORP., a Massachusetts corporation and a wholly owned subsidiary of
Parent ("Sub"), and ENDOGEN, INC., a Massachusetts corporation (the "Company").

        WHEREAS the respective Boards of Directors of Parent, Sub and the
Company have approved the acquisition of the Company by Parent on the terms and
subject to the conditions set forth in this Agreement and believe that the
Merger (as defined below), is advisable and in the best interests of their
respective Stockholders;

        WHEREAS, in furtherance of such acquisition, pursuant to this Agreement,
Parent has agreed to cause Sub to make a tender offer to purchase all the
outstanding shares of Common Stock, par value $.01 per share, of the Company
(the "Company Common Stock"; all the outstanding shares of Company Common Stock
being hereinafter collectively referred to as the "Shares") at a purchase price
of $3.75 per Share in U.S. dollars (the "Offer Price"), net to the seller in
cash, without interest thereon, upon the terms and subject to the conditions set
forth in this Agreement (as it may be amended from time to time as permitted
under this Agreement, the "Offer"); and the Board of Directors of the Company
has adopted resolutions approving the Offer and the Merger recommending that the
Company's stockholders accept the Offer and approving the acquisition of Shares
by Sub pursuant to the Offer and the Stockholder Agreement (as defined herein);

        WHEREAS the respective Boards of Directors of Parent, Sub and the
Company have each approved the merger of Sub into the Company (the "Merger"),
upon the terms and subject to the conditions set forth in this Agreement,
whereby each Share, other than Shares owned directly or indirectly by Parent or
the Company and Dissenting Shares (as defined in Section 3.1(d)), will be
converted into the right to receive the price per share paid in the Offer;

        WHEREAS, concurrently with the execution of this Agreement and as an
inducement to Parent to enter into this Agreement, Parent, Sub and certain
stockholders of the Company including all of the Company's executive officers
and directors are entering into a Stockholder Agreement (the "Stockholder
Agreement") pursuant to which such stockholders have, among other things, agreed
to sell or tender all of such stockholders' Shares to Sub at a cash price per
Share equal to the Offer Price, upon the terms and subject to the conditions set
forth in the Stockholder Agreement

        WHEREAS, concurrently with the execution of this Agreement and as an
inducement to Parent to enter into this Agreement, Sub and certain employees of
the Company are executing and delivering Employment Agreements (the "Employment
Agreements") copies of which have been delivered to the Company; and







<PAGE>


        WHEREAS Parent, Sub and the Company desire to make certain
representations, warranties, covenants and agreements in connection with the
Offer and the Merger and also to prescribe various conditions to the Offer and
the Merger.

        NOW, THEREFORE, in consideration of the foregoing and the mutual
covenants and agreements herein contained, and intending to be legally bound
hereby, Parent, Sub and the Company hereby agree as follows:

                                    ARTICLE I

                                    THE OFFER

1.1.    The Offer.

        (a) Subject to the terms and conditions set forth in this Agreement,
within five (5) business days after the date of the public announcement, which
shall occur on the date hereof or the following day, by Parent and the Company
of this Agreement, Sub shall, and Parent shall cause Sub to, commence (within
the meaning of Rule 14d-2 under the Exchange Act (as hereinafter defined)) the
Offer, which shall expire at midnight, New York City time, on the date that is
twenty (20) business days after the date the Offer is commenced (the initial
"Expiration Date," and any expiration time and date established pursuant to an
authorized extension of the Offer as so extended, also an "Expiration Date").
The obligation of Sub to, and of Parent to cause Sub to, commence the Offer,
conduct and consummate the Offer as soon as practicable after the date hereof
and accept for payment, and pay for, any Shares tendered and not withdrawn
pursuant to the Offer shall be subject only to the conditions set forth in
Exhibit A (the "Offer Conditions") (any of which may be waived in whole or in
part by Sub in its sole discretion, provided that, without the express written
consent of the Company, Sub may not waive the Minimum Condition (as defined in
Exhibit A)). Sub expressly reserves the right, subject to compliance with the
Exchange Act, to modify the terms of the Offer, except that, without the express
written consent of the Company, Sub shall not (i) reduce the number of Shares
subject to the Offer, (ii) reduce the Offer Price, (iii) add to or modify the
Offer Conditions, including the Minimum Condition, (iv) except as provided in
the next sentence, extend the Offer, if all of the Offer Conditions are
satisfied or waived, (v) change the form of consideration payable in the Offer
or (vi) amend or alter any term of the Offer in any manner materially adverse to
the holders of the Shares, provided, however, that nothing contained herein
shall prohibit Sub, in its sole discretion without the consent of the Company,
from waiving satisfaction of any condition to the Offer other than the Minimum
Condition. Notwithstanding the foregoing, Sub may, without the consent of the
Company, (A) extend the Offer (each individual extension not to exceed five (5)
business days after the previously scheduled Expiration Date), if at the then
scheduled Expiration Date of the Offer any of the Offer Conditions shall not be
satisfied or waived, until such time as such conditions are satisfied or waived,
(B) extend the Offer for any period required by any rule, regulation,
interpretation or position of the Securities and Exchange Commission (the "SEC")
or the staff thereof applicable to the Offer, and (C) extend the Offer on up to
two occasions in each case for period of not more than five (5) business days
beyond the latest Expiration Date if on





                                       2




<PAGE>



such Expiration Date there shall have been tendered more than the number of
Shares sufficient to satisfy the Minimum Condition but less than 90% of the
Shares; provided, Parent agrees to permanently waive the Offer Conditions.
Subject to the terms and conditions of the Offer and this Section 1.1(a), Sub
shall, and Parent shall cause Sub to, accept for payment, and pay for, all
Shares validly tendered and not withdrawn pursuant to the Offer that Sub becomes
obligated to accept for payment, and pay for, pursuant to the Offer as soon as
practicable after the expiration of the Offer.

        (b) On the date of commencement of the Offer, Parent and Sub shall file
with the SEC a Tender Offer Statement on Schedule 14D-1 (the "Schedule 14D-1")
with respect to the Offer, which shall contain an offer to purchase and a
related letter of transmittal (such Schedule 14D-1 and the documents included
therein pursuant to which the Offer will be made, together with any supplements
or amendments thereto, the "Offer Documents"). Parent and Sub agree that the
Offer Documents shall comply as to form in all material respects with the
Securities Exchange Act of 1934, as amended and the rules and regulations
promulgated thereunder (the "Exchange Act"), and the Offer Documents, on the
date first published, sent or given to the Company's stockholders, shall not
contain any untrue statement of a material fact or omit to state any material
fact required to be stated therein or necessary in order to make the statements
therein, in light of the circumstances under which they were made, not
misleading, except that no representation or warranty is made by Parent or Sub
with respect to written information supplied by or on behalf of the Company or
any of its stockholders for inclusion or incorporation by reference in the Offer
Documents. Parent, Sub and the Company each agrees promptly to correct any
written information provided by it for use in the Offer Documents if and to the
extent that such information shall have become false or misleading in any
material respect, and Parent and Sub further agree to take all steps necessary
to cause the Schedule 14D-1 as so corrected to be filed with the SEC and the
other Offer Documents as so corrected to be disseminated to holders of Shares,
in each case as and to the extent required by applicable laws. The Company and
its counsel shall be given reasonable opportunity to review and comment upon the
Offer Documents prior to their filing with the SEC or dissemination to the
stockholders of the Company. Parent and Sub agree to provide the Company and its
counsel any comments Parent, Sub or their counsel may receive from the SEC or
its staff with respect to the Offer Documents promptly after the receipt of such
comments.

        (c) Parent shall provide or cause to be provided to Sub on a timely
basis the funds sufficient to accept for payment, and pay for, any and all
Shares that Sub becomes obligated to accept for payment, and pay for, pursuant
to the Offer.

1.2.    Company Actions.

        (a) The Company hereby approves of and consents to the Offer and
represents that the Board of Directors of the Company, at a meeting duly called
and held, duly adopted resolutions approving this Agreement and the Stockholder
Agreement, the Offer and the Merger, determining that the terms of the Offer and
the Merger are fair to, and in the best interests of, the Company and its
stockholders and recommending that the Company's stockholders accept the Offer,
tender their Shares pursuant to the Offer and approve and adopt the Merger and
this





                                       3







<PAGE>

Agreement (if required); provided, however, that such recommendation and
approval may be withdrawn, modified or amended to the extent that the Board of
Directors of the Company determines in good faith, after consultation with its
outside legal counsel, that failure to take such action could reasonably be
expected to result in a breach of the Board of Directors' fiduciary obligations
under applicable law and the Company terminates this Agreement pursuant to
Section 9.1(d). The Company represents that its Board of Directors has received
the opinion of Adams, Harkness & Hill, Inc. ("AH&H") dated the date of this
Agreement to the effect that, as of such date and based upon and subject to the
matters set forth therein, the cash consideration to be received by the holders
of Shares (other than Parent and its Affiliates) pursuant to the Offer and the
Merger is fair from a financial point of view to such holders, and a complete
and correct signed copy of such opinion will promptly be delivered by the
Company to Parent. The Company has been authorized by AH&H to permit the
inclusion of such opinion (or a reference thereto) in the Schedule 14D-1, the
Schedule 14D-9 (as hereinafter defined) and the Proxy Statement (as hereinafter
defined).

        (b) On the date the Offer Documents are filed with the SEC, or promptly
thereafter, the Company shall file with the SEC a Solicitation/Recommendation
Statement on Schedule 14D-9 with respect to the Offer (such Schedule 14D-9, as
amended from time to time, the "Schedule 14D-9") containing the recommendation
described in paragraph (a) and shall mail the Schedule 14D-9 to the stockholders
of the Company to the extent required by Rule 14d-9 promulgated under the
Exchange Act and any other applicable federal securities laws; provided,
however, that if the Board of Directors of the Company determines in good faith,
after consultation with its outside legal counsel, that the amendment or
withdrawal of such recommendation is likely to be required in order for its
members to comply with their fiduciary duties under applicable law and the
Company terminates this Agreement pursuant to Section 9.1(d), then any such
amendment or withdrawal, and any related amendment of the Schedule 14D-9, shall
not constitute a breach of this Agreement. The Schedule 14D-9 shall comply as to
form in all material respects with the requirements of the Exchange Act and the
rules and regulations promulgated thereunder and, on the date filed with the SEC
and on the date first published, sent or given to the Company's stockholders,
shall not contain any untrue statement of a material fact or omit to state any
material fact required to be stated therein or necessary in order to make the
statements therein, in light of the circumstances under which they were made,
not misleading, except that no representation or warranty is made by the Company
with respect to written information supplied by or on behalf of Parent or Sub
for inclusion in the Schedule 14D-9. Each of the Company, Parent and Sub agrees
promptly to correct any written information provided by it for use in the
Schedule 14D-9 if and to the extent that such information shall have become
false or misleading in any material respect, and the Company further agrees to
take all steps necessary to amend or supplement the Schedule 14D-9 and to cause
the Schedule 14D-9 as so amended or supplemented to be filed with the SEC and
disseminated to the Company's stockholders, in each case as and to the extent
required by applicable laws. Parent and its counsel shall be given reasonable
opportunity to review and comment upon the Schedule 14D-9 prior to its filing
with the SEC or dissemination to stockholders of the Company. The Company agrees
to provide Parent and its counsel any comments the Company or its counsel may
receive from the SEC or its staff with respect to the Schedule 14D-9 promptly
after the receipt of such comments.




                                       4








<PAGE>

        (c) In connection with the Offer and the Merger, the Company shall cause
its transfer agent to furnish Sub promptly with mailing labels containing the
names and addresses of the record holders of Shares as of a recent date and of
those persons becoming record holders subsequent to such date, together with
copies of all lists of stockholders, security position listings and computer
files and all other information in the Company's possession or control regarding
the beneficial owners of Shares, and shall furnish to Sub such information and
assistance (including updated lists of stockholders, security position listings
and computer files) as Parent may reasonably request in communicating the Offer
to the Company's stockholders. Subject to the requirements of applicable law,
and except for such steps as are necessary to disseminate the Offer Documents
and any other documents necessary to consummate the Merger, Parent and Sub and
their agents shall hold in confidence the information contained in any such
labels, listings and files, will use such information only in connection with
the Offer and the Merger and, if this Agreement shall be terminated, will, upon
request, promptly deliver, and will use their best efforts to cause their agents
promptly to deliver, to the Company all copies of such information then in their
possession or control.

                                   ARTICLE II

                                   THE MERGER

2.1.    The Merger.

        Upon the terms and subject to the conditions set forth in this
Agreement, and in accordance with the Massachusetts Business Corporation Law
("MBCL"), Sub shall be merged with and into the Company at the Effective Time
(as defined in Section 2.3). Following the Effective Time, the separate
corporate existence of Sub shall cease and the Company shall continue as the
surviving corporation (the "Surviving Corporation") and shall succeed to and
assume all the rights and obligations of Sub in accordance with the MBCL.

2.2.    Closing.

        The closing of the Merger (the "Closing") will take place at 10:00 a.m.
(Connecticut time) on the first business day after the day on which the last to
be satisfied or waived of the conditions set forth in Article VIII (other than
those conditions that by their nature are to be satisfied at the Closing, but
subject to the fulfillment or waiver of those conditions) (the "Closing Date"),
at the offices of Wiggin & Dana, Three Stamford Plaza, Stamford, Connecticut
06911, unless another date, time or place is agreed to in writing by the parties
hereto.

2.3.    Effective Time.

        Subject to the provisions of this Agreement, as soon as practicable
after the Closing, the parties shall file articles of merger or other
appropriate documents (in any such case, the





                                       5









<PAGE>

"Articles of Merger") executed in accordance with the relevant provisions of the
MBCL and shall make all other filings or recordings required under the MBCL and
other applicable law. The Merger shall become effective at such time as the
Articles of Merger filed with the Secretary of the Commonwealth of the
Commonwealth of Massachusetts are duly accepted for record with the
Massachusetts Secretary of the Commonwealth (the time the Merger becomes
effective being hereinafter referred to as the "Effective Time").

2.4.    Effects of the Merger.

        The Merger shall have the effects set forth in the MBCL. The purpose of
the Surviving Corporation shall be to engage in the business of research related
to, and the development of proprietary products for, laboratory and clinical use
and to engage in any other business activity now or hereafter permitted by the
Commonwealth of Massachusetts to a corporation organized under Chapter 156B of
the MBCL.

2.5.    Articles of Organization and By-laws.

        (a) The Articles of Organization of the Company (the "Articles of
Organization"), as in effect immediately prior to the Effective Time, shall be
the articles of organization of the Surviving Corporation until thereafter
changed or amended as provided therein or by applicable law; provided, that
Parent shall be entitled, in its sole discretion, to amend and/or restate the
Articles of Organization simultaneously with the Effective Time.

        (b) The by-laws of Sub (the "By-laws") as in effect immediately prior to
the Effective Time shall be the by-laws of the Surviving Corporation, until
thereafter changed or amended as provided therein or by applicable law.

2.6.    Directors.

        The directors of Sub immediately prior to the Effective Time shall be
the directors of the Surviving Corporation, until the earlier of their death,
resignation or removal or until their respective successors are duly elected and
qualified, as the case may be.

2.7.    Officers.

        The officers of Sub and such other persons as designated by Parent
immediately prior to the Effective Time shall be the officers of the Surviving
Corporation, until the earlier of their resignation or removal or until their
respective successors are duly elected and qualified, as the case may be.




                                       6









<PAGE>

                                   ARTICLE III

          EFFECT OF THE MERGER ON THE CAPITAL STOCK OF THE CONSTITUENT
                     CORPORATIONS; EXCHANGE OF CERTIFICATES

3.1.    Effect on Capital Stock.

        As of the Effective Time, by virtue of the Merger and without any action
on the part of the holder of any Shares or any shares of capital stock of Sub:

        (a) Capital Stock of Sub. Each issued and outstanding share of capital
stock of Sub shall be converted into and become one fully paid and nonassessable
share of Common Stock, par value $.01 per share, of the Surviving Corporation.

        (b) Cancellation of Treasury Stock and Parent Owned Stock. Each share of
the Common Stock of the Company that is owned by the Company and each Share that
is owned by Parent or any other direct or indirect wholly owned subsidiary of
Parent shall automatically be canceled and retired and shall cease to exist, and
no consideration shall be delivered in exchange therefor.

        (c) Conversion of Company Common Stock. Subject to Section 3.1(d), each
issued and outstanding Share (other than shares to be canceled in accordance
with Section 3.1(b)) shall be converted into the right to receive from the
Surviving Corporation in cash, without interest, the price actually paid in the
Offer (the "Merger Consideration"). As of the Effective Time, all such Shares
shall no longer be outstanding and shall be canceled and retired automatically
and shall cease to exist, and each holder of a certificate representing any such
Shares shall cease to have any rights with respect thereto, except the right to
receive the Merger Consideration, without interest.

        (d) Shares of Dissenting Stockholders. Notwithstanding anything in this
Agreement to the contrary, any issued and outstanding Shares held by a person (a
"Dissenting Stockholder") who has neither voted in favor of the Merger nor
consented in writing thereto and otherwise complies with all the applicable
provisions of the MBCL concerning the right of holders of Company Common Stock
to dissent from the Merger and require appraisal of their Shares ("Dissenting
Shares") shall not be converted as described in Section 3.1(c) but shall become
the right to receive such consideration as may be determined to be due to such
Dissenting Stockholder pursuant to the laws of the Commonwealth of
Massachusetts. If, after the Effective Time, such Dissenting Stockholder
withdraws his demand for appraisal or fails to perfect or otherwise loses his
right of appraisal, in any case pursuant to the MBCL, his Shares shall be deemed
to be converted as of the Effective Time into the right to receive the Merger
Consideration. The Company shall give Parent (i) prompt notice of any demands
for appraisal of Shares received by the Company and (ii) if and after Sub shall
have accepted for payment Shares pursuant to and subject to the conditions of
the Offer (including the Minimum Condition), the opportunity to participate in
and direct all negotiations and proceedings with respect to any such demands.
The Company shall not, without the prior written consent of Parent, make any
payment with respect to, or settle, offer to settle or otherwise negotiate, any
such demands.




                                       7








<PAGE>

3.2.    Exchange of Certificates.

        (a) Paying Agent. Prior to the Effective Time, Parent shall designate a
commercial bank or trust company to act as paying agent in the Merger (the
"Paying Agent"). As of the Effective Time, Parent shall cause the Surviving
Corporation to deposit with the Paying Agent in separate trust for holders of
the Certificates (as hereinafter defined) cash in U.S. dollars in an amount
sufficient for the payment of the aggregate Merger Consideration for the shares
converted pursuant to Section 3.1(c) (it being understood that any and all
interest earned on funds made available to the Paying Agent pursuant to this
Agreement shall be turned over to Parent).

        (b) Exchange Procedure. As soon as reasonably practicable after the
Effective Time, the Paying Agent shall mail to each holder of record of a
certificate or certificates that immediately prior to the Effective Time
represented Shares (the "Certificates"), (i) a letter of transmittal (which
shall specify that delivery shall be effected, and risk of loss and title to the
Certificates shall pass, only upon delivery of the Certificates to the Paying
Agent and shall be in a form and have such other provisions as Parent may
reasonably specify) and (ii) instructions for use in effecting the surrender of
the Certificates in exchange for the Merger Consideration. Upon surrender of a
Certificate for cancellation to the Paying Agent or to such other agent or
agents as may be appointed by Parent, together with such letter of transmittal,
duly executed, and such other documents as may reasonably be required by the
Paying Agent, the holder of such Certificate shall be entitled to receive in
exchange therefor, and the Paying Agent shall pay pursuant to irrevocable
instructions given by Sub or Parent, the amount of cash into which the Shares
theretofore represented by such Certificate shall have been converted pursuant
to Section 3.1, and the Certificate so surrendered shall forthwith be canceled.
In the event of a transfer of ownership of Shares that is not registered in the
transfer records of the Company, payment may be made to a person other than the
person in whose name the Certificate so surrendered is registered, if such
Certificate shall be properly endorsed or otherwise be in proper form for
transfer and the person requesting such payment shall pay any transfer or other
taxes required by reason of the payment to a person other than the registered
holder of such Certificate or establish to the satisfaction of the Surviving
Corporation that such tax has been paid or is not applicable. Until surrendered
as contemplated by this Section, each Certificate shall be deemed at any time
after the Effective Time to represent only the right to receive upon such
surrender the amount of cash, without interest, into which the Shares
theretofore represented by such Certificate shall have been converted pursuant
to Section 3.1. No interest will be paid or will accrue on the cash payable upon
the surrender of any Certificate.

        (c) No Further Ownership Rights in Company Common Stock. All cash paid
upon the surrender of Certificates in accordance with the terms of this Article
III shall be deemed to have been paid in full satisfaction of all rights
pertaining to the Shares formerly represented by such Certificates. At the
Effective Time, the stock transfer books of the Company shall be closed, and
there shall be no further registration of transfers on the stock transfer books
of the Surviving Corporation of the Shares that were outstanding immediately
prior to the Effective Time. If, after the Effective Time, Certificates are
presented to the Surviving Corporation or the Paying Agent for any reason except
notation thereon that a stockholder has elected to exercise his right





                                       8








<PAGE>

to appraisal pursuant to the MBCL they shall be canceled and exchanged as
provided in this Article III.

        (d) No Liability. Any funds deposited with the Paying Agent that remain
unclaimed by the former stockholders of the Company for three (3) months after
the Effective Time shall be paid to the Surviving Corporation upon demand, and
any former stockholders of the Company who have not theretofore complied with
the instructions for exchanging their Certificates provided herein shall
thereafter look only to the Surviving Corporation for payment of their claims
for the Merger Consideration set forth in Section 3.1 hereof for each Share held
by such stockholder, without any interest thereon. None of Parent, Sub, the
Company or the Paying Agent shall be liable to any person in respect of any cash
delivered to a public official pursuant to any applicable abandoned property,
escheat or similar law. If any Certificates shall not have been surrendered
prior to seven years after the Effective Time (or immediately prior to such
earlier date on which any payment pursuant to this Article III would otherwise
escheat to or become the property of any Governmental Entity (as defined in
Section 4.5)), the cash payment in respect of such Certificate shall, to the
extent permitted by applicable law, become the property of the Surviving
Corporation, free and clear of all claims or interests of any person previously
entitled thereto.

                                   ARTICLE IV

                  REPRESENTATIONS AND WARRANTIES OF THE COMPANY

        The Company represents and warrants to Parent and Sub as follows:

4.1.    Organization.

        The Company is a corporation duly organized, validly existing and in
good standing under the laws of the Commonwealth of Massachusetts and has all
requisite corporate power and authority to carry on its business as now being
conducted. The Company is duly qualified or licensed to do business and in good
standing in each jurisdiction in which the property owned, leased or operated by
it or the nature of the business conducted by it makes such qualification or
licensing necessary, except in such jurisdictions where the failure to be so
duly qualified or licensed and in good standing has not had a material adverse
effect (as defined in Section 10.3) that has not been cured and reasonably would
not be expected to have a material adverse effect or prevent or materially delay
the consummation of the Offer and/or the Merger. The Company has made available
to Parent complete and correct copies of its Articles of Organization and By-
laws, as amended to the date hereof.

4.2.    Capitalization.

        The authorized capital stock of the Company consists of 10,000,000
Shares. At the close of business on May 26, 1999 (a) 3,468,202 Shares were
issued and outstanding, (b) no Shares were held by the Company in its treasury,
(c) 944,450 Shares were reserved for issuance upon





                                       9








<PAGE>

exercise of outstanding Company Stock Options (as defined in Section 7.4) and
(d) 305,000 Shares were issuable upon the exercise of outstanding Warrants (as
defined in Section 7.4. Since such date no shares of capital stock or other
voting securities of the Company were issued, reserved for issuance, issuable or
outstanding. All outstanding Shares are, and all Shares that may be issued will
be, when issued, duly authorized, validly issued, fully paid and nonassessable
and not subject to preemptive rights. There are no bonds, debentures, notes or
other indebtedness of the Company having the right to vote (or convertible into,
or exchangeable for, securities having the right to vote) on any matters on
which stockholders of the Company may vote. Except as set forth above, as of the
date hereof, there are no securities, options, warrants, calls, rights,
commitments, agreements, arrangements or undertakings of any kind to which the
Company is a party or by which any of them is bound obligating the Company to
issue, deliver or sell, or cause to be issued, delivered or sold, additional
shares of capital stock or other voting securities of the Company or obligating
the Company to issue, grant, extend or enter into any such security, option,
warrant, call, right, commitment, agreement, arrangement or undertaking. There
are no outstanding contractual obligations of the Company to repurchase, redeem
or otherwise acquire any shares of capital stock of the Company (other than as
set forth in Section 7.4).

4.3.    Subsidiaries.

        (a) The authorized capital stock of each of the subsidiaries of the
Company (the "Subsidiaries") is set forth on Schedule 4.3. All of the
outstanding shares of capital stock of the Subsidiaries are owned of record and
beneficially by the Company, free and clear of all mortgages, liens, pledges,
charges, encumbrances or other security interests (collectively, "Liens").

        (b) Except as set forth on Schedule 4.3, since December 31, 1998 no
shares of capital stock or other voting securities of any Subsidiary were
issued, reserved for issuance, issuable or outstanding. All outstanding shares
of capital stock of the Subsidiaries are, and all such shares which may be
issued will be, when issued, duly authorized, validly issued, fully paid and
nonassessable and not subject to preemptive rights. There are no bonds,
debentures, notes or other indebtedness of any Subsidiary having the right to
vote (or convertible into, or exchangeable for, securities having the right to
vote) on any matters on which stockholders of the Subsidiaries may vote. As of
the date hereof, there are no securities, options, warrants, calls, rights,
commitments, agreements, arrangements or undertakings of any kind to which the
Company or any Subsidiary is a party or by which any of them is bound obligating
the Company or any Subsidiary to issue, deliver or sell, or cause to be issued,
delivered or sold, additional shares of capital stock or other voting securities
of any Subsidiary or obligating the Company or any Subsidiary to issue, grant,
extend or enter into any such security, option, warrant, call, right,
commitment, agreement, arrangement or undertaking. There are no outstanding
contractual obligations of the Company or any Subsidiary to repurchase, redeem
or otherwise acquire any shares of capital stock of any Subsidiary. Except for
the Company's interest in its Subsidiaries or as set forth on Schedule 4.3,
neither the Company nor any Subsidiary owns directly or indirectly any interest
or investment in the form of debt or equity in, nor is the Company or any






                                       10








<PAGE>

Subsidiary subject to any obligation or requirement to provide for or to make
any such investment in, any person.

4.4.    Authority.

        The Company has the requisite corporate power and authority to execute
and deliver this Agreement and to consummate the transactions contemplated
hereby (other than, with respect to the Merger, the approval and adoption of
this Agreement by the holders of two-thirds of the Shares (the "Company
Stockholder Approval")). The execution, delivery and performance of this
Agreement by the Company and the consummation by the Company of the Merger and
of the other transactions contemplated hereby have been duly authorized by all
necessary corporate action on the part of the Company and no other corporate
proceedings on the part of the Company are necessary to authorize this Agreement
or to consummate the transactions so contemplated (in each case, other than,
with respect to the Merger, the Company Stockholder Approval). This Agreement
has been duly executed and delivered by the Company and, assuming due
authorization, execution and delivery by Parent and Sub, constitutes a valid and
binding obligation of the Company enforceable against the Company in accordance
with its terms, except as such enforceability may be limited by applicable
bankruptcy laws or creditors' rights generally or by general principles of
equity.

4.5.    Consents and Approvals; No Violations.

        Except for filings, permits, authorizations, consents and approvals (1)
as may be required under, and other applicable requirements of, the Exchange Act
(including the filing with the SEC of the Schedule 14D-9 and a proxy or
information statement relating to any required approval by or meeting of the
Company's stockholders of this Agreement (the "Proxy Statement")), and (2) with
the Secretary of the Commonwealth of Massachusetts, neither the execution,
delivery or performance of this Agreement by the Company nor the consummation by
the Company of the transactions contemplated hereby will require any filing
with, notice to, or Permit (as defined in Section 4.11), authorization, consent
or approval of, any Federal, state or local government or any court, tribunal,
administrative agency or commission or other governmental or other regulatory
authority or agency, domestic, foreign or supranational (a "Governmental
Entity"). Neither the execution, delivery or performance of this Agreement by
the Company nor the consummation by the Company of the transactions contemplated
hereby will (a) conflict with or result in any breach of any provision of the
Articles of Organization or By-laws of the Company or any of its Subsidiaries,
(b) result in the creation or imposition of any Liens upon the properties or
assets of the Company or any Subsidiary, (c) except as set forth on Schedule
4.5, result in a violation or breach of, require any notice to any party
pursuant to, or constitute (with or without due notice or lapse of time or both)
a default (or give rise to any right of termination, amendment, cancellation,
acceleration or right of non-renewal or contractually require any prepayment or
offer to purchase any debt or give rise to the loss of a material benefit)
under, any of the terms, conditions or provisions of any Commitment (as defined
in Section 4.10) to which the Company or any of its Subsidiaries is a party or
by which the Company's or any of its Subsidiaries' properties or assets may be
bound, (d) violate any order, writ, injunction, decree,





                                       11









<PAGE>

statute, rule or regulation applicable to the Company or any of its Subsidiaries
or any of their respective properties or assets or (e) result in the loss,
forfeiture, revocation, termination or diminution of any Permit (as defined in
Section 4.11) except in the case of clauses (c), (d) or (e) for failures to
fulfill requirements, losses, forfeitures, revocations, diminutions, violations,
breaches or defaults that, individually or in the aggregate, have not had an
adverse effect that has not been cured and reasonably would not be expected to
have an adverse effect or prevent or delay the consummation of the Offer and/or
the Merger.

4.6.    SEC Documents; Financial Statements; Other Financial Information.

        (a) The Company has filed with the SEC all reports, forms, schedules and
statements and other documents required to be filed by it (the "SEC Documents").
As of their respective filing dates, (i) the SEC Documents complied in all
material respects with the requirements of the Securities Act of 1933, as
amended (the Securities Act"), or the Exchange Act, as the case may be, and the
rules and regulations of the SEC promulgated thereunder applicable to such SEC
Documents, and (ii) none of the SEC Documents contained any untrue statement of
a material fact or omitted to state a material fact required to be stated
therein or necessary in order to make the statements therein, in light of the
circumstances under which they were made, not misleading. The financial
statements included in the SEC Documents complied, as of their respective filing
dates as to form in all material respects with applicable accounting
requirements and the published rules and regulations of the SEC with respect
thereto, were prepared in accordance with generally accepted accounting
principles (except, in the case of unaudited statements, as permitted by Form
10-QSB of the SEC) applied on a consistent basis during the periods involved
(except as may be indicated in the notes thereto) and fairly present, in all
material respects, the consolidated financial position of the Company and its
Subsidiaries as of the dates thereof and the results of its operations and cash
flows for the periods then ended (subject, in the case of unaudited statements,
to normal year-end audit adjustments). Except as set forth on Schedule 4.6 or in
the SEC Documents filed and publicly available prior to the date hereof, and
except for liabilities and obligations incurred in the ordinary course of
business consistent with past practice since the date of the most recent
consolidated balance sheet included in the SEC Documents filed and publicly
available prior to the date hereof, neither the Company nor any of its
Subsidiaries has any liabilities or obligations of any nature (whether accrued,
absolute, contingent or otherwise) required by generally accepted accounting
principles to be set forth on a balance sheet or in the notes thereto.

        (b) All accounts receivable of the Company and each Subsidiary have
arisen from bona fide services provided in the ordinary course of business to
third parties which are not Affiliates (as defined in Rule 405 promulgated under
the Securities Act) of the Company or any Subsidiary or any of their officers,
directors or employees. All accounts receivable are good and collectible in the
ordinary course of business consistent with past practice at the aggregate
recorded amounts thereof, subject to reserves taken consistent with past
practices.

        (c) Schedule 4.6(c) sets forth the consolidated indebtedness owed by the
Company and its Subsidiaries to any third party, and the Company's aggregate
consolidated cash and cash equivalents, each calculated as of May 24, 1999 in
accordance with generally accepted





                                       12









<PAGE>

accounting principles, consistently applied. The term "indebtedness" shall
include indebtedness for borrowed money, reimbursement obligations with respect
to letters of credit and similar instruments, obligations incurred, issued or
assumed as the deferred purchase price of property or services (other than
accounts payable incurred in the ordinary course of business consistent with
past practice), obligations of others secured by (or, for which the holder of
such indebtedness has an existing right, contingent or otherwise, to be secured)
any Lien on property or assets of the Company or any Subsidiary, capital lease
obligations, and obligations in respect of guarantees of any of the foregoing or
any "keep well" or other agreement to maintain any financial statement condition
of another person, in each case, whether or not matured, liquidated, fixed,
contingent, or disputed.

4.7.    Information Supplied.

        None of the information supplied or to be supplied by the Company for
inclusion or incorporation by reference in (a) the Offer Documents, (b) the
Schedule 14D-9, (c) the information to be filed by the Company in connection
with the Offer pursuant to Rule 14f-1 promulgated under the Exchange Act (the
"Information Statement") or (d) the Proxy Statement, will, in the case of the
Offer Documents, the Schedule 14D-9 and the Information Statement at the
respective times the Offer Documents, the Schedule 14D-9 and the Information
Statement are filed with the SEC or first published, sent or given to the
Company's stockholders, or in the case of the Proxy Statement, at the time the
Proxy Statement is first mailed to the Company's stockholders or at the time of
the Stockholders Meeting (as defined in Section 7.1) contain any untrue
statement of a material fact or omit to state any material fact required to be
stated therein or necessary in order to make the statements therein, in light of
the circumstances under which they are made, not misleading. The Schedule 14D-
9, the Information Statement and the Proxy Statement will comply as to form in
all material respects with the requirements of the Exchange Act and the rules
and regulations thereunder, except that no representation or warranty is made by
the Company with respect to statements made or incorporated by reference therein
based on information supplied by Parent or Sub specifically for inclusion or
incorporation by reference therein.

4.8.    Absence of Certain Changes or Events.

        Except as disclosed in the SEC Documents (including exhibits thereto)
filed since January 1, 1998 and publicly available prior to the date hereof (the
"Filed SEC Documents"), and except as set forth on Schedule 4.8, since the date
of the most recent audited financial statements included in the Filed SEC
Documents, the Company and its Subsidiaries have conducted their respective
businesses only in the ordinary course consistent with prior practice, and there
has not been (a) any material adverse change, (b) any declaration, setting aside
or payment of any dividend or other distribution (whether in cash, stock or
property) with respect to any of the Company's capital stock, (c) any split,
combination or reclassification of any of its capital stock or any issuance or
the authorization of any issuance of any other securities in respect of, in lieu
of or in substitution for shares of its capital stock, (d) (i) any granting by
the Company or any Subsidiary to any officer of the Company of any increase in
compensation,





                                       13







<PAGE>

except in the ordinary course of business consistent with past practice as was
required under employment agreements in effect as of the date of the most recent
audited financial statements included in the Filed SEC Documents, (ii) any
granting by the Company or any Subsidiary to any officer, employee, director or
consultant of any increase in severance or termination pay, except as was
required under any employment, severance or termination agreements in effect as
of the date of the most recent audited financial statements included in the
Filed SEC Documents or (iii) any entry by the Company or any Subsidiary into any
employment, severance or termination agreement with any officer, employee,
director or consultant, (e) any damage, destruction or loss to property, whether
or not covered by insurance, that, individually or in the aggregate, has not
been cured and would be reasonably expected to have, individually or in the
aggregate, a material adverse effect, (f) any change in accounting methods,
principles or practices by the Company or any Subsidiary, (g) any delivery of a
notice of non-renewal or any other failure to renew contracts or agreements to
which the Company or any Subsidiary is a party which are material, individually
or in the aggregate, or (h) any loss of any employee who earned more than
$75,000 in the most recent fiscal year (in salary, bonus and other cash
compensation).

4.9.    Litigation.

        Except as disclosed on Schedule 4.9 hereto, there is no claim, suit,
action, proceeding or investigation pending or, to the knowledge of the Company,
threatened against or affecting the Company or any of its Subsidiaries and there
is no judgment, decree, injunction, rule or order of any Governmental Entity or
arbitrator outstanding against the Company or any Subsidiary.

4.10.   Contracts.

        Except as filed as an exhibit to the Filed SEC Documents or set forth on
Schedule 4.10 and delivered to or made available to Parent or its counsel, there
are no (a) notes, bonds, mortgages, indentures, leases, or Permits, or (b) other
contracts, agreements or other instruments or obligations, whether written or
oral, or any amendments, supplements or restatements of any of the foregoing
((a) and (b), collectively, "Commitments") that (i) relate to real property and
involve payments in excess of $25,000 annually, (ii) relate to goods or services
provided by the Company and involve payments in excess of $25,000 annually,
(iii) relate to employees, officers, or directors of the Company or independent
contractors performing services on behalf of the Company or (iv) are otherwise
material to the business, financial condition or results of operations of the
Company and its Subsidiaries, taken as a whole. Neither the Company nor any
Subsidiary is and, to the knowledge of the Company, no other party is in
violation of or in default under (nor does there exist any condition which upon
the passage of time or the giving of notice or both would reasonably be expected
to cause such a violation of or default under) any material Commitment to which
it is a party or by which it or any of its properties or assets is bound. Each
Commitment constitutes a valid and binding obligation on the Company and/or the
Subsidiary party thereto and, to the knowledge of the Company, each other party
thereto, enforceable against such other party in accordance with its terms,
except as such enforceability may be limited by applicable bankruptcy laws or
creditors' rights generally or by general principles of equity.




                                       14








<PAGE>

4.11.   Compliance with Laws.

        The Company and each Subsidiary is in compliance with all applicable
statutes, laws, codes, ordinances, regulations, rules, Permits, judgments,
decrees and orders of any Governmental Entity applicable to its assets,
properties, business or operations. The Company and each Subsidiary has in
effect all Federal, state, local and foreign governmental approvals,
authorizations, certificates, filings, franchises, licenses, notices, permits
and rights, including all certificates of need and authorizations under
Environmental Laws (as defined below) and exemptions from any of the foregoing
(collectively, "Permits") necessary for it to own, lease or operate its
properties and assets and to carry on its business as now conducted (and the
Company and/or each Subsidiary has timely made appropriate filings for issuance
or renewal thereof). Schedule 4.11 contains a list of all Permits, and copies
thereof have been provided to Parent or its counsel. No default under any Permit
has occurred. No investigation or review by any Governmental Entity with respect
to the Company or any Subsidiary is pending or, to the knowledge of the Company,
threatened.

4.12.   Environmental Matters.

        Except as set forth in Schedule 4.12:

        (a) the Company and each Subsidiary is, and has been, in compliance with
all applicable Environmental Laws (as defined below). The term "Environmental
Laws" means any Federal, state, provincial, regional, municipal, local or
foreign judgment, order, decree, statute, law, ordinance, rule, regulation,
code, permit, consent, approval, license, writ, decree, directive, injunction or
other enforceable requirement, including any registration requirement, relating
to: (A) Releases (as defined below) or threatened Releases of Hazardous
Materials (as defined below) into the environment; (B) the generation,
treatment, storage, disposal, use, handling, manufacturing, transportation or
shipment of Hazardous Materials; or (C) otherwise relating to pollution or
protection of health or safety or the environment;

        (b) there has been no Release or threatened Release of Hazardous
Materials by the Company or any Subsidiary, or the knowledge of the Company by
any other party, in, on, under or affecting any property now or previously
owned, leased, controlled or operated by the Company or any Subsidiary or, to
the knowledge of the Company, any adjacent site. The term "Release" has the
meaning set forth in 42 U.S.C. (S) 9601(22). The term "Hazardous Materials"
means any pollutant, contaminant, hazardous, radioactive or toxic substance,
material, constituent or waste, or any other waste, substance, chemical or
material regulated under any Environmental Law, including (1) petroleum, crude
oil and any fractions thereof, (2) natural gas, synthetic gas and any mixtures
thereof, (3) asbestos and/or asbestos-containing material, (4) radon and (5)
polychlorinated biphenyls ("PCBs"), or materials or fluids containing PCBs;

        (c) there is no pending, or, to the knowledge of the Company, threatened
claim, action, demand, investigation or inquiry by any Governmental Entity or
other person relating to any





                                       15









<PAGE>

actual or potential violations of Environmental Law or any actual or potential
obligation to investigate or remediate a Release or threatened Release of any
Hazardous Materials;

        (d) neither the Company nor any Subsidiary has assumed, whether by
contract or operation of law, any liabilities or obligations arising under
Environmental Laws in connection with formerly owned, leased or operated
properties or facilities or in connection with any formerly owned divisions,
subsidiaries, companies or other entities; and

        (e) there are no underground or aboveground storage tanks, incinerators
or surface impoundments owned or operated by the Company or any Subsidiary, or
to the knowledge of the Company, by any other party at, on or under or within
any property, owned, leased, controlled or operated by the Company or any
Subsidiary, except as are in compliance with Environmental Laws and no such
tanks, incinerators or impoundments have been removed from any such property;
and

        (f) neither the Company nor any Subsidiary has used any waste disposal
site, or otherwise disposed of, transported, or arranged for the transportation
of, any Hazardous Materials to any place or location, except in compliance with
all applicable Environmental Laws and for any such use, disposal, transportation
or arrangement that has not had a material adverse effect.

4.13.   Absence of Changes in Benefit Plans; Labor Relations.

        Except as filed as an exhibit to the Filed SEC Documents and except as
disclosed on Schedule 4.13 or as expressly provided in this Agreement, since the
date of the most recent audited financial statements included in the Filed SEC
Documents, there has not been any adoption or amendment in any material respect
by the Company or any Subsidiary of any collective bargaining agreement or any
bonus, pension, profit sharing, deferred compensation, incentive compensation,
stock ownership, stock purchase, stock option, phantom stock, retirement,
vacation, severance, disability, death benefit, hospitalization, medical or
other plan or arrangement providing benefits to any current or former employee,
officer or director of the Company or any Subsidiary. Except as set forth in
Schedule 4.13 or as filed as an exhibit to the Filed SEC Documents or as
expressly provided in this Agreement, there exist no employment, consulting,
severance, termination or indemnification agreements or arrangements between the
Company and any current or former employee, officer or director of the Company.
Schedule 4.13 contains a list of all amounts payable or that will or may become
payable to each director, officer or employee or former director, officer or
employee of the Company or any Subsidiary pursuant to any employment,
change-in-control, severance or termination agreement or arrangement other than
pursuant to the Employment Agreements. There are no collective bargaining or
other labor union agreements to which the Company or any Subsidiary is a party
or by which it is bound. To the knowledge of the Company, the Company has not
encountered any labor union organizing activity, or had any actual or threatened
employee strikes, work stoppages, slowdowns or lockouts.



                                       16








<PAGE>

4.14.   Employment Matters; Affiliate Transactions.

        (a) Schedule 4.14 sets forth a list of all directors, officers and
employees of the Company and each Subsidiary as of the date hereof and the
aggregate salary, bonus and other cash compensation paid as of May 14, 1999 and
the number of Company Stock Options and/or Warrants granted or issued to each
such employee, officer, and director in the most recently completed fiscal year
and paid and granted or issued to each such person from the beginning of the
current fiscal year to the date hereof. Since May 14, 1999, the Company has not
increased the annual salary, bonus or other cash compensation payable to any
director, officer or employee of the Company except as may be provided in the
Employment Agreements.

        (b) Schedule 4.14 sets forth a list of all outstanding Company Stock
Options and Warrants as of the date hereof, showing for each such Company Stock
Option and Warrant: (i) the number of Shares issuable, (ii) the number of vested
Shares, (iii) the date of grant, (iv) the exercise price and (v) the holder
thereof.

        (c) Schedule 4.14 sets forth a description of all transactions between
the Company or its Subsidiaries, on the one hand, and any of their respective
Affiliates, directors, officers, employees, or consultants, on the other hand,
in each case consummated at any time since January 1, 1998. Except as set forth
on Schedule 4.14, there are no agreements or arrangements between the Company or
its Subsidiaries, on the one hand, and any of their respective Affiliates,
directors, officers, employees or consultants, on the other hand, with respect
to any such transactions. No Affiliate, director, officer, employee or
consultant of the Company owns any interest in any asset or property (real or
personal, tangible or intangible), business or contract used or intended for use
or otherwise relating to the business currently conducted or proposed to be
conducted by the Company or any Subsidiary.

4.15.   ERISA Compliance.

        (a) Schedule 4.15(a) contains a list of all "employee pension benefit
plans" (as defined in Section 3(2) of the Employee Retirement Income Security
Act of 1974, as amended ("ERISA")) (sometimes referred to herein as "Pension
Plans"), "employee welfare benefit plans" (as defined in Section 3(1) of ERISA)
and all other benefit plans, contracts, programs, policies, practices or
arrangements, whether written or oral, funded or unfunded, maintained or
contributed to by the Company or any other person or entity that, together with
the Company, is treated as a single employer under Section 414(b), (c), (m) or
(o) of the Internal Revenue Code of 1986, as amended (the "Code") (the Company
and each such other person or entity, a "Commonly Controlled Entity"), for the
benefit of any current or former employees, officers or directors of the Company
or dependents of any such person (collectively, "Benefit Plans"). The Company
has delivered or made available to Parent true, complete and correct copies of
(i) each Benefit Plan (or, in the case of any unwritten Benefit Plans,
descriptions thereof), (ii) the most recent annual report on Form 5500 filed
with the Internal Revenue Service with respect to each Benefit Plan (if any such
report was required), (iii) the most recent summary plan description for each
Benefit Plan for which such summary plan description is required and (iv) each
trust agreement and group annuity contract relating to any Benefit Plan. Each
Benefit Plan has been





                                       17









<PAGE>

administered in all material respects in accordance with its terms. The Company
and each Commonly Controlled Entity and all the Benefit Plans are all in
compliance in all material respects, and all Benefit Plans have been operated
and administered in all material respects with applicable provisions of ERISA
and the Code, and no "reportable event," or non-exempt "prohibited transaction"
(as such terms are defined in ERISA and the Code, as applicable), or termination
has occurred with respect to any Benefit Plan, and the consummation of the
transaction entered into pursuant to this Agreement will not result in the
occurrence of any such event.

        (b) Except as disclosed in Schedule 4.15(b), all Pension Plans intended
to qualify under Section 401(a) of the Code are qualified and exempt from
Federal income taxes under Section 401(a) and 501(a), respectively, of the Code,
and no event has occurred that would adversely affect its qualification or
materially increase its costs. All amendments to Pension Plans required under
ERISA and the Code to be adopted by the Company by December 31, 1994, have been
adopted. There have been no material violations of ERISA or the Code with
respect to the filing of applicable documents, notices or reports (including,
without limitation, annual reports filed on IRS From 5500) relating to any
Benefit Plan maintained by the Company or any Commonly Controlled Entity with
any Governmental Authority or the furnishing of such required documents to the
participants or beneficiaries of such Benefit Plans.

        (c) Neither the Company nor any Commonly Controlled Entity has within
the five year period immediately preceding the date hereof maintained,
contributed to or been obligated to contribute to any Benefit Plan that is
subject to Title IV of ERISA or Section 412 of the Code. Neither the Company nor
any Commonly Controlled Entity is required to contribute to any "multiemployer
plan" (as defined in Section 4001(a) (3) of ERISA) or has withdrawn from any
multiemployer plan where such withdrawal has resulted or would result in any
"withdrawal liability" (within the meaning of Section 4201 of ERISA) that has
not been fully paid.

        (d) With respect to any Benefit Plan that is an employee welfare benefit
plan, except as disclosed in Schedule 4.15(d), (1) no such Benefit Plan is
funded through a "welfare benefits fund", as such term is defined in Section 419
(e) of the Code, (2) each such Benefit Plan that is a "group health plan", as
such term is defined in Section 5000 (b)(1) of the Code, complies substantially
with the applicable requirements of Section 4980B(f) of the Code and (3) except
as provided in writing in such plan, there are no understandings, agreements or
undertakings, written or oral, that would prevent any such plan (including any
such plan covering retirees or other former employees) from being amended or
terminated without material liability to the Company or any Commonly Controlled
Entity on or at any time after the Effective Time. Except as set forth in
Schedule 4.15(d), no Benefit Plan that is a welfare benefit plan provides for
post-retirement medical or life insurance benefits coverage to any current or
former employee, officer, or director of the Company or any dependent of any
such individual except as may be required by the Consolidated Omnibus Budget
Reconciliation Act of 1985, as amended ("COBRA"), and the Health Insurance
Portability and Accountability Act of 1996; and there are no qualified
beneficiaries that have elected COBRA coverage under an employee welfare benefit
plan as of the Closing Date.





                                       18










<PAGE>

        (e) Except as set forth on Schedule 4.15(e) and except with respect to
the Company Stock Options, no employee or director of the Company will be
entitled to any additional compensation or benefits or any acceleration of the
time of payment or vesting of any compensation or benefits under any Benefit
Plan as a result of the transactions contemplated by this Agreement. It shall be
assumed for purposes of the preceding sentence that no payments will be received
by, or accelerated to, any such employee or director as a result of the
termination of such individual's employment/service relationship by the
Surviving Corporation after the Effective Time.

        (f) All contributions (including all employer contributions and employee
salary reduction contributions) which are due to each Benefit Plan which is a
Pension Plan have been timely paid.

        (g) To the Company's knowledge, after due inquiry, there has been no act
or acts which would result in the disallowance of an income tax deduction that
would otherwise be available to the Company or the imposition of a tax, an
addition to tax or a penalty pursuant to Code Sections 4980B, 4980D, 4975, 4972,
6652, 6721 or 6723 or any predecessor provision thereof, or any regulations
promulgated thereunder, whether final, temporary or proposed.

        (h) The Company does not maintain and has not ever maintained any
nonqualified deferred compensation arrangements, including, but not limited to,
"top-hat" plans within the meaning of ERISA Section 201(2).

4.16.   Taxes.

        Except as set forth on Schedule 4.16, Company has filed all tax returns
and reports required to be filed by it (which returns are true and complete in
all material respects) and has paid all taxes due and required to be paid by it
(other than such taxes as are being contested in good faith or with respect to
which the Company is maintaining reserves). The most recent financial statements
contained in the Filed SEC Documents reflect an adequate reserve for all taxes
payable by the Company or any Subsidiary for all taxable periods and portions
thereof through the date of such financial statements. Except as set forth on
Schedule 4.16, no deficiencies for any taxes which remain outstanding have been
proposed, asserted or assessed against the Company or any Subsidiary, and no
requests for waivers of the time to assess any such taxes are pending. Except as
set forth on Schedule 4.16, none of the Federal income tax returns of the
Company or any Subsidiary have been examined by the United States Internal
Revenue Service. As used in this Agreement, "taxes" shall mean all Federal,
state, local and foreign income, property, sales, payroll, employment, excise,
withholding and other taxes, tariffs or other governmental charges in the nature
of a tax as well as any interest, penalties and additions to tax.

4.17.   No Excess Parachute Payments.

        Not including any payments under the Employment Agreements, no amount
that could be received pursuant to the Benefit Plans or any executed and
delivered agreements between the





                                       19








<PAGE>

Company or any Subsidiary and any officer, director or employee thereof in
effect as of the date hereof (whether in cash or property or the vesting of
property) as a result of any of the transactions contemplated by this Agreement
by any employee, officer or director of the Company or any Subsidiary who is a
"disqualified individual" (as such term is defined in proposed Treasury
Regulation Section 1.280G-1) under any employment, severance, change-in-control
or termination agreement, other compensation arrangement or Benefit Plan
currently in effect would be an "excess parachute payment" (as such term is
defined in Section 280G(b) (1) of the Code). No disqualified individual is
entitled to receive any additional payment from the Company, any Subsidiary, the
Surviving Corporation, or any other person referred to in Q&A 10 under proposed
Treasury Regulation Section 1.280G-1 (a "Parachute Gross-Up Payment") in the
event that the 20 per cent parachute excise tax of Section 4999(a) of the Code
is imposed on such person. Except as set forth in Schedule 4.17, neither the
Board of Directors of the Company nor the Board of Directors of any Subsidiary
has during the six months prior to the date hereof granted to any officer,
director or employee of the Company or any Subsidiary any right to receive any
Parachute Gross-Up Payment.

4.18.   Title to Properties; Condition of Assets.

        (a) Except as set forth in Schedule 4.18, the Company and each
Subsidiary has good and marketable title to, or valid leasehold interests in,
all its material properties and assets except for such as are no longer used in
the conduct of its businesses or as have been disposed of in the ordinary course
of business. All such assets and properties are free and clear of all Liens
other than those set forth in Schedule 4.18.

        (b) The properties and assets of the Company and its Subsidiaries are in
good repair and operating condition, and are sufficient for the conduct of the
business of the Company and the Subsidiaries as presently conducted.

        (c) Except as set forth in Schedule 4.18, the Company and each
Subsidiary has complied in all material respects with the terms of all leases to
which it is a party or under which it is in occupancy, and all such leases are
in full force and effect. The Company enjoys peaceful and undisturbed possession
under all such leases.

        (d) Neither the Company nor any Subsidiary owns any real property.

4.19.   Intellectual Property.

        (a) For the purposes of this Section 4.19, "Intellectual Property" means
(i) all patents, trademarks, trade names, and applications for any of the
foregoing, of any party, or to which it has rights and (ii) all licenses granted
by or to such party, and other agreements pertaining to any of the foregoing or
any inventions, trade secrets or other proprietary know-how to which such party
is a party or is bound. The Company has disclosed to Parent or its counsel
correct and complete copies of all applications, filings, licenses, agreements
and related correspondence and documents embodying the Company's Intellectual
Property.




                                       20







<PAGE>

        (b) Except as set forth in Schedule 4.19: (i) the Company owns or has
the right to use all of the Company's Intellectual Property necessary for the
Company to conduct its business as presently conducted; (ii) no proceedings have
been instituted, are pending or, to the best of its knowledge, threatened, which
challenge the Company's rights in respect of the aforesaid or the validity
thereof; (iii) none of the Intellectual Property owned or used by the Company is
the subject of any lien or other agreement granting rights therein to any third
party; (iv) the Company has not received notice of any charges of interference
or infringement of any Intellectual Property; (v) to the Company's knowledge, no
method or product used by the Company (A) infringes upon or otherwise violates
the Intellectual Property rights of others and the Company has not received any
claims of such infringements or violation; and (B) none of the Company's patents
is being infringed by others and none is subject to any outstanding order,
decree, judgment, stipulation or charge; (vi) the Company's employees and
consultants who are engaged to develop Intellectual Property are required to
sign confidentiality and assignment of inventions agreements in the form
previously provided Sub; (vii) the Company has no knowledge of any facts or
claims which would cause any of such patents, trademarks, or copyrights to be
invalid; and (viii) the Company's Intellectual Property was not developed under
a grant from any Governmental Entity or private source.

4.20.   Non-Compete.

        Except as set forth in Schedule 4.20, neither the Company nor any
Subsidiary is subject to any agreement, covenant or understanding that restricts
the Company or any Subsidiary from entering or conducting any line of business
in any location at any time.

4.21.   Voting Requirements.

        The affirmative vote of the holders of two-thirds of the outstanding
Shares is the only vote of the holders of any class or series of the Company's
capital stock necessary to approve the Merger.

4.22.   State Takeover Statutes.

        The Board of Directors of the Company has approved the Merger and this
Agreement, and such approval is sufficient to render inapplicable to the Merger,
this Agreement and the transactions contemplated by this Agreement, the
provisions of Chapter 110C of the General Laws of the Commonwealth of
Massachusetts to the extent, if any, such Chapter is applicable to the Merger,
this Agreement and the transactions contemplated by this Agreement and the
Stockholder Agreement. To the Company's knowledge, no other state takeover
statute or similar statute or regulation applies or purports to apply to the
Merger, this Agreement or the transactions contemplated by this Agreement.




                                       21








<PAGE>

4.23.   Brokers.

        Except as set forth on Schedule 4.23, no broker, investment banker,
financial advisor or other person, other than AH&H, the fees and expenses of
which will be paid by the Company, is entitled to any broker's, finder's,
financial advisor's or other similar fee or commission in connection with the
transactions contemplated by this Agreement based upon arrangements made by or
on behalf of the Company.

4.24.   Opinion of Financial Advisor.

        The Board of Directors of the Company has received the opinion of AH&H
dated the date of this Agreement to the effect that, as of such date and based
upon and subject to the matters set forth therein, the cash consideration to be
received by holders of Shares (other than Parent and its Affiliates) pursuant to
the Offer and the Merger is fair from a financial point of view to such holders
and a complete and correct signed copy of which opinion has been delivered to
Parent (after receipt thereof by the Company).

4.25.   Year 2000.

        The description of the Company's Year 2000 readiness under the caption
"Management's Discussion and Analysis of Financial Condition and Results of
Operations--Year 2000" in the Company's Form 10-KSB for the year ended May 31,
1998 is accurate and complete in all respects.

                                    ARTICLE V

                REPRESENTATIONS AND WARRANTIES OF PARENT AND SUB

        Parent and Sub each represent and warrant to the Company as follows:

5.1     Organization.

        (a) Each of Parent and Sub is a corporation duly organized, validly
existing and in good standing under the laws of the jurisdiction of its
incorporation and has all requisite corporate power and authority to carry on
its business as now being conducted. Each of Parent and Sub is duly qualified or
licensed to do business and is in good standing in each jurisdiction in which
the nature of its business or the ownership or leasing of its properties makes
such qualifications or licensing necessary, other than in such jurisdictions
where the failure to be so qualified or licensed (individually or in the
aggregate) could not be reasonably expected to prevent or materially delay the
consummation of the Offer and/or the Merger.




                                       22








<PAGE>

        (b) All of the issued and outstanding capital stock of Sub is, and at
the Effective Time will be, owned by Parent, and there are no (i) other
outstanding shares of capital stock or other voting securities of Sub, (ii)
securities of Sub convertible into or exchangeable for shares of capital stock
or other voting securities of Sub or (iii) options or other rights to acquire
from Sub, and no obligations of Sub to issue, any capital stock, other voting
securities or securities convertible into or exchangeable for capital stock or
other voting securities of Sub. Sub has made available to the Company a complete
and correct copy of Sub's articles of organization and bylaws, as amended to the
date hereof. Sub's articles of organization and bylaws so delivered are in full
force and effect and will remain in full force and effect until the Effective
Time.

5.2     Authority.

        Parent and Sub have requisite power and authority to execute and deliver
this Agreement and the Stockholder Agreement, and to consummate the transactions
contemplated by this Agreement and the Stockholder Agreement. The execution,
delivery and performance of this Agreement and the Stockholder Agreement, and
the consummation of the transactions contemplated by this Agreement and the
Stockholder Agreement, have been duly authorized by all necessary action on the
part of Parent and Sub and no other proceedings on the part of Parent and Sub
are necessary to authorize this Agreement or the Stockholder Agreement or to
consummate the transactions contemplated hereby or thereby. No vote of Parent
shareholders is required to approve this Agreement or the Stockholder Agreement
or the transactions contemplated hereby or thereby. Each of this Agreement and
the Stockholder Agreement has been duly executed and delivered by Parent and Sub
and constitutes a valid and binding obligation of Parent and Sub enforceable
against Parent and Sub in accordance with its terms.

5.3     Consents and Approvals; No Violations.

        Except for filings, permits, authorizations, consents and approvals as
may be required under, and other applicable requirements of, the Exchange Act
(including the filing with the SEC of the Offer Documents), the MBCL and state
takeover laws, neither the execution, delivery or performance of this Agreement
or the Stockholder Agreement by Parent and Sub, nor the consummation by Parent
and Sub of the transactions contemplated hereby or thereby will (i) conflict
with or result in any breach of any provision of the respective certificate of
incorporation or by-laws of Parent and Sub, (ii) require any filing with, notice
to, or permit, authorization, consent or approval of, any Governmental Entity
(except where the failure to obtain such permits, authorizations, consents or
approvals or to make such filings would not reasonably be expected to prevent or
materially delay the consummation of the Offer and/or the Merger), (iii) result
in a violation or breach of, require any notice to any party pursuant to, or
constitute (with or without due notice or lapse of time or both) a default (or
give rise to any right of termination, amendment, cancellation or acceleration)
under, any of the terms, conditions or provisions of any note, bond, mortgage,
indenture, license, lease, contract, agreement or other instrument or obligation
to which Parent or any of its subsidiaries is a party or by which any of them or
any of their properties or assets may be bound or (iv) violate any order, writ,
injunction, decree, statute, rule or regulation applicable to Parent, any of its
subsidiaries or any of their properties or assets,






                                       23








<PAGE>

except in the case of clauses (iii) and (iv) for violations, breaches or
defaults which could not, individually or in the aggregate, be reasonably
expected to prevent or materially delay the consummation of the Offer and/or the
Merger.

5.4     Information Supplied.

        None of the information supplied or to be supplied by Parent or Sub
specifically for inclusion or incorporation by reference in (i) the Offer
Documents, (ii) the Schedule 14D-9, (iii) the Information Statement or (iv) the
Proxy Statement will, in the case of the Offer Documents, the Schedule 14D-9 and
the Information Statement, at the respective times the Offer Documents, the
Schedule 14D-9 and the Information Statement are filed with the SEC or first
published, sent or given to the Company's stockholders, or, in the case of the
Proxy Statement, at the time the Proxy Statement is first mailed to the
Company's stockholders or at the time of the Stockholders Meeting, contain any
untrue statement of a material fact or omit to state any material fact required
to be stated therein or necessary in order to make the statements therein, in
light of the circumstances under which they are made, not misleading. The Offer
Documents will comply as to form in all material respects with the requirements
of the Exchange Act and the rules and regulations thereunder, except that no
representation or warranty is made by Parent or Sub with respect to statements
made or incorporated by reference therein based on information supplied by or on
behalf of the Company specifically for inclusion or incorporation by reference
therein.

5.5     Interim Operations of Sub.

        Sub (and any other wholly owned subsidiary of Parent which may be used
to effect the Offer and the Merger pursuant to Section 2.1) was formed solely
for the purpose of engaging in the transactions contemplated hereby, has engaged
in no other business activities and has conducted its operations only as
contemplated hereby.

5.6     Brokers.

        No broker, investment banker, financial advisor or other person other
than Vector Securities International, Inc., the fees and expenses of which shall
be paid by the Parent, is entitled to any broker's, finder's, financial
advisor's or other similar fee or commission in connection with the transactions
contemplated by this Agreement based upon arrangements made by or on behalf of
Parent or Sub.

5.7     Financing.

        Parent has, and on the Expiration Date will have, sufficient funds
available, directly or through finance commitments, to purchase, or to cause Sub
to purchase, all the Shares pursuant to the Offer and the Merger and to pay all
fees and expenses payable by Parent or Sub related to the transactions
contemplated by this Agreement.





                                       24








<PAGE>

                                   ARTICLE VI

                                    COVENANTS

6.1     Conduct of Business.

        From the date hereof to the Effective Time, the Company shall, and shall
cause each Subsidiary to, carry on its business in the ordinary course
consistent with past practice and use its best efforts to preserve intact its
current business organization, keep available the services of its current
officers and employees as appropriate and preserve its relationships with
customers, suppliers, licensors, licensees and others having significant
business dealings with it. Without limiting the generality of the foregoing,
from the date hereof to the Effective Time, the Company shall not and shall
cause each Subsidiary not to (unless Parent shall otherwise approve in writing,
which approval shall not be unreasonably withheld or delayed, and except as
expressly permitted by this Agreement):

        (a) (i) declare, set aside or pay any dividends on, or make any other
distributions in respect of, any of its capital stock, (ii) split, combine or
reclassify any of its capital stock or issue or authorize the issuance of any
other securities in respect of, in lieu of or in substitution for Shares of its
capital stock, or (iii) purchase, redeem or otherwise acquire any Shares or any
capital stock of the Company or any Subsidiary or any other securities thereof
or any rights, warrants or options to acquire any such shares or other
securities;

        (b) issue, deliver, sell, pledge or otherwise encumber any shares of its
capital stock, any other voting securities or any securities convertible into,
or any rights, warrants or options to acquire, any such shares, voting
securities or convertible securities (other than the issuance of Shares upon the
exercise of Company Stock Options or warrants to purchase Shares outstanding on
the date hereof in accordance with their present terms);

        (c) amend its Articles of Organization or Bylaws or other comparable
charter or organizational documents;

        (d) acquire or agree to acquire (i) by merging or consolidating with, or
by purchasing a substantial portion of the assets or stock of, or by any other
manner, any business or any person or (ii) except as set forth on Schedule
6.1(d) and as otherwise provided in Section 6.1(g), any assets except for the
purchase of assets for an amount which does not exceed, individually or in the
aggregate, $100,000;

        (e) except as set forth in Schedule 6.1(e), sell, lease, license,
mortgage or otherwise encumber or subject to any Lien or otherwise dispose of
any of its properties or assets, except sales of inventory or sales of
immaterial assets;




                                       25








<PAGE>

        (f) (i) except as set forth in Schedule 6.1(f), incur any indebtedness
(other than pursuant to existing credit agreements) or guarantee any such
indebtedness of another person, issue or sell any debt securities or warrants or
other rights to acquire any debt securities of the Company or any Subsidiary,
guarantee any debt securities of another person, enter into any "keep well" or
other agreement to maintain any financial statement condition of another person
or enter into any arrangement having the economic effect of any of the foregoing
except for short- term borrowings incurred in the ordinary course of business
consistent with past practice, or (ii) make any loans, advances or capital
contributions to, or investments in, any other person;

        (g) except for the items listed on Schedule 6.1(g), make or agree to
make any capital expenditure or expenditures with respect to property, plant or
equipment which, individually, is in excess of $75,000 or, in the aggregate, are
in excess of $250,000;

        (h) except as set forth on Schedule 6.1(h) or as required by law or as
consistent with past practice, make any material tax election or settle or
compromise any material income tax liability or take any action or position that
is inconsistent with the past tax or accounting practices of the Company;

        (i) except as set forth in Schedule 6.1(i) pay, discharge, settle or
satisfy any claims, liabilities or obligations (absolute, accrued, asserted or
unasserted, contingent or otherwise), other than the payment, discharge or
satisfaction, in the ordinary course of business consistent with past practice
or in accordance with their terms, of liabilities reflected or reserved against
in the most recent consolidated financial statements (or the notes thereto) of
the Company included in the Filed SEC Documents or incurred thereafter in the
ordinary course of business consistent with past practice, or waive any material
benefits of, or agree to modify in any material respect, any confidentiality,
standstill or similar agreements to which the Company or any Subsidiary is a
party;

        (j) except in the ordinary course of business consistent with past
practice, modify, amend or terminate any Commitment to which the Company or any
Subsidiary is a party, or waive, release or assign any rights or claims;

        (k) enter into any Commitment relating to the distribution, sale or
marketing by third parties of the Company's or any Subsidiary's products or
services or enter into any contract, agreement or other commitment with any
supplier to the Company unless such contract, agreement or other commitment is
terminable upon no more than thirty (30) days notice;

        (l) except as required to comply with applicable law and except as set
forth on Schedule 6.1(1), (i) adopt, enter into, terminate or amend any Benefit
Plan or other arrangement for the benefit or welfare of any director, officer or
current or former employee, (ii) increase in any manner the compensation or
fringe benefits of, or pay any bonus to, any director, officer or employee
(except for normal increases or bonuses in the ordinary course of business
consistent with past practice), (iii) pay any benefit not provided for under any
Benefit Plan (except for bonuses in the ordinary course of business consistent
with past practice), (iv) except as permitted in clause (ii), grant any awards
under any bonus, incentive, performance or other compensation plan or
arrangement or Benefit Plan (including the grant of stock options, stock
appreciation





                                       26








<PAGE>

rights, stock based or stock related awards, performance units or restricted
stock, or the removal of existing restrictions in any Benefit Plans or agreement
or awards made thereunder) or (v) take any action other than in the ordinary
course of business to fund or in any other way secure the payment of
compensation or benefits under any employee plan, agreement, contract or
arrangement or Benefit Plan; or

        (m) authorize any of, or commit or agree to take any of, the foregoing
actions.

6.2      No Solicitation.

        (a) The Company shall, shall cause each Subsidiary to and shall direct
and use reasonable efforts to cause its and its Subsidiaries' officers,
directors, employees, representatives and agents to, immediately cease any
discussions or negotiations with any parties other than Parent and Sub that may
be ongoing with respect to an Alternative Transaction (as hereinafter defined).
The Company shall not, shall cause each Subsidiary not to and shall not
authorize or permit any of its or its Subsidiaries' officers, directors or
employees or any investment banker, financial advisor, attorney, accountant or
other representative retained by it to, directly or indirectly, (i) solicit,
initiate or furnish any information in response to any inquiries or the making
of any proposal that may lead to an Alternative Transaction or (ii) participate
in any discussions or negotiations regarding any proposed Alternative
Transaction; provided, however, that if, at any time prior to the acceptance for
payment of Shares pursuant to and subject to the conditions (including the
Minimum Condition) of the Offer, the Board of Directors of the Company
determines in good faith, after consultation with its outside counsel, that
action is required by reason of the Board of Directors' fiduciary duties under
applicable law, the Company may (subject to compliance with Section 6.2(c)), in
response to an unsolicited Third Party Proposal (as defined herein), (A) furnish
information with respect to the Company to the person making such Third Party
Proposal pursuant to a confidentiality agreement that is at least as protective
of the Company's interests as is the Confidentiality Agreement (as defined in
Section 7.2) and (B) participate in negotiations regarding such Alternative
Transaction; provided, further, that nothing contained in this Agreement shall
prevent the Company or its Board of Directors from complying with Rules 14d-9
and 14e-2 promulgated under the Exchange Act with regard to any proposed
Alternative Transaction or withdrawing its recommendation of the Offer pursuant
to Section 6.2(b). Without limiting the foregoing, it is understood that any
violation of the restrictions set forth in the preceding sentence by any
director, officer or employee of the Company or any Subsidiary or any investment
banker, financial advisor, attorney, accountant or other representative of the
Company, acting on behalf of the Company, shall be deemed to be a breach of this
Section 6.2(a) by the Company. For purposes of this Agreement, a "Third Party
Proposal" means a bona fide proposal from a third party, which proposal did not
result from a breach of this Section 6.2(a) and which third party the Board of
Directors of the Company determines in good faith (after consultation with AH&H
or another financial advisor of nationally recognized reputation) to be
reasonably capable of completing a Superior Proposal (as defined in Section
9.1(d)). For purposes of this Agreement, an "Alternative Transaction" means any
direct or indirect acquisition or purchase of assets of the Company and its
Subsidiaries, taken as a whole, outside the ordinary course of business or
outstanding equity securities of the Company or any Subsidiary, any tender offer
or exchange offer that if consummated would result in any person





                                       27








<PAGE>

beneficially owning equity securities of the Company or any merger,
consolidation, business combination, sale of substantially all the assets,
recapitalization, liquidation, dissolution or similar transaction that would
result in the acquisition of the Company or any Subsidiary, other than the
transactions contemplated by this Agreement and other than the acquisition of
Shares pursuant to the exercise of Company Stock Options or Warrants which are
issued and outstanding as of the date hereof.

        (b) Neither the Board of Directors of the Company nor any Committee
thereof shall (i) withdraw or modify, or propose to withdraw or modify, the
approval or recommendation by such Board of Directors or such committee of the
Offer, this Agreement or the Merger, (ii) approve or recommend, or propose to
approve or recommend, any Alternative Transaction or (iii) cause the Company to
enter into any letter of intent, agreement in principle, acquisition agreement
or other agreement (an "Acquisition Agreement") with respect to an Alternative
Transaction unless in connection with the taking of any such action described in
Clause (i), (ii) or (iii) of this Section 6.2(b), the Board of Directors of the
Company shall have previously terminated this Agreement pursuant to Section
9.1(d). Notwithstanding the preceding sentence, if the Company's Board
determines in its good faith judgment, after taking into consideration the
advice of its outside legal counsel, that it is required by reason of their
fiduciary duties under applicable law, the Company's Board of Directors may
subject to Section 9.1(d): (A) withdraw its recommendation of the Offer or the
Merger and the other transactions contemplated hereby, or (B) approve or
recommend or cause the Company to enter into an agreement with respect to a
Superior Proposal; provided, however, that the Company concurrently terminates
this Agreement pursuant to Section 9.1(d).

        (c) In addition to the obligations of the Company set forth in
paragraphs (a) and (b) of this Section 6.2, the Company as promptly as
reasonably practicable shall advise Parent orally and in writing of any request
for information or of any proposal or any inquiry regarding any Alternative
Transaction and the material terms and conditions of such request, proposal or
inquiry. The Company will, to the extent reasonably practicable and not in
violation of the Board of Director's fiduciary duties under applicable law,
after consultation with its outside counsel, keep Parent fully informed of the
status and details (including amendments or proposed amendments) of any such
request, proposal or inquiry.

        (d) Nothing contained in this Section 6.2 shall prohibit the Company
from at any time taking and disclosing to its stockholders a position
contemplated by Rule 14e-2(a) promulgated under the Exchange Act or from making
any disclosure to the Company's stockholders, in each case with respect to any
Third Party Proposal, if (i) in the good faith judgment of the Board of
Directors of the Company, after consultation with its outside counsel, such
disclosure is required by reason of the Board of Directors' fiduciary duties
under applicable law and (ii) the Company shall have provided Parent and Sub
with reasonable advance notice of its position and proposed disclosure under the
circumstances; provided, however, that neither the Company nor its Board of
Directors nor any committee thereof shall, except as permitted by Section
6.2(b), withdraw or modify, or propose to withdraw or modify, its position with
respect to the Offer, the Merger or this Agreement or approve or recommend, or
propose to approve or recommend, an Alternative Transaction.





                                       28









<PAGE>

6.3     Certain Tax Matters.

        (a) From the date hereof until the Effective Time, (i) the Company and
each Subsidiary will file all tax returns and reports ("Post-Signing Returns")
required to be filed; (ii) the Company and each Subsidiary will timely pay all
taxes shown as due and payable on the Company's Post-Signing Returns that are so
filed; (iii) the Company and each Subsidiary will make provision for all taxes
payable by the Company for which no Post-Signing Return is due prior to the
Effective Time; and (iv) the Company will promptly notify Parent of any action,
suit, proceeding, claim or audit pending against or with respect to the Company
and each Subsidiary in respect of any tax where there is a reasonable
possibility of a determination or decision which would reasonably be expected to
have a material adverse effect on the Company's or any Subsidiary's tax
liabilities or tax attributes.

        (b) The Company shall use its best efforts to obtain from all its
employees who exercised a Company Stock Option or Warrants for which the proper
amount of payroll or employment taxes were not withheld by the Company upon the
exercise of such Company Stock Option or Warrant, a properly executed IRS Form
4669 from each such employee, in which such employee certifies that such
employee has paid in full all taxes applicable to the compensation income
attributable to such exercise.

6.4     Other Actions.

        The Company shall not, and shall cause each Subsidiary not to, take or
omit to take any action, the taking or omission of which would reasonably be
expected to result in (a) any of the representations and warranties of the
Company set forth in this Agreement becoming untrue or inaccurate in any
material respect or (b) any of the Offer Conditions not being satisfied (subject
to the Company's right to take actions specifically permitted by Section 6.2 or
9.1). For purposes of this Section 6.4, "in any material respect" shall mean
that claims, demands, damages, liabilities and losses arising out of such
untruth or inaccuracy will actually or may reasonably be expected to result in
damages, losses, costs and expenses (including reasonable attorney's fees and
court costs) (collectively, "Losses") suffered or incurred by the Company,
Parent or Sub, when taken as a whole, in excess of $300,000.

6.5     Advice of Changes; Filings.

      The Company shall confer with Parent on a regular and frequent basis as
reasonably requested by Parent, report on operational matters and promptly
advise Parent orally and, if requested by Parent, in writing of any material
change with respect to the Company or any Subsidiary. The Company shall promptly
provide to Parent (or its counsel) copies of all filings made by the Company or
any Subsidiary with any Governmental Entity in connection with this Agreement
and the transactions contemplated hereby.




                                       29










<PAGE>

6.6     Financial Information.

        The Company shall furnish to Parent the following financial information
(all to be prepared in accordance with generally accepted accounting principles
consistently applied):

        (a) as soon as available but in any event within 20 days of each
calendar month, the unaudited consolidated balance sheets, income statements and
cash flow statements of the Company, showing its financial condition as of the
close of such month and the results of operations during such month and for the
then elapsed portion of the Company's fiscal year, in each case, setting forth
the comparative figures for the corresponding month in the prior fiscal year and
the corresponding elapsed portion of the prior fiscal year; and

        (b) all documents filed with or submitted to the SEC by the Company
simultaneously with such filing or submission.

6.7     Employee Benefits

        Following the Closing Date, Parent may, at its option, continue the
employee benefits programs for employees of the Company as reflected on Schedule
4.15(a) annexed hereto, or, alternatively, include such employees in Parent's or
one of its Affiliate's employee benefits programs. In such connection, Parent
agrees that for purposes of any length of service requirements, waiting periods,
vesting periods or differential benefits based on length of service in any such
benefit programs, each such employee's service with the Company shall be deemed
to have been service with Parent or such Affiliate of Parent.

                                   ARTICLE VII

                              ADDITIONAL AGREEMENTS

7.1     Stockholder Approval; Preparation of Proxy Statement.

        (a) If the Company Stockholder Approval is required by law to consummate
the Merger, the Company will, as soon as practicable following the consummation
of the Offer, duly call, give notice of, convene and hold a meeting of its
stockholders (the "Stockholders Meeting") for the purpose of obtaining the
Company Stockholder Approval. The Company will, through its Board of Directors,
and subject to such board's fiduciary duties under applicable law after
consultation with its outside counsel, recommend to its stockholders that the
Company Stockholder Approval be given. Notwithstanding the foregoing, if Sub or
any other subsidiary of Parent shall acquire at least 90% of the outstanding
Shares, the parties shall, at the request of Parent, take all necessary and
appropriate action to cause the Merger to become effective as soon as
practicable after the consummation of the Offer without a Stockholders Meeting
in accordance with Section 82 of the MBCL.






                                       30









<PAGE>

        (b) If the Company Stockholder Approval is required by law to consummate
the Merger, the Company will, at Parent's request, as soon as practicable
following consummation of the Offer, prepare and file a preliminary Proxy
Statement with the SEC and will use its best efforts to respond to any comments
of the SEC or its staff and to cause the Proxy Statement to be mailed to the
Company's stockholders as promptly as practicable after responding to all such
comments to the satisfaction of the staff. The Company will notify Parent
promptly of the receipt of any comments from the SEC or its staff and of any
request by the SEC or its staff for amendments or supplements to the Proxy
Statement or for additional information and will supply Parent with copies of
all correspondence between the Company or any of its representatives, on the one
hand, and the SEC or its staff, on the other hand, with respect to the Proxy
Statement or the Merger. If at any time prior to the Stockholders Meeting there
shall occur any event that should be set forth in an amendment or supplement to
the Proxy Statement, the Company will promptly prepare and mail to its
stockholders such an amendment or supplement. The Company will not mail any
Proxy Statement, or any amendment or supplement thereto, to which Parent
reasonably objects, unless required by law, rule, regulation or the SEC staff,
in the opinion of outside counsel; provided, that Parent shall identify its
objections and fully cooperate with the Company to create a mutually
satisfactory Proxy Statement. In connection with such preliminary proxy
statement, Proxy Statement and any amendment or supplement thereto, Parent and
Sub should promptly provide all information reasonably requested by the Company.

        (c) Following the purchase of Shares, if any, pursuant to the Offer,
Parent shall ensure that all such Shares purchased continue to be held by
Parent, Sub, and/or a direct or indirect wholly-owned subsidiary of Parent until
such time as the Merger is consummated. At the Stockholders Meeting, Parent
agrees to cause all Shares purchased pursuant to the Offer and all other Shares
owned by Parent or any subsidiary of Parent to be voted in favor of the Company
Stockholder Approval.

7.2     Access to Information; Confidentiality.

        Upon reasonable notice, and except as may otherwise be required by
applicable law, the Company and its Subsidiaries shall afford to Parent, and to
Parent's officers, employees, accountants, counsel, financial advisers and other
representatives, reasonable access during normal business hours from the date
hereof to the Effective Time to all their respective properties, books,
contracts, commitments, personnel and records and, during such period, the
Company shall furnish promptly to Parent (a) a copy of each report, schedule,
registration statement and other document filed by it during such period
pursuant to the requirements of Federal or state securities laws and (b) all
other information concerning its business, properties and personnel as Parent
may reasonably request. Except as required by law, Parent will hold, and will
cause its officers, employees, accountants, counsel, financial advisers and
other representatives and Affiliates to hold, any and all information received
from the Company, directly or indirectly, in confidence, according to the terms
of the confidentiality agreement dated as of January 11, 1999, between the
Company and Parent (the "Confidentiality Agreement").




                                       31








<PAGE>

7.3     Reasonable Efforts; Notification.

        (a) Upon the terms and subject to the conditions set forth in this
Agreement, each of the parties agrees to use all reasonable efforts to take, or
cause to be taken, all actions, and to do, or cause to be done, and to assist
and cooperate with the other parties in doing, all things necessary, proper or
advisable to consummate and make effective, in the most expeditious manner
practicable, the Offer and the Merger, and the other transactions contemplated
by this Agreement, including (i) the obtaining of all necessary actions or
nonactions, waivers, consents and approvals from Governmental Entities and the
making of all necessary registrations and filings (including filings with
Governmental Entities, if any) and the taking of all reasonable steps as may be
necessary to obtain an approval or waiver from, or to avoid an action or
proceeding by, any Governmental Entity, (ii) the obtaining of all necessary
consents, approvals or waivers from third parties, (iii) the defending of any
lawsuits or other legal proceedings, whether judicial or administrative,
challenging this Agreement or the consummation of any of the transactions
contemplated by this Agreement, including seeking to have any stay or temporary
restraining order entered by any court or other Governmental Entity vacated or
reversed, and (iv) the execution and delivery of any additional instruments
necessary to consummate the transactions contemplated by, and to fully carry out
the purposes of, this Agreement. In connection with and without limiting the
foregoing, the Company and its Board of Directors shall (i) take all action
necessary to ensure that no state takeover statute or similar statute or
regulation is or becomes applicable to the Offer, the Merger, this Agreement,
the Stockholder Agreement or any of the other transactions contemplated by this
Agreement or the Stockholder Agreement and (ii) if any state takeover statute or
similar statute or regulation becomes applicable to the Offer, the Merger, this
Agreement, the Stockholder Agreement or any other transaction contemplated by
this Agreement or the Stockholder Agreement, take all action reasonably
necessary to ensure that the Offer, the Merger and the other transactions
contemplated by this Agreement may be consummated as promptly as practicable on
the terms contemplated by this Agreement and otherwise to minimize the effect of
such statute or regulation on the Offer, the Merger, this Agreement, the
Stockholder Agreement and the other transactions contemplated by this Agreement
or the Stockholder Agreement. Nothing in this Agreement shall be deemed to
require Parent to dispose of or hold separate any asset or collection of assets.

        (b) Each of the Company and Parent shall keep the other apprised of the
status of matters relating to completion of the transactions contemplated by
this Agreement, including promptly furnishing the other with copies of notices
or other communications received by Parent or the Company, as the case may be,
or their respective Subsidiaries, from any third party and/or any Governmental
Entity alleging that the consent of such third party or Governmental Entity is
or may be required with respect to the Offer, the Merger and the other
transactions contemplated by this Agreement. Each of the Company and Parent
shall give prompt notice to the other of (i) the occurrence or non-occurrence of
any fact or event which would be reasonably likely (x) to cause any
representation or warranty contained in this Agreement to be untrue or
inaccurate at any time from the date hereof to the Effective Time or (y) to
cause any covenant, condition or agreement under this Agreement not to be
complied with or satisfied and (ii) any failure of the Company,




                                       32








<PAGE>

Parent or Sub, as the case may be, to comply with or satisfy any covenant,
condition or agreement to be complied with or satisfied by it hereunder;
provided, however, that no such notification shall affect the representations,
warranties, covenants or agreement of the parties or the conditions to the
obligations of the parties under this Agreement.

7.4     Stock Option Plans and Warrants; Employee Stock Purchase Plan.

        (a) As soon as practicable following the date hereof but in no event
later than the consummation of the Offer, the Company (or, if appropriate, the
Board of Directors of the Company or any committee administering the Stock
Option Plans (as defined below)) shall (including by adopting resolutions or
taking any other actions) take action so as to allow each outstanding option to
purchase Shares (a "Company Stock Option") heretofore granted under any stock
option, stock appreciation rights or stock purchase plan, program, arrangement,
agreement of the Company (collectively, the "Stock Option Plans") and each
outstanding warrant or other right to purchase Shares (a "Warrant") in each case
outstanding immediately prior to the date hereof: (A) to the extent then
exercisable, either (i) to be canceled immediately after consummation of the
Offer in exchange for an amount in cash, payable at the time of such
cancellation, equal to the product of (x) the number of Shares subject to such
Company Stock Option or Warrant immediately prior to the Effective Time and (y)
the excess, if any, of the price per Share to be paid in the Offer over the per
Share exercise price of such Company Stock Option or Warrant (the "Net Amount")
or (ii) to be converted immediately prior to the Effective Time into the right
solely to receive the Net Amount; provided, that no such cash payment has been
made or (B) to the extent not then exercisable, to be canceled immediately after
consummation of the Offer. The Company shall not make, or agree to make, any
payment of any kind to any holder of a Company Stock Option or a Warrant (except
for the payment described above) without the consent of Parent.

        (b) As soon as practicable following the date hereof, but in no event
later than the consummation of the Offer, the Company (or if appropriate, the
Board of Directors of the Company or any committee administering the Employee
Stock Purchase Plan (as hereinafter defined)) shall take action to terminate any
open purchase periods with respect to Company Common Stock under the Company
Employee Stock Purchase Plan (the "Employee Stock Purchase Plan") and to cease
payroll deductions for such purpose, so as to ensure that all shares of Company
Common Stock that have been subscribed for have been purchased, and that no
subscriptions to purchase such shares are outstanding as of the Effective Time.

        (c) All Stock Option Plans and the Employee Stock Purchase Plan shall be
terminated as of the Effective Time and the provisions in any other Benefit Plan
providing for the issuance, transfer or grant of any capital stock of the
Company or any interest in respect of any capital stock of the Company shall be
terminated as of the Effective Time. The Company shall ensure that following the
Effective Time, no holder of a Company Stock Option or Warrant nor any
participant in any Stock Option Plan or in the Employee Stock Purchase Plan
shall have any right thereunder to acquire any capital stock of the Company,
Parent or the Surviving Corporation.




                                       33









<PAGE>

        (d) The Surviving Corporation shall continue to be obligated to pay the
Net Amount to holders of any Company Stock Options or Warrants converted in
accordance with clause (y) of Section 7.4(a).

        (e) The Company shall pay its portion and withhold and deposit the
proper amount of all Federal and state payroll and employment taxes required to
be paid and withheld from the Net Amount.

7.5     Indemnification, Exculpation.

        (a) All rights to indemnification and exculpation (including the
advancement of expenses) from liabilities for acts or omissions occurring at or
prior to the Effective Time (including with respect to the transactions
contemplated by this Agreement) existing as of the date hereof in favor of the
current or former directors or officers of the Company as provided in its
Articles of Organization, its By-laws and the indemnification agreements set
forth in Schedule 7.5 shall be assumed by the Surviving Corporation in the
Merger, without further action, as of the Effective Time and shall survive the
Merger and shall continue in full force and effect without amendment,
modification or repeal in accordance with their terms; provided however, that if
any claims are asserted or made within such period, all rights to
indemnification (and to advancement of expenses) hereunder in respect of any
such claims shall continue, without diminution, until disposition of any and all
such claims.

        (b) The provisions of this Section 7.5 are intended to be for the
benefit of, and will be enforceable by, each indemnified party, his or her heirs
and his or her representatives.

7.6     Directors.

        Promptly upon the acceptance for payment of, and payment for, any Shares
by Sub pursuant to and subject to the conditions (including the Minimum
Condition) of the Offer, Sub shall be entitled to designate such number of
directors on the Board of Directors of the Company as will give Sub, subject to
compliance with Section 14(f) of the Exchange Act, a majority of such directors,
and the Company shall, at such time, cause Sub's designees to be so elected by
its existing Board of Directors. Subject to applicable law, the Company shall
take all action requested by Parent necessary to effect any such election,
including mailing to its stockholders the Information Statement containing the
information required by Section 14(f) of the Exchange Act and Rule 14f-1
promulgated thereunder, and the Company agrees to make such mailing with the
mailing of the Schedule 14D-9 (provided that Parent and Sub shall have provided
to the Company on a timely basis in writing all information required to be
included in the Information Statement and Schedule 14D-9 with respect to Sub's
designees). In connection with the foregoing, the Company will promptly, at the
option of Parent, either increase the size of the Company's Board of Directors
and/or obtain the resignation of such number of its current directors as is
necessary to enable Sub's designees to be elected or appointed to, and to
constitute a majority of, the Company's Board of Directors as provided above.





                                       34








<PAGE>

7.7     Fees and Expenses.

        (a) Except as provided below in this Section 7.7, all fees and expenses
incurred in connection with the Offer, the Merger, this Agreement and the
transactions contemplated by this Agreement shall be paid by the party incurring
such fees or expenses, whether or not the Offer or the Merger is consummated,
except that printing and mailing costs and expenses shall be paid by Parent or
Sub.

        (b) In the event that this Agreement is terminated (i) by Parent or Sub
pursuant to Section 9.1(c), (ii) by Parent pursuant to and in accordance with
Section 9.1(b)(i)(x) if such termination results from the failure of the Offer
Conditions described in paragraphs (c), (f) or (h) of Exhibit A as a result of
any breach by the Company of any covenant or agreement (including, without
limitation, the covenants set forth in Section 6.2(b)) or any representation or
warranty made by the Company in this Agreement or (iii) pursuant to Section
9.1(d), in each case, in lieu of any liability or obligation to pay damages, the
Company shall promptly pay to Parent in immediately available funds a
termination fee including all Expenses (as defined herein) equal to One Million
and No/100 Dollars ($1,000,000.00). The Company acknowledges that the agreements
contained in this Section 7.7(b) are an integral part of the transactions
contemplated by this Agreement, and that, without these agreements, Parent would
not enter into this Agreement. Accordingly, if the Company fails promptly to pay
the amount due pursuant to this Section 7.7(b), and, in order to obtain such
payment, Parent commences a suit which results in a judgment against the Company
for the fee set forth in this Section 7.7(b), the Company shall pay to Parent
all costs and expenses (including attorneys' fees and expenses) in connection
with such suit, together with interest on the amount of the fee at the prime
rate of Citibank in effect on the date such payment was required to be made. If
such a suit results in a judgment against Parent and/or Sub, Parent shall pay to
the Company all costs and expenses (including attorney's fees and expenses) in
connection with such suit. "Expenses" means all out-of-pocket expenses incurred
by Parent and Sub in connection with this Agreement, the Stockholder Agreement
and the transactions contemplated hereby and thereby, including fees and
expenses of its printer, consultants, attorneys, accountants, and other
advisors.

7.8     Public Announcements.

        Parent and Sub, on the one hand, and the Company, on the other hand,
will consult with each other before issuing, and provide each other the
opportunity to review and comment upon, any press release or other public
statements with respect to the transactions contemplated by this Agreement,
including the Offer and the Merger, and shall not issue any such press release
or make any such public statement prior to such consultation, except as may be
required by applicable law, court process or by obligations pursuant to any
listing agreement with any national securities exchange or national securities
quotation system. The parties agree that the initial press release to be issued
with respect to the transactions contemplated by this Agreement shall be in the
form heretofore agreed to by the parties.




                                       35








<PAGE>

7.9     Stop Transfer.

        The Company shall not register the transfer of any certificate
representing any Subject Shares (as defined in the Stockholder Agreement),
unless such transfer is made to Parent or Sub or otherwise in compliance with
the Stockholder Agreement. The Company will inscribe upon any certificates
representing Subject Shares tendered by a Stockholder (as defined in the
Stockholder Agreement) for such purpose the following legend: "THE SHARES OF
COMMON STOCK, $.01 PAR VALUE OF ENDOGEN, INC. REPRESENTED BY THIS CERTIFICATE
ARE SUBJECT TO A STOCKHOLDERS AGREEMENT DATED AS OF MAY 27, 1999 AND MAY NOT BE
SOLD OR OTHERWISE TRANSFERRED, EXCEPT IN ACCORDANCE THEREWITH. COPIES OF SUCH
AGREEMENT MAY BE OBTAINED AT THE PRINCIPAL EXECUTIVE OFFICES OF ENDOGEN, INC."

7.10    Sub Stock Option

        (a) Grant of Sub Stock Option. The Company hereby grants Sub an
irrevocable option (the "Sub Stock Option") to purchase up to 690,172 shares of
Company Common Stock (the "Sub Shares") at a price per share equal to the Offer
Price payable in cash.

        (b) Exercise of Sub Stock Option. The Sub Stock Option may be exercised,
in whole or in part, at any time and from time to time after the date on which
Sub has accepted for payment the Shares tendered pursuant to the Offer and
subject to satisfaction of the Minimum Condition if, but only if, Parent and Sub
agree to permanently waive the Offer Conditions; provided that there shall not
be in effect any preliminary or final injunction or other order issued by any
Government Entity prohibiting the issuance of the Sub Shares pursuant to this
Agreement. The Sub Stock Option shall expire upon the earlier of (i) the
Effective Time, or (ii) the date upon which this Agreement is terminated in
accordance with its terms. Sub may exercise the Sub Stock Option for all or some
of the Shares by sending written notice (the "Option Notice") to the Company
specifying the number of Sub Shares it will purchase pursuant to such exercise
and the price and date not less than five (5) nor more than twenty (20) days
from the date of the Option Notice for the closing of such purchase.

        (c) Closing. At any closing on the date specified under subsection (b)
of this Section 7.10, (i) Sub will make payment to the Company of the aggregate
price for the Sub Shares being purchased upon exercise of the Sub Stock Option
by wire transfer of immediately available funds to an account designated in
writing by the Company and (ii) the Company will deliver to the Sub a
certificate or certificates representing the number of shares of Company Common
Stock so purchased in the denominations designated by the Sub and receipt
evidencing payment of any requisite stock transfer taxes. At any such closing
Sub shall deliver a letter to the Company agreeing that the Sub will not offer
to sell, or otherwise dispose of, any Sub Shares acquired by it pursuant to the
Sub Stock Option in violation of the Securities Act and any applicable state
securities laws.




                                       36








<PAGE>

        (d) Adjustment. If any change in the Company Common Stock occurs by
reason of a stock dividend, split up, recapitalization, combination, exchange of
shares or the like, the number of Sub Shares and the purchase price per share
shall be adjusted appropriately.

        (e) Assignment of Sub Stock Option. Sub may assign this Sub Stock Option
to any of its Affiliates. Except for an assignment to an Affiliate of Sub, Sub
may not assign the Sub Stock Option without the prior written consent of the
Company.

        (f) Reservation of Sub Shares. The Company represents and warrants to
Parent and Sub that it has reserved such number of shares of Company Common
Stock as is necessary for issuance upon the exercise of the Sub Stock Option.

                                  ARTICLE VIII

                                   CONDITIONS

8.1     Conditions to Each Party's Obligation To Effect the Merger.

        The respective obligation of each party to effect the Merger shall be
subject to the prior satisfaction or waiver the following conditions:

        (a) Company Stockholder Approval. If required by applicable law, the
Company Stockholder Approval shall have been obtained; provided that Parent and
Sub shall vote all their Shares in favor of the Merger.

        (b) No Injunctions or Restraints. No statute, rule, regulation,
executive order, decree, temporary restraining order, preliminary or permanent
injunction or other order issued by any court of competent jurisdiction or other
Governmental Entity or other legal restraint or prohibition preventing the
consummation of the Merger shall be in effect; provided, however, that each of
the parties shall have used reasonable efforts to prevent the entry of any such
injunction or other order and to appeal as promptly as possible any injunction
or other order that may be entered.

        (c) Purchase of Shares. Sub shall have previously accepted for payment
and paid for Shares pursuant to and subject to the conditions (including the
Minimum Condition) of the Offer.




                                       37









<PAGE>



                                   ARTICLE IX
                            TERMINATION AND AMENDMENT

9.1     Termination.

        This Agreement may be terminated at any time prior to the Effective
Time, whether before or after approval of the terms of this Agreement by the
stockholders of the Company as follows:

(a)     By mutual written consent of Parent and the Company.

        (b) By either Parent or the Company: (i) if (x) as a result of the
failure of any of the Offer Conditions the Offer shall have terminated or
expired in accordance with its terms without Sub having accepted for payment
Shares pursuant to and subject to the Offer Conditions (including the Minimum
Condition) or (y) Sub shall not have accepted for payment Shares pursuant to the
Offer prior to July 31, 1999; and provided, further, that the right to terminate
this Agreement pursuant to this Section 9.1(b)(i) shall not be available to any
party whose failure to perform any of its obligations under this Agreement
proximately contributed to the failure of any such condition or if the failure
of such condition results from facts or circumstances that constitute a breach
of any representation or warranty under this Agreement by such party; or (ii) if
any Governmental Entity shall have issued an order, decree or ruling or taken
any other action permanently enjoining, restraining or otherwise prohibiting the
acceptance for payment of, or payment for, Shares pursuant to the Offer or the
Merger and such order, decree or ruling or other action shall have become final
and nonappealable.

        (c) By Parent or Sub prior to Sub's obligation to accept Shares for
payment pursuant to the Offer in the event of a material breach by the Company
of any representation, warranty, covenant or other agreement contained in this
Agreement which would or reasonably would be expected to give rise to the
failure of a condition set forth in Exhibit A. For purposes of this Section
9.1(c), "material breach" shall mean that claims, demands, damages, liabilities
and losses arising out of such breach will actually or may reasonably be
expected to result in Losses suffered or incurred by the Company, Parent or Sub,
when taken as a whole, in excess of $300,000.

        (d) By either Parent or the Company if, prior to the obligation of Sub
to accept Shares for payment pursuant to the Offer, the Company, after complying
with the procedures set forth in Section 6.2, (i) amends the Schedule 14D-9 or
takes other action to modify its recommendation that the Offer and the Merger
are fair to and in the best interest of the Company and its stockholders and its
recommendation that the Company's stockholders accept the Offer, tender their
shares pursuant to the Offer and approve and adopt the Merger and this Agreement
or (ii) enters into an Acquisition Agreement for an Alternative Transaction that
constitutes a Superior Proposal (as defined below). For purposes of this
Agreement, a "Superior Proposal" means any Third Party Proposal to acquire,
directly or indirectly all of the Shares or all or substantially all of the
assets of the Company; provided that (A) the Board of Directors of the Company





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<PAGE>

determines in its good faith judgment (after consulting with AH&H or another
financial advisor of nationally recognized reputation) that such Third Party
Proposal is on terms that are more favorable to the Company's stockholders from
a financial point of view than the Offer and the Merger (taking into account all
relevant factors, including the amount and form of consideration to be received
in respect of the Shares, the relative value of any non-cash consideration, and
the timing and certainty of closing), and (B) the Board of Directors of the
Company determines in its good faith judgment (after consultation with its
outside counsel) that the failure to recommend or accept such Third Party
Proposal would be required in order for its members to comply with their
fiduciary duties under applicable law.

        (e) By the Company, if Sub or Parent shall have (i) failed to commence
the Offer within five business days of the date hereof, (ii) failed to pay for
Shares pursuant to the Offer to the extent required by Section 1.1(a) hereof or
(iii) breached in any material respect any of their respective representations,
warranties, other covenants or other agreements contained in this Agreement,
which breach or failure to perform in respect of clause (iii) is incapable of
being cured or has not been cured within 30 days after the giving of written
notice to Parent or Sub, as applicable, except, in any case under clause (iii),
such breaches and failures which would not prevent the consummation of the Offer
or the Merger subject to the terms and conditions of this Agreement.

9.2     Effect of Termination.

        In the event of a termination of this Agreement by either the Company or
Parent as provided in Section 9.1, this Agreement shall forthwith become void
and there shall be no liability or obligation on the part of Parent, Sub or the
Company or their respective officers or directors, except with respect to the
last sentence of Section 1.2(c), Section 5.6, the last sentence of Section 7.2,
Section 7.7, Section 9.1, this Section 9.2 and Article X; provided, however,
that, except as set forth in Section 7.7, nothing herein shall relieve any party
for liability for any breach hereof.

9.3     Amendment.

        This Agreement may be amended by the parties hereto, by action taken or
authorized by their respective Boards of Directors, at any time before or after
obtaining the Company Stockholder Approval (if required by law), but, after any
such approval, no amendment shall be made which by law requires further approval
by such shareholders without obtaining such further approval. This Agreement may
not be amended except by an instrument in writing signed on behalf of each of
the parties hereto.

9.4      Extension; Waiver.

        At any time prior to the Effective Time, the parties hereto, by action
taken or authorized by their respective Boards of Directors, may, to the extent
legally allowed, (i) extend the time for






                                       39









<PAGE>

the performance of any of the obligations or other acts of the other parties
hereto, (ii) waive any inaccuracies in the representations and warranties
contained herein or in any document delivered pursuant hereto or (iii) subject
to Section 1.1(a) and Section 9.3, waive compliance with any of the agreements
or conditions contained herein. Any agreement on the part of a party hereto to
any such extension or waiver shall be valid only if set forth in a written
instrument signed on behalf of such party. The failure of any party to this
Agreement to assert any of its rights under this Agreement or otherwise shall
not constitute a waiver of those rights.

9.5     Procedure for Termination, Amendment, Extension or Waiver.

        A termination of this Agreement pursuant to Section 9.1, an amendment of
this Agreement pursuant to Section 9.3 or an extension or waiver pursuant to
Section 9.4 shall, in order to be effective, require in the case of Parent, Sub
or the Company, action by its Board of Directors or the duly authorized designee
of its Board of Directors; provided, however, that in the event that Sub's
designees are appointed or elected to the Board of Directors of the Company as
provided in Section 7.6, after the acceptance for payment and payment of Shares
pursuant to and subject to the Offer Conditions (including the Minimum
Condition) and prior to the Effective Time, the affirmative vote of a majority
of the directors of the Company that were not designated by Parent or Sub shall
be required by the Company to (i) amend or terminate this Agreement by the
Company, (ii) exercise or waive any of the Company's rights or remedies under
this Agreement, (iii) extend the time for performance of Parent's and Sub's
respective obligations under this Agreement or (iv) take any action to amend or
otherwise modify the Company's Articles of Organization or By-laws.

                                    ARTICLE X
                                  MISCELLANEOUS

10.1    Nonsurvival of Representations, Warranties and Agreements.

        None of the representations, warranties or covenants (subject to the
succeeding sentence) in this Agreement or in any instrument delivered pursuant
to this Agreement shall survive the Effective Time. This Section 10.1 shall not
limit any covenant or agreement of the parties which by its terms contemplates
performance after the Effective Time of the Merger, including Section 7.5.

10.2    Notices.

        All notices and other communications hereunder shall be in writing and
shall be deemed given if delivered personally, telecopied (which is confirmed),
sent by overnight courier (providing proof of delivery) or mailed by registered
or certified mail (return receipt requested) to the parties at the following
addresses (or at such other address for a party as shall be specified by like
notice):




                                       40








<PAGE>

if to Parent or Sub, to        c/o Pierce Chemical Company
                               3747 North Meridian Road
                               Rockford, Illinois 61101
                               Attention:  Robb Anderson, President
                               Telecopy No.: (815) 968-0410

with a copy to:                Wiggin & Dana
                               Three Stamford Plaza
                               Stamford, CT 06911
                               Attention: Patricia Kavee Melick, Esq.
                               Telecopy No.: (203) 363-7676

and, if to the Company, to     Endogen, Inc.
                               30 Commerce Way
                               Woburn, Massachusetts
                               Attention: Owen A. Dempsey
                               Telecopy No.: (781) 756-3280

with a copy to:                Testa, Hurwitz & Thibeault, LLP
                               High Street Tower
                               125 High Street
                               Boston, MA 02110
                               Attention: Brian Goldstein, Esq.
                               Telecopy No.: (617) 248-7100

10.3    Interpretation.

        When a reference is made in this Agreement to an Article or a Section,
such reference shall be to an Article or a Section of this Agreement unless
otherwise indicated. The table of contents and headings contained in this
Agreement are for reference purposes only and shall not affect in any way the
meaning or interpretation of this Agreement. Unless the context otherwise
requires, words importing the singular shall include the plural, and vice versa.
Whenever the words "include", "includes" or "including" are used in this
Agreement, they shall be deemed to be followed by the words "without
limitation". As used in this Agreement, the term "subsidiary" of any person
means another person, an amount of the voting securities, other voting ownership
or voting partnership interests of which is sufficient to elect at least a
majority of its Board of Directors or other governing body (or, if there are no
such voting interests, 50% or more of the equity interests of which) is owned
directly or indirectly by such first person. As used in this Agreement,
"material adverse effect" means, when used in respect of the Company, any effect
or condition that, individually or in the aggregate with any other effect or
condition, is materially adverse to the assets, properties, business, financial
condition, results of operations or prospects of the Company and its
Subsidiaries, taken as a whole and any occurrence that with notice or lapse of
time or both could reasonably be expected to result in any such effect or
condition. As used in this Agreement, "material adverse change" means, when used
in respect of the Company,






                                       41








<PAGE>

any change or event that, individually or in the aggregate with any other change
or event, is materially adverse to the assets, properties, business, financial
condition, results of operations or prospects of the Company and its
Subsidiaries, taken as a whole and any occurrence that with notice or lapse of
time or both could reasonably be expected to result in any such change or event.
As used in this Agreement, the phrase "knowledge" with respect to the Company,
means to the actual knowledge of the Company, its Subsidiaries, and each of
their respective directors and officers. As used in this Agreement, the term
"person" shall be interpreted broadly and shall include any person, individual,
corporation, limited partnership, limited liability company, trust, association
or other entity or business organization of any kind or division thereof.

10.4    Counterparts.

        This Agreement may be executed in two or more counterparts, all of which
shall be considered one and the same agreement and shall become effective when
two or more counterparts have been signed by each of the parties and delivered
to the other parties, it being understood that all parties need not sign the
same counterpart.

10.5    Entire Agreement; Third Party Beneficiaries.

        This Agreement (a) constitutes the entire agreement and supersedes all
prior agreements and understandings, both written and oral, among the parties
with respect to the subject matter hereof, and (b) except as provided in
Sections 6.7 and 7.5 are not intended to confer upon any person other than the
parties hereto any rights or remedies hereunder.

10.6    Governing Law.

        This Agreement shall be governed and construed in accordance with the
laws of the Commonwealth of Massachusetts.

10.7    Publicity.

        Except as otherwise required by law or the rules of the Nasdaq National
Market, for so long as this Agreement is in effect, neither the Company nor
Parent shall, or shall permit any of its subsidiaries to, issue or cause the
publication of any press release or other public announcement with respect to
the transactions contemplated by this Agreement without the consent of the other
party, which consent shall not be unreasonably withheld.

10.8    Assignment.

        Neither this Agreement nor any of the rights, interests or obligations
hereunder shall be assigned by any of the parties hereto (whether by operation
of law or otherwise) without the prior





                                       42









<PAGE>

written consent of the other parties. Subject to the preceding sentence, this
Agreement will be binding upon, inure to the benefit of Sub and be enforceable
by the parties and their respective successors and assigns; provided, however,
that Sub may assign its rights, interest or obligations hereunder to any other
subsidiary of Parent without first obtaining the Company's consent.

10.9    Enforcement.

        The parties agree that irreparable damage would occur in the event that
any of the provisions of this Agreement were not performed in accordance with
their specific terms or were otherwise breached. It is accordingly agreed that
the parties shall be entitled to an injunction or injunctions to prevent
breaches of this Agreement and to enforce specifically the terms and provisions
of this Agreement in any court, this being in addition to any other remedy to
which they are entitled at law or in equity.

10.10.  No Personal Liability

        This Agreement shall not create or be deemed to create any personal
liability or obligation on the part of any direct or indirect stockholder of the
Company or any Subsidiary of the Company, or any of their respective officers,
directors, employees, agents or representatives.


                            [signature page follows]


                                       43









<PAGE>


        IN WITNESS WHEREOF, Parent, Sub and the Company have caused this
Agreement to be signed by their respective officers thereunto duly authorized as
of the date first written above.

                               PERBIO SCIENCE AB



                               By: /s/ Magnus Lindquist
                                  ___________________________________________
                                  Name: Magnus Lindquist
                                  Title: Director, PerBio Science AB
                                         Chief Financial Officer, Perstorp AB



                               By: /s/ Mats Fischier
                                  ______________________________________________
                                  Name: Mats Fischier
                                  Title: Director, PerBio Science AB
                                  Chief Executive Officer, Perstorp Life Science


                               EWOK ACQUISITION CORP.



                               By: /s/ Robb Anderson
                                  ______________________________________________
                                  Name:  Robb Anderson
                                  Title: President



                               By: /s/ Charles Granneman
                                  ______________________________________________
                                  Name:  Charles Granneman
                                  Title: Treasurer


                               ENDOGEN, INC.



                               By: /s/ Owen A. Dempsey
                                  ______________________________________________
                                  Name:  Owen A. Dempsey
                                  Title: President



                               By: /s/ Avery W. Catlin
                                  ______________________________________________
                                  Name:  Avery W. Catlin
                                  Title: Treasurer




                                       44









<PAGE>




                                    EXHIBIT A

                             CONDITIONS OF THE OFFER

        Notwithstanding any other term of the Offer, Sub shall not be required
to accept for payment or, subject to any applicable rules and regulations of the
SEC, including Rule 14e-1(c) under the Exchange Act (relating to Sub's
obligation to pay for or return tendered Shares after the termination or
withdrawal of the Offer), to pay for any Shares tendered pursuant to the Offer
unless there shall have been validly tendered and not withdrawn prior to the
expiration of the Offer such number of Shares that together with Shares subject
to the Stockholder Agreement that shall not have been tendered would constitute
two-thirds of the Shares on a fully-diluted basis (the "Minimum Condition").

        Furthermore, notwithstanding any other term of the Offer, Sub shall not
be required to accept for payment or, subject as aforesaid, to pay for any
Shares not theretofore accepted for payment or paid for, and, except as
otherwise provided in this Agreement or under applicable law, may terminate the
Offer if, at any time after the date hereof and before the acceptance of such
Shares for payment or the payment therefor, any of the following conditions
exists and be continuing as of any Expiration Date (other than as a result of
any action or inaction of Parent or any of its subsidiaries that constitutes a
breach of this Agreement):

        (a) there shall be instituted or pending by any person or Governmental
Entity any suit, action or proceeding (i) challenging the acquisition by Parent
or Sub of any Shares under the Offer or pursuant to the Stockholder Agreement,
seeking to restrain or prohibit the making or consummation of the Offer or the
Merger or the performance of any of the other transactions contemplated by this
Agreement or the Stockholder Agreement (including the voting provision
thereunder), or seeking to obtain from the Company, Parent or Sub any damages in
connection with the aforesaid transactions that are material in relation to the
Company, (ii) seeking to compel the Parent to dispose of or hold separate any
material portion of the business or assets of the Company, or Parent and its
subsidiaries, taken as a whole, as a result of the Offer (iii) seeking to impose
material limitations on the ability of Parent or Sub to acquire or hold, or
exercise full rights of ownership of, any Shares to be accepted for payment
pursuant to the Offer or purchased under the Stockholder Agreement including,
without limitation, the right to vote such Shares on all matters properly
presented to the stockholders of the Company, or (iv) seeking to prohibit Parent
or any of its subsidiaries from effectively controlling in any material respect
any material portion of the assets, properties, business or operations of the
Company and its Subsidiaries, taken as a whole;

        (b) there shall be any statute, rule, regulation, judgment, order,
injunction or other restraint enacted, entered, enforced, promulgated or deemed
applicable to the Offer or the Merger, or any other action shall be taken by any
Governmental Entity or court that is reasonably likely to result, directly or
indirectly, in any of the consequences referred to in clauses (i) through (iv)
of paragraph (a) above; provided, however, that each of Parent and Sub shall
have used reasonable efforts to prevent the entry of any such injunction or
other court order and to appeal as promptly as possible any injunction or other
court order that may be entered;








<PAGE>

        (c) there shall have occurred and continue to exist as of any Expiration
Date any material adverse change;

        (d) there shall have occurred and continue to exist as of any Expiration
Date (i) any general suspension of trading in, or limitation on prices for,
securities on the New York Stock Exchange or the NASDAQ, (ii) a declaration of a
banking moratorium or any suspension of payments in respect of banks in the
United States or any limitation by federal or state authorities on the extension
of credit by lending institutions, or a disruption of or other event materially
adversely affecting the extension of credit by lending institutions, (iii) a
commencement of a war or armed hostilities or other national or international
calamity directly or indirectly involving the United States, which has and
continues to materially adversely affect the trading of securities on the NYSE
involving the United States or (iv) in the case of any of the foregoing existing
at the time of the commencement of the Offer, a material acceleration or
worsening thereof;

        (e) the representations and warranties of the Company set forth in this
Agreement shall not be true and correct at the date hereof and at the scheduled
or extended Expiration Date of the Offer as though made on or as of such date
(except for representations and warranties made as of a specified date) but only
if the respects in which the representations and warranties made by the Company
are inaccurate would in the aggregate have a Company material adverse effect and
if such breaches of representations or warranties have not been cured within
five (5) business days of written notice to Company by Parent or Sub; provided,
however that in no event shall Parent be obligated to extend the Offer for more
than one five (5) business-day extension pursuant to Section 1.1(a)(A) or beyond
July 1, 1999 in order to permit Company to cure any such breach. For purposes of
this Offer Condition, "material adverse effect" shall mean that claims, demands,
liabilities and losses arising out of such inaccuracy will actually or may
reasonably be expected to result in Losses suffered or incurred by the Company,
Parent or Sub, when taken as a whole, in excess of $300,000.

        (f) the Company shall have failed to perform in any material respect any
obligation or to comply in any material respect with any agreement or covenant
of the Company to be performed or complied with by it under this Agreement and
such failure has a material adverse effect;

        (g) this Agreement shall have been terminated in accordance with its
terms; or

        (h) the Company's total stockholders equity as of May 31, 1999 shall not
be at least Five Million Five Hundred Thousand No/100 Dollars ($5,500,000.00) as
determined in accordance with Company's past practice consistently applied;

which in the reasonable judgment of Parent, in any such case, makes it
inadvisable to proceed with the Offer or the acceptance for payment or payment
for the Shares.

        The foregoing conditions, other than conditions (b) and (g), are for the
sole benefit of Sub and Parent and may, subject to the terms of this Agreement,
be waived by Sub and Parent in whole or in part at any time and from time to
time in their sole discretion. The failure by Parent or Sub at any time to
exercise any of the foregoing rights shall not be deemed a waiver of any such
right, the waiver of any such right with respect to particular facts and
circumstances shall



                                       2








<PAGE>

not be deemed a waiver with respect to any other facts and circumstances and
each such right shall be deemed an ongoing right that may be asserted at any
time and from time to time, except as otherwise provided in this Agreement.






                                       3









<PAGE>



                                                   May 27, 1999

Endogen, Inc.
30 Commerce Way
Woburn, MA  01801

Gentlemen:

        This letter confirms certain understandings with respect to the
Agreement and Plan of Merger (the "Merger Agreement") dated as of even date
herewith by and among PerBio Science AB, a Swedish corporation ("Parent"), EWOK
Acquisition Corp., a Massachusetts corporation ("Sub") and Endogen, Inc., a
Massachusetts corporation (the "Company"). Each capitalized term used herein and
not otherwise defined shall have the meaning ascribed to it in the Merger
Agreement.

        For the purposes of paragraph (a) to Exhibit A of the Merger Agreement,
the phrase "on a fully diluted basis" shall be defined to exclude the following:

        1.     All outstanding stock options issued pursuant to the Company's
               1992 Stock Plan that are irrevocably terminated, consistent with
               Section 7.4(a)(A)(i) or (B) of the Merger Agreement, effective as
               of the time that Sub accepts for payment, and pays for, all
               Shares tendered and not withdrawn pursuant to the Offer;

        2.     All outstanding options issued pursuant to the Company's 1993
               Non-Employee Director Stock Option Plan that are irrevocably
               terminated by the holders of those options, effective as of the
               time that Sub accepts for payment, and pays for, all Shares
               tendered and not withdrawn pursuant to the Offer;

        3.     A certain warrant to purchase 125,000 shares of common stock of
               the Company held by Third Wave Technologies, Inc.; provided that
               such warrant is irrevocably terminated by the holder thereof,
               effective as of the time that Sub accepts for payment, and pays
               for, all Shares tendered and not withdrawn pursuant to the Offer.

                                                   Sincerely yours,

                                                   PERBIO SCIENCE AB

                                                   By: /s/ Magnus Lindquist
                                                       -------------------------
                                                   Name:  Magnus Lindquist
                                                   Title: Director

                                                   EWOK ACQUISITION CORP.

                                                   By: /s/ Robb Anderson
                                                       -------------------------
                                                   Name:  Robb Anderson
                                                   Title: President

Accepted and agreed to:

ENDOGEN, INC.

By: /s/ Owen A. Dempsey
   ---------------------
Name:  Owen A. Dempsey
Title: President










<PAGE>


                              STOCKHOLDER AGREEMENT

        STOCKHOLDER AGREEMENT, dated as of May 27, 1999 (this "Agreement") among
PERBIO SCIENCE AB, a Swedish corporation, ("Parent"), EWOK ACQUISITION CORP., a
Massachusetts corporation and a wholly owned subsidiary of Parent ("Sub") and
the individuals listed on Schedule A attached hereto (each, a "Stockholder" and,
collectively, the "Stockholders").

        WHEREAS, Parent, Sub, and Endogen, Inc. (the "Company") propose to enter
into an Agreement and Plan of Merger dated as of the date hereof (as the same
may be amended or supplemented, the "Merger Agreement") providing for (i) the
making of a cash tender offer (as such offer may be amended from time to time as
permitted under the Merger Agreement, the "Offer") by Sub for all the
outstanding shares of common stock, par value $.01 per share, of the Company
("Company Common Stock") and (ii) for the merger of Sub with and into the
Company (the "Merger"), upon the terms and subject to the conditions set forth
in the Merger Agreement; and

        WHEREAS, each Stockholder owns the number of shares of Company Common
Stock set forth opposite his or its name on Schedule A attached hereto (such
shares of Company Common Stock, together with any other shares of capital stock
of the Company acquired by such Stockholders after the date hereof and during
the term of this Agreement (including, without limitation, through the exercise
of any stock options, warrants or similar instruments), being collectively
referred to herein as the "Subject Shares"); and

        WHEREAS, as a condition to its willingness to enter into the Merger
Agreement, Parent has requested that each Stockholder enter into this Agreement;

        NOW, THEREFORE, to induce Parent to enter into, and in consideration of
its entering into, the Merger Agreement, and in consideration of the premises
and the representations, warranties and agreements contained herein, the parties
agree as follows (capitalized terms used herein but not defined herein have the
meanings set forth in the Merger Agreement):

1.      REPRESENTATIONS AND WARRANTIES OF EACH STOCKHOLDER.

        Each Stockholder hereby represents and warrants, severally and not
jointly, to Parent as of the date hereof in respect of himself or itself as
follows:

        (a) Authority. The Stockholder has all requisite power and authority to
enter into this Agreement and to consummate the transactions contemplated
hereby. The execution, delivery and performance of this Agreement by the
Stockholder, and the consummation of the transactions contemplated hereby, have
been duly authorized by all necessary action on the part of the Stockholder.
This Agreement has been duly executed and delivered by the Stockholder and
constitutes a valid and binding obligation of the Stockholder enforceable
against the Stockholder in accordance with its terms. Except for the
informational filings with the SEC, the










<PAGE>

execution and delivery of this Agreement do not, and the consummation of the
transactions contemplated hereby and compliance with the terms hereof will not,
(i) conflict with, or result in any violation of, or default (with or without
notice or lapse of time or both) under any provision of, any certificate or
articles of incorporation, bylaws, certificate or articles of limited
partnership, limited partnership agreement, trust agreement, loan or credit
agreement, note, bond, mortgage, indenture, lease or other agreement,
instrument, permit, concession, franchise, license, judgment, order, notice,
decree, statute, law, ordinance, rule or regulation applicable to the
Stockholder or to the Stockholder's property or assets, including the Subject
Shares, (ii) require any filing with, or permit, authorization, consent or
approval of, or notice to, any federal, state or local government or any court,
tribunal, administrative agency or commission or other governmental or
regulatory authority or agency, domestic, foreign or supranational, or (iii)
violate any order, writ, injunction, decree, statute, rule or regulation
applicable to the Stockholder or any of the Stockholder's properties or assets,
including the Subject Shares. If the Stockholder is a natural person and is
married, and the Stockholder's Subject Shares constitute community property or
otherwise need spousal or other approval for this Agreement to be legal, valid
and binding, this Agreement has been duly authorized, executed and delivered by,
and constitutes a valid and binding agreement of, the Stockholder's spouse,
enforceable against such spouse in accordance with its terms, except as such
enforceability may be limited by applicable bankruptcy laws or creditors' rights
generally or by general principles of equity. No trust of which such Stockholder
is a trustee requires the consent of any beneficiary to the execution and
delivery of this Agreement or to the consummation of the transactions
contemplated hereby.

        (b) The Subject Shares. The Stockholder is the record and beneficial
owner of, and has good and marketable title to, the Subject Shares set forth
opposite his or its name on Schedule A attached hereto, free and clear of any
Liens. The Stockholder does not own, of record or beneficially, any shares of
capital stock of the Company or any Subsidiary other than the Subject Shares set
forth opposite his or its name on Schedule A attached hereto. The Stockholder
has the sole right to vote such Subject Shares, and none of such Subject Shares
is subject to any voting trust or other agreement, arrangement or restriction
with respect to the voting of such Subject Shares, except as contemplated by
this Agreement.

        (c) Brokers. No broker, finder, investment banker or other person is
entitled to any brokerage, finder's or other fee or commission in connection
with the execution of this Agreement by such Stockholder or the performance by
such Stockholder of its obligations hereunder (it being understood that Adams,
Harkness & Hill, Inc. and others disclosed to Sub pursuant to the Merger
Agreement may be entitled to certain fees and expenses in connection with the
transactions contemplated by the Merger Agreement, which fees and expenses shall
be paid by the Company as set forth in the Merger Agreement).

2.      PURCHASE AND SALE OF SHARES.

        Each Stockholder hereby severally agrees to tender in the Offer to Sub,
and Sub hereby agrees to purchase, subject to the terms and conditions set forth
herein, all Subject Shares set forth opposite such Stockholder's name on
Schedule A hereto at a price per Share equal to the Offer Price (as the same may
be increased by Sub). Sub may direct that such Stockholder tender





                                       2








<PAGE>

such Subject Shares and, subject to applicable Federal securities law, not
withdraw any Subject Shares so tendered.

3.      CONDITIONS.

        Parent's and Sub's obligations to purchase and each Stockholders'
obligations to sell the Subject Shares pursuant to Section 2 of this Agreement
shall be subject to the prior satisfaction or waiver of the following
conditions:

        (a) Sub shall have accepted the Shares for payment under the terms of
the Offer;

        (b) the Minimum Condition shall have been satisfied;

        (c) all regulatory approvals required by any applicable law, rule, or
regulation, including any applicable local, state, federal or foreign
regulation, shall have been obtained, and each such approval shall be final; and

        (d) there exist no preliminary or permanent injunction, or any other
order by any court of competent jurisdiction, restricting, preventing or
prohibiting either the purchase, or the delivery, of the Subject Shares.

4.      REPRESENTATION AND WARRANTY OF PARENT AND SUB.

        (a) Authority. Parent and Sub have all requisite power and authority to
enter into this Agreement and to consummate the transactions contemplated
hereby. The execution, delivery and performance of this Agreement by Parent and
Sub, and the consummation of the transactions contemplated hereby, have been
duly authorized by all necessary action on the part of the Parent and Sub. This
Agreement has been duly executed and delivered by the Parent and Sub and
constitutes a valid and binding obligation of the Parent and Sub enforceable
against the Parent and Sub in accordance with its terms. Except for
informational filings with the SEC, the execution and delivery of this Agreement
do not, and the consummation of the transactions contemplated hereby and
compliance with the terms hereof will not, (i) conflict with, or result in any
violation of, or default (with or without notice or lapse of time or both) under
any provision of, any certificate or articles of incorporation, bylaws,
certificate or articles of limited partnership, limited partnership agreement,
trust agreement, loan or credit agreement, note, bond, mortgage, indenture,
lease or other agreement, instrument, permit, concession, franchise, license,
judgment, order, notice, decree, statute, law, ordinance, rule or regulation
applicable to the Parent or Sub or to the Parent's or Sub's property or assets,
(ii) require any filing with, or permit, authorization, consent or approval of,
or notice to, any federal, state or local government or any court, tribunal,
administrative agency or commission or other governmental or regulatory
authority or agency, domestic, foreign or supranational, or (iii) violate any
order, writ, injunction, decree, statute, rule or regulation applicable to the
Parent or Sub or any of the Parent's or Sub's properties or assets.



                                       3








<PAGE>

        (b) Brokers. No broker, finder, investment banker or other person is
entitled to any brokerage, finder's or other fee or commission for which any
Stockholder will be liable in connection with the execution of this Agreement by
Parent and Sub or the performance by Parent and Sub of their obligations
hereunder.

        (c) Financing. Parent has sufficient funds available, directly or
through finance commitments, to purchase, or to cause Sub to purchase, all the
Subject Shares pursuant to this Agreement and to pay all fees and expenses
payable by Parent or Sub related to the transactions contemplated by this
Agreement.

5.      COVENANTS OF EACH STOCKHOLDER.

        Until the termination of this Agreement in accordance with Section 10,
each Stockholder, severally and not jointly, agrees as follows:

        (a) In connection with the closing of the purchase and sale contemplated
under Section 2 of this Agreement (other than pursuant to the Offer), each
Stockholder agrees to deliver, either to Sub or as directed by Parent, all
certificates evidencing the Subject Shares held by such Stockholder, duly
endorsed in blank for transfer, or accompanied by stock powers and such other
documents as may be necessary in Parent's judgment to transfer record ownership
of the Subject Shares to Sub or as directed by Parent.

        (b) At any meeting of stockholders of the Company called to vote upon
the Merger and the Merger Agreement or at any adjournment thereof or in any
other circumstances upon which a vote, consent or other approval (including by
written consent) with respect to the Merger and the Merger Agreement is sought,
the Stockholder shall vote (or cause to be voted) the Subject Shares in favor of
the Merger, the adoption by the Company of the Merger Agreement and the approval
of the terms thereof and each of the other transactions contemplated by the
Merger Agreement.

        (c) At any meeting of stockholders of the Company or at any adjournment
thereof or in any other circumstances upon which the Stockholder's vote, consent
or other approval is sought, the Stockholder shall vote (or cause to be voted)
the Subject Shares (and each class thereof) against (i) any Alternative
Transaction as such term is defined in Section 6.2 of the Merger Agreement, (ii)
any amendment of the Company's articles of organization or by-laws or other
proposal or transaction involving the Company, which amendment or other proposal
or transaction would be reasonably likely to impede, frustrate, prevent or
nullify the Merger, the Merger Agreement or any of the other transactions
contemplated by the Merger Agreement or change in any manner the voting rights
of any class of Company Common Stock, or (iii) any action that would cause the
Company to breach any representation, warranty or covenant contained in the
Merger Agreement. Subject to Section 12, the Stockholder further agrees not to
enter into any agreement or take any action inconsistent with the foregoing.

        (d) The Stockholder shall not, prior to the earliest of (i) the
Effective Time and (ii) the termination of the Merger Agreement in accordance
with its terms, (A) sell, transfer, give, pledge, assign or otherwise dispose of
(including by gift) (collectively, "Transfer"), or consent to






                                       4








<PAGE>

any Transfer of, any or all of such Subject Shares or any interest therein or
enter into any contract, option or other arrangement (including any profit
sharing arrangement) with respect to the Transfer of, the Subject Shares to any
person other than pursuant to the terms of the Offer or the Merger or (B) enter
into any voting arrangement, directly or indirectly, whether by proxy, voting
agreement or otherwise, in respect of the Subject Shares, and the Stockholder
agrees not to commit or agree to take any of the foregoing actions.

        (e) Such Stockholder, and any beneficiary of a revocable trust for which
such Stockholder serves as trustee, shall not take any action to revoke or
terminate such trust or take any other action which would restrict, limit or
frustrate in any way the transactions contemplated by this Agreement. Each such
beneficiary hereby acknowledges and agrees to be bound by the terms of this
Agreement applicable to it.

6.      GRANT OF IRREVOCABLE PROXY; APPOINTMENT OF PROXY.

        (a) Each Stockholder hereby irrevocably grants to, and appoints, Sub and
Robb Anderson, President of Sub, in his capacity as an officer of Sub, and any
individual who shall hereafter succeed to any such office of Sub, such
Stockholder's proxy and attorney-in-fact (with full power of substitution), for
and in the name, place and stead of such Stockholder, to vote such Stockholder's
Subject Shares, or grant a consent or approval in respect of such Subject Shares
against (i) any Alternative Transaction as such term is defined in Section 6.2
of the Merger Agreement, (ii) any amendment of the Company's articles of
organization or by-laws or other proposal or transaction involving the Company,
which amendment or other proposal or transaction would be reasonably likely to
impede, frustrate, prevent or nullify the Merger, the Merger Agreement or any of
the other transactions contemplated by the Merger Agreement or change in any
manner the voting rights of any class of Company Common Stock, or (iii) any
action that would cause the Company to breach any representation, warranty or
covenant contained in the Merger Agreement. The proxy granted pursuant to this
Section shall terminate upon the termination of this Agreement pursuant to
Section 10.

        (b) Such Stockholder represents that there are no proxies heretofore
given in respect of such Stockholder's Subject Shares.

        (c) Such Stockholder hereby affirms that the irrevocable proxy set forth
in this Section 6 is given in connection with the execution of the Merger
Agreement, and that such irrevocable proxy is given to secure the performance of
the duties of the Stockholder under this Agreement. Such Stockholder hereby
further affirms that the irrevocable proxy is coupled with an interest and may
under no circumstances be revoked. Such Stockholder hereby ratifies and confirms
all that the holder of such irrevocable proxy may lawfully do or cause to be
done by virtue hereof. Such irrevocable proxy is executed and intended to be
irrevocable in accordance with the provisions of Section 41 of the Massachusetts
Business Corporation Law (the "MBCL").




                                       5









<PAGE>

7.      FURTHER ASSURANCES.

        Each Stockholder will, at Parent's expense, from time to time, execute
and deliver, or cause to be executed and delivered, such additional or further
consents, documents and other instruments as Parent may reasonably request for
the purpose of effectively carrying out the transactions contemplated by this
Agreement.

8.      CERTAIN EVENTS.

        (a) Each Stockholder agrees that this Agreement and the obligations
hereunder shall attach to such Stockholder's Subject Shares and shall be binding
upon any person or entity to which legal or beneficial ownership of such Subject
Shares shall pass, whether by operation of law or otherwise, including without
limitation such Stockholder's heirs, guardians, administrators or successors. In
the event of any stock split, stock dividend, merger, reorganization,
recapitalization or other change in the capital structure of the Company
affecting the Company Common Stock, or the acquisition of additional shares of
Company Common Stock or other voting securities of the Company by any
Stockholder, the number of Subject Shares listed in Schedule A beside the name
of such Stockholder shall be adjusted appropriately and this Agreement and the
obligations hereunder shall attach to any additional shares of Company Common
Stock or other voting securities of the Company issued to or acquired by such
Stockholder.

        (b) Each Stockholder agrees that such Stockholder will tender to the
Company, immediately after the execution hereof (or, in the event Subject Shares
are acquired subsequent to the date hereof, immediately after such acquisition),
any and all certificates representing such Stockholder's Subject Shares in order
that the Company may inscribe upon such certificates the legend in accordance
with Section 7.9 of the Merger Agreement.

9.      ASSIGNMENT.

        Neither this Agreement nor any of the rights, interests or obligations
hereunder shall be assigned by any of the parties without the prior written
consent of the other parties, except that (i) Sub may assign, in its sole
discretion, any or all of its rights, interests and obligations hereunder to any
subsidiary of Parent that may be substituted for Sub as contemplated by Section
10.8 of the Merger Agreement, and (ii) Parent may assign, in its sole
discretion, any and all of its rights, interests and obligations hereunder to
any direct or indirect wholly owned subsidiary of Parent, provided that Parent
will continue to remain primarily liable for its obligations hereunder in the
event of any assignment pursuant to this clause (ii). Subject to the preceding
sentence, this Agreement will be binding upon, inure to the benefit of and be
enforceable by the parties and their respective successors and permitted
assigns.

10.     TERMINATION.

        This Agreement, and all rights and obligations of the parties hereunder,
shall terminate upon the date upon which the Merger Agreement is terminated in
accordance with its terms.




                                       6








<PAGE>

11.     GENERAL PROVISIONS.

        (a) Amendments. This Agreement may not be amended except by an
instrument in writing signed by each of the parties hereto.

        (b) Notice. All notices and other communications hereunder shall be in
writing and shall be deemed given when delivered by facsimile (with confirmation
of delivery) or personally or sent by overnight courier (providing proof of
delivery) to Parent in accordance with Section 10.2 of the Merger Agreement and
to the Stockholders at their respective addresses and facsimile numbers set
forth on Schedule A attached hereto (or at such other address and facsimile
number for a party as shall be specified by like notice).

        (c) Interpretation. When a reference is made in this Agreement to an
Article or a Section, such reference shall be deemed made to an Article or a
Section of this Agreement, unless otherwise indicated. The headings contained in
this Agreement are for reference purposes only and shall not affect in any way
the meaning or interpretation of this Agreement. Unless the context otherwise
requires, words importing the singular shall include the plural, and vice versa.
Wherever the words "include," "includes" or "including" are used in this
Agreement, they shall be deemed to be followed by the words "without
limitation." Capitalized terms used and not otherwise defined in this Agreement
shall have the respective meanings assigned to them in the Merger Agreement.

        (d) Counterparts. This Agreement may be executed in one or more
counterparts, all of which shall be considered one and the same agreement, and
shall become effective when one or more of the counterparts have been signed by
each of the parties and delivered to the other party, it being understood that
each party need not sign the same counterpart.

        (e) Entire Agreement; No Third-Party Beneficiaries. This Agreement
(including the documents and instruments referred to herein) (i) constitutes the
entire agreement and supersedes all prior agreements and understandings, both
written and oral, among the parties with respect to the subject matter hereof
and (ii) is not intended to confer upon any person other than the parties hereto
any rights or remedies hereunder.

        (f) Governing Law. This Agreement shall be governed by, and construed in
accordance with, the laws of the Commonwealth of Massachusetts regardless of the
laws that might otherwise govern under applicable principles of conflicts of law
thereof.

        (g) Expenses. Except as otherwise provided herein, all costs and
expenses incurred in connection with the transactions contemplated by this
Agreement shall be paid by the party incurring such expenses.







                                       7








<PAGE>

12.     STOCKHOLDER CAPACITY.

        No person executing this Agreement who is or becomes during the term
hereof a director or officer of the Company makes any agreement or understanding
herein in his capacity as such director or officer. Each Stockholder signs
solely in his capacity as the record holder and beneficial owner of, or the
trustee of a trust whose beneficiaries are the beneficial owners of, such
Stockholder's Subject Shares and nothing herein (including, without limitation,
the provisions of Section 5(e)) shall limit or affect any actions taken by a
Stockholder in his capacity as an officer or director of the Company.

13.     ENFORCEMENT.

        The parties agree that irreparable damage would occur in the event that
any of the provisions of this Agreement were not performed in accordance with
their specific terms or were otherwise breached. It is accordingly agreed that
the parties shall be entitled to an injunction or injunctions to prevent
breaches of this Agreement and to enforce specifically the terms and provisions
of this Agreement in any court of the United States located in the Commonwealth
of Massachusetts or in a Massachusetts state court, this being in addition to
any other remedy to which they are entitled at law or in equity. In addition,
each of the parties hereto (i) consents to submit such party to the personal
jurisdiction of any Federal court located in the Commonwealth of Massachusetts
or any Massachusetts state court in the event any dispute arises out of this
Agreement or any of the transactions contemplated hereby, (ii) agrees that such
party will not attempt to deny or defeat such personal jurisdiction by motion or
other request for leave from any such court, (iii) agrees that such party will
not bring any action relating to this Agreement or the transactions contemplated
hereby in any court other than a Federal court sitting in the Commonwealth of
Massachusetts or a Massachusetts state court and (iv) waives any right to trial
by jury with respect to any claim or proceeding related to or arising out of
this Agreement or any of the transactions contemplated hereby.

14.     PUBLIC ANNOUNCEMENTS.

        No Stockholder shall issue any press release or make any public
statement without the prior written consent of Parent, except as may be required
by applicable law, court process or by obligations pursuant to any listing
agreement with any national securities exchange.




                                       8










<PAGE>



        IN WITNESS WHEREOF, Parent, Sub and the Stockholders have caused this
Agreement to be duly executed and delivered as of the date first written above.

PERBIO SCIENCE AB

By: /s/ Magnus Lindqvist
_______________________________________
Name:   Magnus Lindqvist
Title:  Director, PerBio Science AB
        Chief Financial Officer, Perstorp AB



By: /s/ Mats Fischier
_______________________________________
Name:   Mats Fischier
Title:  Director, PerBio Science AB
        Chief Executive Officer, Perstorp Life Science


EWOK ACQUISITION CORP.



By: /s/ Robb Anderson
_______________________________________
Name:   Robb Anderson
Title:  President


STOCKHOLDERS:


     /s/ Charles R. Burke
_______________________________________
Name:  Charles R. Burke


     /s/ Christine A. Burns
_______________________________________
Name:  Christine A. Burns


     /s/ Avery W. Catlin
_______________________________________
Name:  Avery W. Catlin


    /s/ Owen A. Dempsey
_______________________________________
Name:  Owen A. Dempsey






                                        9








<PAGE>



     /s/ Wallace G. Dempsey
_______________________________________
 Name:  Wallace G. Dempsey



    /s/ Irwin J. Gruverman
_______________________________________
Name:  Irwin J. Gruverman



    /s/ Hayden H. Harris
_______________________________________
Name:  Hayden H. Harris



    /s/ Wolfgang Woloszczuk
_______________________________________
Name:   Wolfgang Woloszczuk


G & G DIAGNOSTICS LIMITED PARTNERSHIP I



By: /s/ Irwin J. Gruverman
_______________________________________
Name:   Irwin J. Gruverman
Title:  General Partner



[HARRIS TRUST]


By: /s/ Hayden H. Harris
_______________________________________
Name:   Hayden H. Harris Living Trust Dated 3/6/98
Title:  Trustee



     /s/ Hayden H. Harris
_______________________________________
Name:   Hayden H. Harris






                                       10









<PAGE>


                                   SCHEDULE A

<TABLE>
<CAPTION>
Name and Address of Stockholder                    Number of Shares of Company Common
                                                   Stock Owned

<S>                                                         <C>
Charles R. Burke                                            -1,000-
c/o Monument Partners, Inc.
1410-1 Monument Street
Concord, MA 01742

Christine A. Burns                                              -0-
9 Salem Road
Wellesley, MA 02181

Avery W. Catlin                                             -1,000-
241 Central Street
Hingham, MA 02043

Owen A. Dempsey                                           -255,100-
21 Harris Street
Brookline, MA 02146

Wallace G. Dempsey                                        -160,000-
487 Scarsdale Road
Tuckahoe, NY 10707

Irwin J. Gruverman                                         -12,000-
16 Tanglewood Road
Needham, MA 02494

G&G Diagnostics Limited                                    -95,000-
Partnership I
30 Ossipee Road
Newton, MA 02164

Hayden H. Harris                                            -3,500-
c/o Enterprise Management
425 Main Street
Ann Arbor, MI 48104

[HARRIS TRUST]                                              -2,000-
c/o Enterprise Management
425 Main Street
Ann Arbor, MI 48104

Wolfgang Woloszczuk                                        -40,000-
c/o Biomedica GmbH
Divischgasse 4
A-1210 Vienna
AUSTRIA

</TABLE>











<PAGE>



                              EMPLOYMENT AGREEMENT

         THIS AGREEMENT is entered into this 27th day of May, 1999,
by and between EWOK ACQUISITION CORP., a Massachusetts corporation (hereinafter
"EWOK"), and OWEN A. DEMPSEY (hereinafter "DEMPSEY").

         WHEREAS, EWOK is proposing to acquire DEMPSEY's present employer,
ENDOGEN, Inc. (hereinafter "CORPORATION") in which event the operations of EWOK
and CORPORATION will merge; and

         WHEREAS, assuming said merger is consummated and the contingencies set
forth in Section 8.2 below are satisfied, EWOK wishes to employ DEMPSEY as its
President under the terms and conditions set forth in this Agreement; and

         WHEREAS, in such event DEMPSEY wishes to be employed by EWOK as its
         President under those same terms and conditions.

         NOW, THEREFORE, in consideration of the above and the promises and
agreements set forth in this Agreement, the parties agree as follows:

         1.       EMPLOYMENT.

                  EWOK agrees to employ DEMPSEY and DEMPSEY accepts employment
         with EWOK as its President.

         2.       DUTIES AND RESPONSIBILITIES.

                  As President, DEMPSEY will devote his entire time, attention
         and energy to such duties, shall perform the duties and assignments
         usually associated with that position and such other duties and
         assignments, consistent with his position as President of EWOK, as may
         be assigned to him from to time-to-time by the Chairman of the Board of
         Directors of EWOK or his designee. The above notwithstanding, EWOK
         reserves the right following






<PAGE>


         the merger to change  DEMPSEY's job title after the employment date (as
         defined in Section 8.2 below)  provided  that such does not result in a
         substantial  diminution  of  DEMPSEY's  job  responsibilities  as  they
         existed on the effective date of this Agreement.

                DEMPSEY will not during the term of this Agreement be engaged in
         any other business or employment (including self-employment) without
         the express written consent of the chairman of the Board of Directors
         of EWOK or his designee. However, with the advance approval of EWOK
         (through the Chairman of its Board of Directors or his designee),
         DEMPSEY may serve on the Boards of Directors of charitable
         organizations and/or outside corporations provided such activities do
         not constitute an actual or potential conflict of interest with and/or
         unduly interfere with the performance of DEMPSEY's duties and
         responsibilities hereunder.

         3.     COMPENSATION.

                3.1   Base Salary.

                      For all services rendered by DEMPSEY under this Agreement,
                EWOK will pay an initial base salary of $160,000.00 per calendar
                year (which shall be pro-rated for partial calendar years
                hereunder), payable in equal installments on a schedule
                consistent with EWOK's payroll practices for executive
                employees. EWOK shall deduct from that base salary (as well as
                any adjustments to base salary pursuant to Section 3.2 below)
                all state and federal taxes and other assessments required by
                law.

                3.2   Adjustments to Base Salary.

                      The Chairman of the Board of Directors of EWOK or his
                designee shall review DEMPSEY's salary and performance on an
                annual basis (commencing on or

                                       2






<PAGE>



                about January 1, 2000, and on or about January 1 of each
                succeeding year while DEMPSEY remains employed by EWOK) and may,
                in his discretion, make increases to the base salary based upon
                DEMPSEY's performance in the preceding year. Adjustments to the
                base salary, if any, shall be effective as of January 1 of the
                involved year.

                3.3   Bonuses.

                      DEMPSEY shall be entitled to earn up to an additional
                $60,000.00 per calendar year in keeping with the provisions of a
                bonus plan which shall, hereafter, be mutually agreed upon by
                DEMPSEY and EWOK. The terms of that bonus plan (including
                eligibility factors therefor) shall be agreed upon by EWOK
                (through the Chairman of its Board of Directors or his designee)
                and DEMPSEY within ninety (90) days of the effective date of
                this Agreement.


                3.4   Vehicle Allowance.

                      DEMPSEY shall receive a vehicle allowance equivalent to
                the sum of $10,000.00 per calendar year (which shall be
                pro-rated for partial calendar years hereunder) which shall be
                payable as income to DEMPSEY and, therefore, subject to the
                deduction of all state and federal taxes and other assessments
                required by law.

         4.     BENEFITS AND PERQUISITES.


                  Subject to applicable federal and state tax regulations,
         DEMPSEY shall receive the following benefits and perquisites from EWOK:

                4.1   Insurance.

                                      3






<PAGE>


                      DEMPSEY shall be eligible for medical insurance (including
                coverage for eligible dependents), disability insurance and life
                insurance coverages under the same terms and conditions as those
                benefits are made available to similarly-situated executive
                employees of EWOK.

                4.2   Vacation.

                      DEMPSEY shall be entitled to paid vacation under the same
                terms and conditions as those benefits are made available to
                similarly-situated executive employees of EWOK. The use and
                scheduling of that vacation by DEMPSEY shall be consistent with
                requirements of his position and shall not interfere with the
                performance of his responsibilities as President of EWOK.

                4.3   Expense Account.

                      EWOK agrees to pay on DEMPSEY's behalf all reasonable and
                customary business-related expenses incurred by him in the
                provision of services under this Agreement. Included within this
                obligation are all customer entertainment, business travel and
                other expenses reasonably attributable to the provision of
                services under this Agreement. Payment of expense account items
                are subject to the approval of the Chairman of the Board of
                Directors (or his designee) of EWOK and should be submitted by
                DEMPSEY for approval on a monthly basis.


         5.     NON-DISCLOSURE/NON-COMPETITION.

                5.1   Non-Disclosure.

                      DEMPSEY recognizes and acknowledges that information
                obtained by him during the course of his employment with EWOK,
                its trade secrets, business and

                                       4






<PAGE>



                customers, is confidential information. The parties to this
                Agreement further stipulate that the information referred to in
                Section 5 of this Agreement is sufficiently secret that EWOK
                derives economic value from the information remaining
                confidential and not being generally known to other persons who
                can obtain economic value from its disclosure or use. DEMPSEY
                also acknowledges that EWOK has taken precautions, such as this
                Agreement, to keep such information confidential. DEMPSEY will
                not, both during and after the termination of this Agreement
                (for whatever reason), disclose or communicate to any person,
                firm, corporation or other entity, in any manner, any trade
                secrets, proprietary or confidential information of EWOK,
                CORPORATION and/or PerBio Science AB. Such information includes,
                but is not limited to, the following:

                      Technical or Non-Technical Data, Formula, Patterns,
                      Compilations, Devices, Methods, Techniques, Drawings,
                      Processes, Customer Lists, Business and/or Marketing
                      Development Plans or Information or other data of a
                      similar nature or description.

                      The above provisions shall be inapplicable to the
                disclosure of information which (1) was part of the public
                domain prior to the effective date of this Agreement, (2) is
                required as part of a legal proceeding (but only to the extent
                that the disclosure of the information is legally compelled)
                and/or (3) information that becomes part of the public domain as
                the result of the disclosure of such information by third
                parties through no fault, direct or indirect, of DEMPSEY.


                5.2   Non-Competition.

                      DEMPSEY acknowledges the substantial time and effort
                expended by EWOK and CORPORATION in establishing the
                long-standing relationships they have with their customers.
                DEMPSEY agrees that during his employment with EWOK and for a
                period

                                       5






<PAGE>


                of one (1) year following termination of his employment with
                EWOK (for whatever reason), he will not, directly or indirectly,
                either for himself or for any other person, firm, partnership,
                agency, corporation or other entity, compete in their lines of
                business with EWOK, CORPORATION, PerBio Science AB and/or its or
                their respective subsidiaries or affiliates for which DEMPSEY
                had material responsibility during the course of his employment
                with EWOK or CORPORATION or solicit, call upon, divert or take
                away or attempt to solicit, divert or take away from EWOK,
                CORPORATION, PerBio Science AB and/or its or their respective
                subsidiaries or affiliates for which DEMPSEY had material
                responsibility during the course of his employment with EWOK or
                CORPORATION any of their actual or potential customers nor
                assist any other person or entity in doing so within the United
                States of America. DEMPSEY represents that his experience and
                capabilities are such that he can obtain employment in a
                non-competitive area and that, in the event of the termination
                of this Agreement, enforcement of this covenant by way of
                injunction will not impair or prevent DEMPSEY from earning a
                livelihood.

                5.3   Rights and Remedies.

                      The parties further stipulate that the matters covered in
                this Agreement are important, material, confidential and gravely
                affect the successful conduct, business and good-will of EWOK
                and/or PerBio Science AB. The parties agree that EWOK and/or
                PerBio Science AB may enforce this Agreement by seeking
                equitable and injunctive relief, as well as monetary damages,
                attorneys' fees and costs of suit. The obligations set forth in
                this Section 5 shall survive the "term" or the termination of
                this Agreement pursuant to the provisions of Sections 6 or 7
                below, for whatever reason.

                5.4   Separability.

                                       6






<PAGE>


                      EWOK and DEMPSEY agree that the character, duration and
                geographic scope of the provisions set forth in this Section 5
                are reasonable in light of the circumstances as they exist on
                the date hereof. Should a decision, however, be made at a later
                date by a court of competent jurisdiction that the character,
                duration or geographic scope of said provisions is unreasonable,
                it is the intention and the agreement of DEMPSEY and EWOK that
                the provisions of this Section 5 shall be construed by the court
                in such a manner as to impose only those restrictions on
                DEMPSEY's conduct that are reasonable in light of the
                circumstances and as are necessary to assure to EWOK and/or
                PerBio Science AB the benefits provided under Section 5. If, in
                a judicial proceeding, a court shall refuse to enforce all of
                the separate promises included therein because taken together
                they are more extensive than necessary to assure EWOK and/or
                PerBio Science AB the intended benefits of Section 5, it is
                expressly understood and agreed by the parties hereto that the
                provisions of Section 5 that, if eliminated, would permit the
                remaining separate provisions to be enforced in such proceeding
                shall be deemed eliminated for purposes of such proceeding from
                Section 5.


        6.      TERM.

                The initial term of this Agreement is for a period of two (2)
         years, commencing on the "employment date" (as defined in Section 8.2
         below) and terminating two (2) years hence, unless sooner terminated
         pursuant to the provisions of this Agreement. In the event that EWOK
         does not intend to renew this agreement upon the completion of its
         initial term, EWOK shall provide DEMPSEY with a minimum of ninety (90)
         days advance written notice prior to the expiration date of this
         Agreement's initial term; in the event of such advance written notice,
         EWOK may, in its discretion, place DEMPSEY on a leave of absence for
         all or any portion of that ninety (90) day period. Provided, however,
         that the failure to provide the notice required hereunder shall not


                                       7






<PAGE>



         result in the extension of the term of this Agreement unless the
         parties have mutually agreed, in writing, to such an extension.

         7.     TERMINATION.

                7.1   Term.

                      The Agreement shall expire upon the expiration of its term
                unless otherwise sooner terminated by the parties' written
                mutual agreement or pursuant to the remaining provisions of this
                Section 7.

                7.2   Termination for Cause.

                      EWOK may terminate this Agreement prior to the expiration
                of its term for cause without further obligation to DEMPSEY
                hereunder. For purposes of this Agreement, "for cause" includes
                the following:


                (a)   an intentional act of fraud, embezzlement, theft or any
                      other material violation of the law including those
                      involving dishonesty in connection with DEMPSEY's duties
                      or in the course of his employment with EWOK or the
                      commission of a felony; or

                (b)   intentional wrongful damage to material assets of EWOK; or

                (c)   intentional wrongful disclosure of material confidential
                      information of EWOK.; or

                (d)   intentional conduct by DEMPSEY which has resulted or may
                      result in financial loss and legal liability to EWOK which
                      is materially injurious to EWOK.

                No act, or failure to act, on the part of DEMPSEY, shall be
                deemed "intentional" if it was due primarily to an error in
                judgment or negligence, but shall be deemed "intentional" only
                if done, or omitted to be done, by DEMPSEY not in good faith and
                without reasonable belief that his action or omission was in the
                best interests of EWOK. In the

                                       8






<PAGE>



                event of a termination "for cause" under the provisions of this
                Section 7.2, DEMPSEY shall not be entitled to the salary
                continuation provided in Section 7.6 below.

                7.3 Termination Without Cause.

                      DEMPSEY may terminate this Agreement upon the provision of
                six (6) months written notice to EWOK. Similarly, EWOK may, in
                its discretion, terminate this Agreement without cause upon the
                provision of six (6) months written notice to DEMPSEY provided
                that EWOK thereafter complies with the applicable provisions of
                Section 7.6 below.

                      In the event of written notice of termination by DEMPSEY
                or EWOK under this Section, EWOK may, in its discretion, place
                DEMPSEY on a leave of absence for all or any portion of that six
                (6) month notice period up to and including the effective date
                of DEMPSEY's termination from employment.

                7.4   Termination Upon Death or Disability.

                      EWOK may terminate this Agreement without further
                obligation to DEMPSEY hereunder upon the death or permanent
                disability of DEMPSEY. For purposes of this Agreement, the
                "permanent disability" of DEMPSEY shall be deemed to occur if
                the Board of Directors of EWOK determines, based upon competent
                medical evidence, that DEMPSEY is unable to substantially
                perform the services required of him, hereunder, with or without
                a reasonable accommodation, for a continuous period of ninety
                (90) days or more. DEMPSEY shall cooperate with EWOK in
                providing medical information necessary for EWOK to assess the
                parties' respective duties and obligations under the provisions
                of this Section.

                7.5   Termination by DEMPSEY for "Good Reason"

                                       9






<PAGE>


                      DEMPSEY's employment under this Agreement may be
                terminated for good reason (as set forth below) by written
                notice from him to the Chairman of the Board of Directors of
                EWOK at least thirty (30) days prior to a date of termination
                subsequent to the occurrence of any of the following events:

                (a)   a reasonable determination by DEMPSEY in good faith that
                      there has been a significant adverse change in the nature
                      or scope of DEMPSEY's responsibilities, authorities,
                      powers, functions or duties; or

                (b)   a reduction in DEMPSEY's monetary compensation; or

                (c)   the relocation of DEMPSEY's offices at which DEMPSEY is
                      principally employed to a location more than 50 miles from
                      the location where DEMPSEY is principally employed; or

                (d)   the failure by EWOK to pay to DEMPSEY any portion of his
                      current compensation or the failure by EWOK to continue in
                      effect any material compensation, incentive, bonus or
                      benefit plan in which DEMPSEY participates pursuant to the
                      provisions of this Agreement unless an equitable
                      arrangement (embodied in an ongoing substitute or
                      alternative plan) has been made with respect to such plan,
                      or the failure by EWOK to continue DEMPSEY's participation
                      therein (or in such substitute or alternative plan) on a
                      basis not materially less favorable, both in terms of the
                      amount of benefits provided and the level of DEMPSEY's
                      participation, relative to the other participants.

                The above provisions notwithstanding, "good reason" shall not be
                deemed to exist if any or all of the events noted in this
                Section 7.5 have been agreed upon in advance by DEMPSEY and
                EWOK.


                                       10






<PAGE>


                7.6   Salary Continuation.

                      Subject to the provisions of this Section 7.6, DEMPSEY
                will be provided with salary continuation upon termination of
                this Agreement prior to its term as specified below. If a
                termination during the term of this Agreement occurs pursuant to
                the provisions of Section 7.3 above due to notice of termination
                provided by EWOK, or in the event that this Agreement is not
                renewed and DEMPSEY's employment is terminated at the expiration
                of its initial term (as provided in Section 6 above), DEMPSEY's
                salary (as provided in Section 3.1 above) shall be continued for
                a period of twelve (12) months from the effective date of
                termination; provided, however, that in no event shall DEMPSEY
                receive salary continuation if he has provided notice of
                termination to EWOK pursuant to the provisions of Section 7.3 or
                if the Agreement has been terminated "for cause" as specified in
                Section 7.2 above. Further, in the event of DEMPSEY's
                termination of this Agreement for "good reason" (as specified in
                Section 7.5 above), DEMPSEY's salary (as provided in Section 3.1
                above) shall be continued for a period of six (6) months from
                the effective date of termination.

                      The above notwithstanding, DEMPSEY shall not be entitled
                to the salary continuation provided in this Section 7.6 unless
                and until he has signed and delivered to EWOK a binding
                agreement in a form acceptable to EWOK setting forth a release
                of any and all claims arising from his employment, termination
                from employment and termination of this Agreement with EWOK.
                During the period of salary continuation (regardless of
                duration), DEMPSEY shall not be entitled to continuation of the
                other benefits or perquisites provided in this Agreement unless
                otherwise required by law or by the mutual agreement of the
                parties hereto. Further, in no event shall DEMPSEY be entitled
                to receive multiple payments of salary continuation under the
                provisions of this

                                       11







<PAGE>


                Section 7.6 should his termination from employment with EWOK be
                claimed or determined to be attributable, in whole or in part,
                to two or more of the reasons specified in this Section.


                7.7   Property of the Business.

                      Upon DEMPSEY's termination of employment (for any reason),
                all memoranda, notes, lists, records and other documents or
                papers (and all copies thereof) including items stored in
                computer memories, on microfiche or by any other means, made or
                compiled by or on behalf of DEMPSEY, or made available to
                DEMPSEY relating to the business of EWOK, are and shall be
                EWOK's property and shall, if in the possession of DEMPSEY, be
                promptly delivered to EWOK.


         8.     MODIFICATION; CONTINGENCIES AND ASSIGNMENT.

                8.1   Modification.

                      This Agreement may not be modified except in writing
                signed by both parties.

                8.2   Contingencies and Assignment.

                      The obligations of DEMPSEY and EWOK under this Agreement
                are contingent upon EWOK's consummation of its merger with
                CORPORATION as set forth below. For purposes of this Agreement,
                the consummation of that merger and DEMPSEY's "employment date"
                shall be deemed to have occurred on the date, if any, on which
                EWOK accepts for payment shares tendered pursuant to EWOK's
                tender offer for all of the issued and outstanding common stock
                of CORPORATION. In the event that said contingency is not fully
                satisfied and the tender offer is not consummated, all
                obligations pursuant to this Agreement and the provisions of
                this Agreement shall be null, void and no longer in force or
                effect.

                                       12





<PAGE>



                      It is expressly agreed that the duties, rights and
                obligations of EWOK and DEMPSEY under this Agreement shall be
                transferred to any entity with which EWOK may merge on or
                following the "employment date" as set forth above.
                Additionally, EWOK or that entity may further assign such
                duties, rights and obligations to other entities following said
                merger provided said assignment is to a subsidiary of PerBio
                Science AB. EWOK or that entity shall provide DEMPSEY with
                written notice of said assignments; in that event, the
                obligations of DEMPSEY and EWOK as set forth in this Agreement
                shall, thereafter, be applicable to the entity identified in
                that notice. Except as specifically provided in this Section
                8.2, the duties, rights and obligations set forth in this
                Agreement shall not otherwise be assignable by EWOK or DEMPSEY
                to any other corporation or other entity without the other
                party's approval, in writing.


         9.     GOVERNING LAW.

                The performance and interpretation of this Agreement shall be
         construed in accordance with the laws of the State of Massachusetts.

         10.    WAIVER.


                Waiver of any breach of the terms and conditions of this
         Agreement shall not be construed to be a waiver of any preceding or
         succeeding breach of the same or different term or condition of this
         Agreement, and this Agreement shall continue and remain in full for and
         effect as if no waiver had occurred.

         11.    NOTICE.

                Notices shall be deemed delivered and received as of the date of
         the U.S. Postal Service postmark. Any notice required by this Agreement
         shall be sent by certified mail, return receipt requested, to the
         following addresses:

                                       13






<PAGE>



         To: EWOK

             c/o Chairman of the Board
             c/o Endogen, Inc.
             30 Commerce Way
             Woburn, MA  01801

             with a copy to:

             Mr. Robb Anderson
             Pierce Chemical Co.
             3747 Meridian Rd.
             Rockford, IL  61101

         To: OWEN A. DEMPSEY
             21 Harris Street
             Brookline, MA 02446

         12.    SEVERABILITY.

                In the event any of the terms and provisions of this Agreement
         are determined to be invalid or unlawful, the remaining provisions of
         this Agreement will continue in full force and effect to the fullest
         extent permitted by law. The parties expressly agree that a court of
         competent jurisdiction may modify the provisions of this Agreement so
         as to make the Agreement enforceable.

         13.    WARRANTY.

                DEMPSEY hereby warrants that neither the entry into this
         Employment Agreement nor its performance by DEMPSEY will conflict with
         or result in a breach of the terms, conditions or privileges of any
         agreement or other obligation of any nature to which DEMPSEY is a
         party, or

                                       14






<PAGE>



         by which DEMPSEY is bound, including without limitation, any employment
         agreements, non-competition agreements or confidentiality agreements
         previously entered into by DEMPSEY.

         EXECUTED on the 27th day of May, 1999.

EWOK ACQUISITION CORP., a Massachusetts
corporation


By:  /s/ Robb K. Anderson                 /s/  Owen A. Dempsey
- ------------------------------            -------------------------------------
Its: President                            OWEN A. DEMPSEY


ATTEST:

/s/
- ------------------------------


                                       15















<PAGE>


                              EMPLOYMENT AGREEMENT

        THIS AGREEMENT is entered into this 27th day of May, 1999,
by and between EWOK ACQUISITION CORP., a Massachusetts corporation (hereinafter
"EWOK"), and CHRISTINE A. BURNS (hereinafter "BURNS").

        WHEREAS, EWOK is proposing to acquire BURNS' present employer, ENDOGEN,
Inc. (hereinafter "CORPORATION") in which event the operations of EWOK and
CORPORATION will merge; and

        WHEREAS, assuming said merger is consummated and the contingencies set
forth in Section 8.2 below are satisfied, EWOK wishes to employ BURNS as its
Vice President of Product Development and Technology under the terms and
conditions set forth in this Agreement; and

        WHEREAS, in such event BURNS wishes to be employed by EWOK as its Vice
President of Development and Technology under those same terms and conditions.

        NOW, THEREFORE, in consideration of the above and the promises and
agreements set forth in this Agreement, the parties agree as follows:

        1      EMPLOYMENT.

               EWOK agrees to employ BURNS and BURNS accepts employment with
        EWOK as its Vice President of Development and Technology.

        2      DUTIES AND RESPONSIBILITIES.

               As Vice President of Development and Technology, BURNS will
        devote her entire time, attention and energy to such duties, shall
        perform the duties and assignments usually associated with that position
        and such other duties and assignments, consistent with her position as
        Vice President of Development and Technology of EWOK, as may be assigned
        to her from to time-to-time by the Chairman of the Board of Directors of
        EWOK or his







<PAGE>




        designee. The above notwithstanding, EWOK reserves the right
        following the merger to change BURNS' job title after the employment
        date (as defined in Section 8.2 below) provided that such does not
        result in a substantial diminution of BURNS' job responsibilities as
        they existed on the effective date of this Agreement.

               BURNS will not during the term of this Agreement be engaged in
        any other business or employment (including self-employment) without the
        express written consent of the chairman of the Board of Directors of
        EWOK or his designee. However, with the advance approval of EWOK
        (through the Chairman of its Board of Directors or his designee), BURNS
        may serve on the Boards of Directors of charitable organizations and/or
        outside corporations provided such activities do not constitute an
        actual or potential conflict of interest with and/or unduly interfere
        with the performance of BURNS' duties and responsibilities hereunder.

        3      COMPENSATION.

               3.1    Base Salary.

                      For all services rendered by BURNS under this Agreement,
               EWOK will pay an initial base salary of $144,000.00 per calendar
               year (which shall be pro-rated for partial calendar years
               hereunder), payable in equal installments on a schedule
               consistent with EWOK's payroll practices for executive employees.
               EWOK shall deduct from that base salary (as well as any
               adjustments to base salary pursuant to Section 3.2 below) all
               state and federal taxes and other assessments required by law.


                                       2







<PAGE>


               3.2    Adjustments to Base Salary.

                      The Chairman of the Board of Directors of EWOK or his
               designee shall review BURNS' salary and performance on an annual
               basis (commencing on or about January 1, 2000, and on or about
               January 1 of each succeeding year while BURNS remains employed by
               EWOK) and may, in his discretion, make increases to the base
               salary based upon BURNS' performance in the preceding year.
               Adjustments to the base salary, if any, shall be effective as of
               January 1 of the involved year. 3.3 Bonuses.

                      BURNS shall be entitled to earn up to an additional
               $36,000.00 per calendar year in keeping with the provisions of a
               bonus plan which shall, hereafter, be mutually agreed upon by
               BURNS and EWOK. The terms of that bonus plan (including
               eligibility factors therefor) shall be agreed upon by EWOK
               (through the Chairman of its Board of Directors or his designee)
               and BURNS within ninety (90) days of the effective date of this
               Agreement.

               3.4    Vehicle Allowance.

                      BURNS shall receive a vehicle allowance equivalent to the
               sum of $6,000.00 per calendar year (which shall be pro-rated for
               partial calendar years hereunder) which shall be payable as
               income to BURNS and, therefore, subject to the deduction of all
               state and federal taxes and other assessments required by law.


                                       3







<PAGE>



        4      BENEFITS AND PERQUISITES.

               Subject to applicable federal and state tax regulations, BURNS
        shall receive the following benefits and perquisites from EWOK:

               4.1 Insurance.

                      BURNS shall be eligible for medical insurance (including
               coverage for eligible dependents), disability insurance and life
               insurance coverages under the same terms and conditions as those
               benefits are made available to similarly-situated executive
               employees of EWOK. 4.2 Vacation.

                      BURNS shall be entitled to paid vacation under the same
               terms and conditions as those benefits are made available to
               similarly-situated executive employees of EWOK. The use and
               scheduling of that vacation by BURNS shall be consistent with
               requirements of her position and shall not interfere with the
               performance of her responsibilities as Vice President of
               Development and Technology of EWOK.

               4.3 Expense Account.

                      EWOK agrees to pay on BURNS' behalf all reasonable and
               customary business-related expenses incurred by her in the
               provision of services under this Agreement. Included within this
               obligation are all customer entertainment, business travel and
               other expenses reasonably attributable to the provision of
               services under this Agreement. Payment of expense account items
               are subject to the approval of the


                                       4







<PAGE>


               Chairman of the Board of Directors (or his designee) of EWOK and
               should be submitted by BURNS for approval on a monthly basis.

        5      NON-DISCLOSURE/NON-COMPETITION.

               5.1    Non-Disclosure.

                      BURNS recognizes and acknowledges that information
               obtained by her during the course of her employment with EWOK,
               its trade secrets, business and customers, is confidential
               information. The parties to this Agreement further stipulate that
               the information referred to in Section 5 of this Agreement is
               sufficiently secret that EWOK derives economic value from the
               information remaining confidential and not being generally known
               to other persons who can obtain economic value from its
               disclosure or use. BURNS also acknowledges that EWOK has taken
               precautions, such as this Agreement, to keep such information
               confidential. BURNS will not, both during and after the
               termination of this Agreement (for whatever reason), disclose or
               communicate to any person, firm, corporation or other entity, in
               any manner, any trade secrets, proprietary or confidential
               information of EWOK, CORPORATION and/or PerBio Science AB. Such
               information includes, but is not limited to, the following:

                      Technical or Non-Technical Data, Formula, Patterns,
                      Compilations, Devices, Methods, Techniques, Drawings,
                      Processes, Customer Lists, Business and/or Marketing
                      Development Plans or Information or other data of a
                      similar nature or description.

                      The above provisions shall be inapplicable to the
               disclosure of information which (1) was part of the public domain
               prior to the effective date of this Agreement, (2) is required as
               part of a legal proceeding (but only to the extent that the
               disclosure of the


                                       5







<PAGE>


               information is legally compelled) and/or (3) information that
               becomes part of the public domain as the result of the disclosure
               of such information by third parties through no fault, direct or
               indirect, of BURNS.

               5.2 Non-Competition.

                      BURNS acknowledges the substantial time and effort
               expended by EWOK and CORPORATION in establishing the
               long-standing relationships they have with their customers. BURNS
               agrees that during her employment with EWOK and for a period of
               one (1) year following termination of her employment with EWOK
               (for whatever reason), she will not, directly or indirectly,
               either for herself or for any other person, firm, partnership,
               agency, corporation or other entity, compete in their lines of
               business with EWOK, CORPORATION, PerBio Science AB and/or its or
               their respective subsidiaries or affiliates for which BURNS had
               material responsibility during the course of her employment with
               EWOK or CORPORATION or solicit, call upon, divert or take away or
               attempt to solicit, divert or take away from EWOK, CORPORATION,
               PerBio Science AB and/or its or their respective subsidiaries or
               affiliates for which BURNS had material responsibility during the
               course of her employment with EWOK or CORPORATION any of their
               actual or potential customers nor assist any other person or
               entity in doing so within the United States of America. BURNS
               represents that her experience and capabilities are such that she
               can obtain employment in a non-competitive area and that, in the
               event of the termination of this Agreement, enforcement of this
               covenant by way of injunction will not impair or prevent BURNS
               from earning a livelihood.

               5.3 Rights and Remedies.

                      The parties further stipulate that the matters covered in
               this Agreement are important, material, confidential and gravely
               affect the successful conduct, business and


                                       6







<PAGE>


              good-will of EWOK and/or PerBio Science AB. The parties agree that
              EWOK and/or PerBio Science AB may enforce this Agreement by
              seeking equitable and injunctive relief, as well as monetary
              damages, attorneys' fees and costs of suit. The obligations set
              forth in this Section 5 shall survive the "term" or the
              termination of this Agreement pursuant to the provisions of
              Sections 6 or 7 below, for whatever reason.

               5.4    Separability.

                      EWOK and BURNS agree that the character, duration and
               geographic scope of the provisions set forth in this Section 5
               are reasonable in light of the circumstances as they exist on the
               date hereof. Should a decision, however, be made at a later date
               by a court of competent jurisdiction that the character, duration
               or geographic scope of said provisions is unreasonable, it is the
               intention and the agreement of BURNS and EWOK that the provisions
               of this Section 5 shall be construed by the court in such a
               manner as to impose only those restrictions on BURNS' conduct
               that are reasonable in light of the circumstances and as are
               necessary to assure to EWOK and/or PerBio Science AB the benefits
               provided under Section 5. If, in a judicial proceeding, a court
               shall refuse to enforce all of the separate promises included
               therein because taken together they are more extensive than
               necessary to assure EWOK and/or PerBio Science AB the intended
               benefits of Section 5, it is expressly understood and agreed by
               the parties hereto that the provisions of Section 5 that, if
               eliminated, would permit the remaining separate provisions to be
               enforced in such proceeding shall be deemed eliminated for
               purposes of such proceeding from Section 5.

        6      TERM.

               The initial term of this Agreement is for a period of two (2)
        years, commencing on the "employment date" (as defined in Section 8.2
        below) and terminating two (2) years hence, unless


                                       7







<PAGE>



       sooner terminated pursuant to the provisions of this Agreement. In the
       event that EWOK does not intend to renew this agreement upon the
       completion of its initial term, EWOK shall provide BURNS with a minimum
       of ninety (90) days advance written notice prior to the expiration date
       of this Agreement's initial term; in the event of such advance written
       notice, EWOK may, in its discretion, place BURNS on a leave of absence
       for all or any portion of that ninety (90) day period. Provided, however,
       that the failure to provide the notice required hereunder shall not
       result in the extension of the term of this Agreement unless the parties
       have mutually agreed, in writing, to such an extension.

        7      TERMINATION.

               7.1    Term.

                      The Agreement shall expire upon the expiration of its term
               unless otherwise sooner terminated by the parties' written mutual
               agreement or pursuant to the remaining provisions of this Section
               7.

               7.2    Termination for Cause.

                      EWOK may terminate this Agreement prior to the expiration
               of its term for cause without further obligation to BURNS
               hereunder. For purposes of this Agreement, "for cause" includes
               the following:

              (a)     an intentional act of fraud, embezzlement, theft or any
                      other material violation of the law including those
                      involving dishonesty in connection with BURNS' duties or
                      in the course of her employment with EWOK or the
                      commission of a felony; or

              (b)     intentional wrongful damage to material assets of EWOK; or


                                       8







<PAGE>



               (c)    intentional wrongful disclosure of material confidential
                      information of EWOK;

                      or

               (d)    intentional conduct by BURNS which has resulted or may
                      result in financial loss and legal liability to EWOK which
                      is materially injurious to EWOK.

               No act, or failure to act, on the part of BURNS, shall be deemed
               "intentional" if it was due primarily to an error in judgment or
               negligence, but shall be deemed "intentional" only if done, or
               omitted to be done, by BURNS not in good faith and without
               reasonable belief that her action or omission was in the best
               interests of EWOK. In the event of a termination "for cause"
               under the provisions of this Section 7.2, BURNS shall not be
               entitled to the salary continuation provided in Section 7.6
               below.

               7.3    Termination Without Cause.

                      BURNS may terminate this Agreement upon the provision of
               six (6) months written notice to EWOK. Similarly, EWOK may, in
               its discretion, terminate this Agreement without cause upon the
               provision of six (6) months written notice to BURNS provided that
               EWOK thereafter complies with the applicable provisions of
               Section 7.6 below.

                      In the event of written notice of termination by BURNS or
               EWOK under this Section, EWOK may, in its discretion, place BURNS
               on a leave of absence for all or any portion of that six (6)
               month notice period up to and including the effective date of
               BURNS' termination from employment.

               7.4    Termination Upon Death or Disability.

                      EWOK may terminate this Agreement without further
               obligation to BURNS hereunder upon the death or permanent
               disability of BURNS. For purposes of this Agreement, the
               "permanent disability" of BURNS shall be deemed to occur if the
               Board


                                       9







<PAGE>


               of Directors of EWOK determines, based upon competent
               medical evidence, that BURNS is unable to substantially perform
               the services required of her, hereunder, with or without a
               reasonable accommodation, for a continuous period of ninety (90)
               days or more. BURNS shall cooperate with EWOK in providing
               medical information necessary for EWOK to assess the parties'
               respective duties and obligations under the provisions of this
               Section.

               7.5    Termination by BURNS for "Good Reason"

                      BURNS' employment under this Agreement may be terminated
               for good reason (as set forth below) by written notice from her
               to the Chairman of the Board of Directors of EWOK at least thirty
               (30) days prior to a date of termination subsequent to the
               occurrence of any of the following events:


               (a)    a reasonable determination by BURNS in good faith that
                      there has been a significant adverse change in the nature
                      or scope of BURNS' responsibilities, authorities, powers,
                      functions or duties; or

               (b)    a reduction in BURNS' monetary compensation; or

               (c)    the relocation of BURNS' offices at which BURNS is
                      principally employed to a location more than 50 miles from
                      the location where BURNS is principally employed; or

               (d)    the failure by EWOK to pay to BURNS any portion of her
                      current compensation or the failure by EWOK to continue in
                      effect any material compensation, incentive, bonus or
                      benefit plan in which BURNS participates pursuant to the
                      provisions of this Agreement unless an equitable
                      arrangement (embodied in an ongoing substitute or
                      alternative plan) has been made with respect to such plan,
                      or the failure by EWOK to continue BURNS' participation
                      therein (or in such


                                       10







<PAGE>


                      substitute or alternative plan) on a basis not materially
                      less favorable, both in terms of the amount of benefits
                      provided and the level of BURNS' participation, relative
                      to the other participants.

               The above provisions notwithstanding, "good reason" shall not be
               deemed to exist if any or all of the events noted in this Section
               7.5 have been agreed upon in advance by BURNS and EWOK.

               7.6    Salary Continuation.

                      Subject to the provisions of this Section 7.6, BURNS will
               be provided with salary continuation upon termination of this
               Agreement prior to its term as specified below. If a termination
               during the term of this Agreement occurs pursuant to the
               provisions of Section 7.3 above due to notice of termination
               provided by EWOK, or in the event that this Agreement is not
               renewed and BURNS' employment is terminated at the expiration of
               its initial term (as provided in Section 6 above), BURNS' salary
               (as provided in Section 3.1 above) shall be continued for a
               period of twelve (12) months from the effective date of
               termination; provided, however, that in no event shall BURNS
               receive salary continuation if she has provided notice of
               termination to EWOK pursuant to the provisions of Section 7.3 or
               if the Agreement has been terminated "for cause" as specified in
               Section 7.2 above. Further, in the event of BURNS' termination of
               this Agreement for "good reason" (as specified in Section 7.5
               above), BURNS' salary (as provided in Section 3.1 above) shall be
               continued for a period of twelve (12) months from the effective
               date of termination.

                      The above notwithstanding, BURNS shall not be entitled to
               the salary continuation provided in this Section 7.6 unless and
               until she has signed and delivered to EWOK a binding agreement in
               a form acceptable to EWOK setting forth a release of


                                       11







<PAGE>


               any and all claims arising from her employment, termination from
               employment and termination of this Agreement with EWOK. During
               the period of salary continuation (regardless of duration), BURNS
               shall not be entitled to continuation of the other benefits or
               perquisites provided in this Agreement unless otherwise required
               by law or by the mutual agreement of the parties hereto. Further,
               in no event shall BURNS be entitled to receive multiple payments
               of salary continuation under the provisions of this Section 7.6
               should her termination from employment with EWOK be claimed or
               determined to be attributable, in whole or in part, to two or
               more of the reasons specified in this Section.

               7.7    Property of the Business.

                      Upon BURNS' termination of employment (for any reason),
               all memoranda, notes, lists, records and other documents or
               papers (and all copies thereof) including items stored in
               computer memories, on microfiche or by any other means, made or
               compiled by or on behalf of BURNS, or made available to BURNS
               relating to the business of EWOK, are and shall be EWOK's
               property and shall, if in the possession of BURNS, be promptly
               delivered to EWOK.

        8      MODIFICATION; CONTINGENCIES AND ASSIGNMENT.

               8.1    Modification.

                      This Agreement may not be modified except in writing
               signed by both parties.

               8.2    Contingencies and Assignment.

                      The obligations of BURNS and EWOK under this Agreement are
               contingent upon EWOK's consummation of its merger with
               CORPORATION as set forth below. For purposes of this Agreement,
               the consummation of that merger and BURNS' "employment date"
               shall be deemed to have occurred on the date, if any, on which
               EWOK accepts for


                                       12







<PAGE>


               payment shares tendered pursuant to EWOK's tender offer for all
               of the issued and outstanding common stock of CORPORATION. In the
               event that said contingency is not fully satisfied and the tender
               offer is not consummated, all obligations pursuant to this
               Agreement and the provisions of this Agreement shall be null,
               void and no longer in force or effect.

                      It is expressly agreed that the duties, rights and
               obligations of EWOK and BURNS under this Agreement shall be
               transferred to any entity with which EWOK may merge on or
               following the "employment date" as set forth above. Additionally,
               EWOK or that entity may further assign such duties, rights and
               obligations to other entities following said merger provided said
               assignment is to a subsidiary of PerBio Science AB. EWOK or that
               entity shall provide BURNS with written notice of said
               assignments; in that event, the obligations of BURNS and EWOK as
               set forth in this Agreement shall, thereafter, be applicable to
               the entity identified in that notice. Except as specifically
               provided in this Section 8.2, the duties, rights and obligations
               set forth in this Agreement shall not otherwise be assignable by
               EWOK or BURNS to any other corporation or other entity without
               the other party's approval, in writing.

        9      GOVERNING LAW.

               The performance and interpretation of this Agreement shall be
        construed in accordance with the laws of the State of Massachusetts.

        10     WAIVER.

               Waiver of any breach of the terms and conditions of this
        Agreement shall not be construed to be a waiver of any preceding or
        succeeding breach of the same or different term or condition of this
        Agreement, and this Agreement shall continue and remain in full for and
        effect as if no waiver had occurred.


                                       13







<PAGE>



        11     NOTICE.

               Notices shall be deemed delivered and received as of the date of
        the U.S. Postal Service postmark. Any notice required by this Agreement
        shall be sent by certified mail, return receipt requested, to the
        following addresses:

        To:    EWOK

               c/o Chairman of the Board
               c/o Endogen, Inc.
               30 Commerce Way
               Woburn, MA  01801

               with a copy to:

               Mr. Robb Anderson
               Pierce Chemical Co.
               3747 Meridian Rd.
               Rockford, IL  61101

        To:    CHRISTINE A. BURNS
               9 Salem Road
               Wellesley, MA 02181

        12     SEVERABILITY.

               In the event any of the terms and provisions of this Agreement
        are determined to be invalid or unlawful, the remaining provisions of
        this Agreement will continue in full force and effect to the fullest
        extent permitted by law. The parties expressly agree that a court of
        competent jurisdiction may modify the provisions of this Agreement so as
        to make the Agreement enforceable.

        13     WARRANTY.

               BURNS hereby warrants that neither the entry into this Employment
        Agreement nor its performance by BURNS will conflict with or result in a
        breach of the terms, conditions or


                                       14







<PAGE>


        privileges of any agreement or other obligation of any nature to which
        BURNS is a party, or by which BURNS is bound, including without
        limitation, any employment agreements, non-competition agreements or
        confidentiality agreements previously entered into by BURNS. EXECUTED on
        the 27th day of May, 1999.


EWOK ACQUISITION CORP., a Massachusetts
corporation

By:  /s/ ROBB K. ANDERSON                          /s/ CHRISTINE A. BURNS
Its: President                                   --------------------------
     -------------------------------             CHRISTINE A. BURNS


ATTEST:

   /s/
- ------------------------------------


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