<PAGE>
EXHIBIT 8.1
September 14, 2000
Invitrogen Corporation
1600 Faraday Avenue
Carlsbad, California 92008
Ladies and Gentlemen:
This opinion is being delivered to you for the purpose of satisfying the
requirement of Section 5.2(a) of the Agreement and Plan of Merger dated as of
July 7, 2000 (the "Agreement"), between Invitrogen Corporation, a Delaware
corporation ("Invitrogen"), and Dexter Corporation, a Connecticut corporation
(the "Company").
Pursuant to the Agreement, the Company shall merge with and into Invitrogen, and
the separate corporate existence of the Company shall thereupon cease, and
Invitrogen shall be the surviving corporation in the Merger. Unless otherwise
defined, capitalized terms referred to herein shall have the same meanings as
set forth in the Agreement. All section references, unless otherwise indicated,
are to the Internal Revenue Code of 1986, as amended (the "Code").
We have acted as counsel to Invitrogen in connection with (i) the preparation
and execution of the Agreement, and (ii) the preparation and filing with the
Securities and Exchange Commission under the Securities Act of 1933, as amended,
on August 14, 2000, a Registration Statement on Form S-4 of a Proxy
Statement/Prospectus ("Registration Statement"). As such, and for the purpose of
rendering this opinion, we have examined and are relying upon (without any
independent investigation or review thereof) the truth and accuracy, at all
relevant times, of the statements, covenants, representations and warranties
contained in the following documents (including all schedules and exhibits
thereto): (1) the Agreement; (2) representation letters provided to us by
Invitrogen and the Company in connection with this opinion (the "Officers'
Certificates"); (3) the Registration Statement; and (4) such other instruments
and documents related to the formation, organization and operation of Invitrogen
and the Company or to the consummation of the Merger and the transactions
contemplated thereby as we have deemed necessary or appropriate in order to
enable us to render this opinion.
In connection with rendering this opinion, we have assumed or obtained
representations (and are relying thereon, without any independent investigation
or review thereof) that:
1. Original documents (including signatures) are authentic, documents
submitted to us as copies conform to the original documents, and there has been
(or will be by the Effective Time of the Merger) due execution and delivery of
all documents where due execution and delivery are prerequisites to
effectiveness thereof;
2. Any representation or statement made "to the best of knowledge" or
similarly qualified is correct without such qualification. As to all matters in
which a person or entity making a representation referred to above has
represented that such person or entity either is not a party to, does not have,
or is not aware of, any plan or intention, understanding or agreement, there is
in fact no such plan, intention, understanding or agreement;
<PAGE>
3. All statements, descriptions and representations contained in any of
the documents referred to herein or otherwise made to us (including, but not
limited to the Officers' Certificates) are true and correct as of the date
hereof and at the Effective Time, and no actions have been (or will be) taken
which are inconsistent with such statements, descriptions and representations;
4. The Merger will be consummated in accordance with the terms of the
Agreement (and without any waiver, breach or amendment of any of the material
provisions thereof) and as described in the Registration Statement, will qualify
as a statutory merger under applicable state law, and will be reported by
Invitrogen and the Company on their respective federal income tax returns in a
manner consistent with the opinion set forth below; and
5. An opinion of Skadden, Arps, Slate, Meagher & Flom LLP, counsel to
the Company, dated as of the Effective Time, to the effect that the Merger will
qualify as a reorganization within the meaning of Section 368(a) of the Code,
has been issued to the Company pursuant to Section 5.3(a) of the Agreement and
not withdrawn.
Based on our examination of the foregoing items and subject to the assumptions,
limitations and qualifications set forth herein and in the discussion in the
Proxy Statement/Prospectus included as part of the Registration Statement under
the caption "Material United States Federal Income Tax Consequences of the
Mergers," we are of the opinion that the Merger will qualify as a reorganization
within the meaning of Section 368(a) of the Code. In addition to the
assumptions, limitations and qualifications set forth above, this opinion is
subject to the limitations and qualifications set forth below.
This opinion represents and is based upon our best judgment regarding the
application of federal income tax laws arising under the Code, existing judicial
decisions, administrative regulations and published rulings and procedures. Our
opinion is not binding upon the Internal Revenue Service or the courts, and the
Internal Revenue Service is not precluded from successfully asserting a contrary
position. Furthermore, no assurance can be given that future legislative,
judicial or administrative changes, on either a prospective or retroactive
basis, would not adversely affect the accuracy of the conclusions stated herein.
Nevertheless, we undertake no responsibility to advise you of any new
developments in the application or interpretation of the federal income tax
laws.
No opinion is expressed as to any other matter, including any other tax
consequences of the Merger or any other transaction (including any transaction
undertaken in connection with the Merger) under any foreign, federal, state, or
local tax law.
No opinion is expressed as to any transaction other than the Merger as described
in the Agreement and in the Registration Statement or to any transaction
whatsoever, including the Merger, if all the transactions described in the
Agreement are not consummated in accordance with the terms of such Agreement and
without waiver or breach of any material provision thereof or if all of the
representations, warranties, statements and assumptions upon which we relied are
not true and accurate at all relevant times. In the event any one of the
statements, representations, warranties or assumptions upon which we have relied
to issue this opinion is incorrect, our opinion might be adversely affected and
may not be relied upon.
This opinion has been delivered to you only for the purposes stated. It may not
be relied upon for any other purpose or by any other person or entity, and may
not be made available to any other person or entity without our prior written
consent. We hereby consent, however, to the use of this opinion as an exhibit to
the Registration Statement. By giving this consent, we do not admit that we come
within the category of persons whose consent is required under Section 7 of the
Securities Act or the rules and regulations of the Securities and Exchange
Commission promulgated thereunder (the "Rules"), nor do we hereby admit that we
are experts with respect to any part of the Registration Statement within the
Securities Act or the Rules. By rendering this
<PAGE>
opinion, we undertake no responsibility to update this opinion after the date
hereof for any reason, including but not limited to, any new or changed facts or
law which come to our attention after the date hereof.
Very truly yours,
/s/Gray Cary Ware & Freidenrich LLP
GRAY CARY WARE & FREIDENRICH LLP
