MFS VARIABLE INSURANCE TRUST
497, 1997-05-05
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<PAGE>
 
<TABLE>
<S>                                         <C>
MFS-REGISTERED TRADEMARK- EMERGING GROWTH
SERIES
MFS-REGISTERED TRADEMARK- TOTAL RETURN
SERIES
MFS-REGISTERED TRADEMARK- UTILITIES SERIES
                                            PROSPECTUS
MFS-REGISTERED TRADEMARK- WORLD             May 1,
GOVERNMENTS SERIES                          1997
</TABLE>
 
- --------------------------------------------------------------------------------
 
<TABLE>
<S>                                                              <C>          <S>                                      <C>
MFS-Registered Trademark- VARIABLE INSURANCE TRUST-SM-
</TABLE>
 
MFS  Variable Insurance Trust (the "Trust") is an open-end management investment
company offering insurance company separate  accounts a selection of  investment
vehicles  for  variable  annuity  and  variable  life  insurance  contracts (the
"Contracts"). Currently the  Trust offers  shares of beneficial  interest of  12
separate  mutual fund series (individually  or collectively hereinafter referred
to as a "Series"  or the "Series";  four of which are  offered pursuant to  this
Prospectus).
 
- -- MFS  EMERGING GROWTH  SERIES (the "Emerging  Growth Series"),  which seeks to
   provide long-term growth of capital;
 
- -- MFS TOTAL RETURN SERIES (the "Total Return Series"), which seeks primarily to
   provide above-average income  (compared to a  portfolio invested entirely  in
   equity  securities)  consistent with  the prudent  employment of  capital and
   secondarily to provide  a reasonable  opportunity for growth  of capital  and
   income;
 
- -- MFS UTILITIES SERIES (the "Utilities Series"), which seeks capital growth and
   current  income  (income  above  that  available  from  a  portfolio invested
   entirely in equity securities); and
 
- -- MFS WORLD GOVERNMENTS  SERIES (the "World  Governments Series"), which  seeks
   not  only preservation  but also  growth of  capital, together  with moderate
   current income.
                              -------------------
 
THE EMERGING GROWTH  SERIES IS  INTENDED FOR  INVESTORS WHO  UNDERSTAND AND  ARE
WILLING  TO ACCEPT  THE RISKS ENTAILED  IN SEEKING LONG-TERM  GROWTH OF CAPITAL.
BECAUSE  OF  THEIR   INVESTMENT  POLICIES  PERMITTING   INVESTMENT  IN   FOREIGN
SECURITIES, INVESTMENTS IN THE SERIES MAY BE SUBJECT TO A GREATER DEGREE OF RISK
THAN INVESTMENTS IN OTHER INVESTMENT COMPANIES WHICH INVEST ENTIRELY IN DOMESTIC
SECURITIES.
                              -------------------
 
  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
    EXCHANGE  COMMISSION  OR ANY  STATE SECURITIES  COMMISSION NOR  HAS THE
     SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION
       PASSED UPON  THE ACCURACY  OR ADEQUACY  OF THIS  PROSPECTUS.  ANY
             REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.
                              -------------------
 
SHARES  OF THE TRUST  ARE AVAILABLE AND  ARE BEING MARKETED  AS A POOLED FUNDING
VEHICLE FOR LIFE INSURANCE COMPANIES WRITING ALL TYPES OF CONTRACTS.
 
This Prospectus sets forth  concisely the information about  each Series that  a
prospective  investor should know  before applying for  the Contracts offered by
the separate accounts of  certain insurance companies ("Participating  Insurance
Companies").  Investors are advised  to read this  Prospectus and the applicable
Contract prospectus  carefully and  retain  them for  future reference.  If  you
require  more detailed information, a  Statement of Additional Information dated
May 1,  1997, as  amended or  supplemented from  time to  time (the  "SAI"),  is
available  upon request  without charge  and may  be obtained  by calling  or by
writing to the Shareholder Servicing Agent (see back cover for address and phone
number). The SAI, which is incorporated  by reference into this Prospectus,  has
been  filed with  the Securities  and Exchange  Commission (the  "SEC"). The SEC
maintains an Internet World Wide Web site that contains the SAI, materials  that
are  incorporated  by reference  into  this Prospectus  and  the SAI,  and other
information regarding the Series. This Prospectus is available on the  Adviser's
Internet World Wide Web site at http://www.mfs.com.
 
   INVESTORS SHOULD READ THIS PROSPECTUS AND RETAIN IT FOR FUTURE REFERENCE.
<PAGE>
TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                                                       PAGE
                                                                                                       ---
  <S>                                                                                                  <C>
  1.  Expense Summary................................................................................   3
  2.  Investment Concept of the Trust................................................................   3
  3.  Condensed Financial Information................................................................   5
  4.  Investment Objectives and Policies.............................................................   9
          MFS Emerging Growth Series.................................................................   9
          MFS Total Return Series....................................................................   9
          MFS Utilities Series.......................................................................  10
          MFS World Governments Series...............................................................  11
  5.  Investment Techniques..........................................................................  12
  6.  Additional Risk Factors........................................................................  19
  7.  Management of the Series.......................................................................  21
  8.  Information Concerning Shares of Each Series...................................................  24
          Purchases and Redemptions..................................................................  24
          Net Asset Value............................................................................  24
          Distributions..............................................................................  24
          Tax Status.................................................................................  24
          Description of Shares, Voting Rights and Liabilities.......................................  25
          Performance Information....................................................................  25
          Expenses...................................................................................  26
          Shareholder Communications.................................................................  26
  Appendix A -- Description of Bond Ratings..........................................................  A-1
  Appendix B -- Principal Sectors of the Utilities Industry..........................................  B-1
</TABLE>
 
                                       2
<PAGE>
1.  EXPENSE SUMMARY
 
ANNUAL OPERATING EXPENSES (AS A PERCENTAGE OF AVERAGE NET ASSETS):
 
<TABLE>
<CAPTION>
                                                                MFS        MFS                   MFS
                                                              EMERGING    TOTAL       MFS       WORLD
                                                               GROWTH     RETURN    UTILITIES  GOVERNMENTS
                                                               SERIES     SERIES     SERIES     SERIES
                                                              --------   --------   --------   --------
<S>                                                           <C>        <C>        <C>        <C>
Management Fee..............................................  0.75%      0.75%      0.75%      0.75%
Other Expenses (after expense limitation)(1)(2).............  0.25%      0.25%      0.25%      0.25%
                                                              --------    ---        ---       --------
Total Operating Expenses (after expense limitation)(2)......  1.00%      1.00%      1.00%      1.00%
</TABLE>
 
- ------------------------
(1) Each  Series has  an expense  offset arrangement  which reduces  the Series'
    custodian fee based upon  the amount of cash  maintained by the Series  with
    its  custodian and dividend disbursing agent,  and may enter into other such
    arrangements and directed brokerage arrangements (which would also have  the
    effect  of reducing the  Series' expenses). Any such  fee reductions are not
    reflected under "Other Expenses."
(2) The Adviser  has  agreed  to  bear expenses  for  each  Series,  subject  to
    reimbursement  by each Series, such that each Series' "Other Expenses" shall
    not exceed 0.25% of the  average daily net assets  of the Series during  the
    current  fiscal year.  See "Information  Concerning Shares  of Each Series--
    Expenses." Otherwise, "Other  Expenses" and "Total  Operating Expenses"  for
    each Series would be:
 
<TABLE>
<CAPTION>
                                                                          "TOTAL
                                                               "OTHER    OPERATING
                                                              EXPENSES"  EXPENSES"
                                                              WITHOUT    WITHOUT
                                                              EXPENSE    EXPENSE
SERIES                                                        LIMITATION LIMITATION
- ------------------------------------------------------------  --------   --------
<S>                                                           <C>        <C>
Emerging Growth.............................................  0.41%      1.16%
Total Return................................................  1.35%      2.10%
Utilities...................................................  2.00%      2.75%
World Governments...........................................  1.28%      2.03%
</TABLE>
 
    The   purpose  of  the  expense  table  above  is  to  assist  investors  in
understanding the various costs  and expenses that a  shareholder of the  Series
will  bear directly or indirectly. The  Series' annual operating expenses do not
reflect  expenses  imposed  by  separate  accounts  of  Participating  Insurance
Companies  through which  an investment  in a  Series is  made or  their related
Contracts. A separate account's expenses are disclosed in the prospectus through
which the Contract relating to that separate account is offered for sale.
 
2.  INVESTMENT CONCEPT OF THE TRUST
 
    The Trust is an open-end, registered management investment company comprised
of the following twelve series:  Emerging Growth Series, Value Series,  Research
Series,  Growth With Income Series, Total  Return Series, Utilities Series, High
Income Series, World  Governments Series,  Strategic Fixed  Income Series,  Bond
Series,  Limited  Maturity Series  and  Money Market  Series.  Each Series  is a
segregated, separately  managed  portfolio of  securities.  All of  the  Series,
except the Utilities Series, World Governments Series and Strategic Fixed Income
Series, are diversified. Additional series may be created from time to time. The
Trust  was organized as a  business trust under the  laws of The Commonwealth of
Massachusetts by a Declaration of Trust dated February 1, 1994.
 
    The Trust  currently  offers shares  of  each Series  to  insurance  company
separate  accounts that fund Contracts. Separate accounts may purchase or redeem
shares at  net asset  value without  any sales  or redemption  charge. Fees  and
charges imposed by a separate account, however, will affect the actual return to
the   holder  of  a  Contract.  A  separate  account  may  also  impose  certain
restrictions or limitations on the  allocation of purchase payments or  Contract
value  to one or more Series, and not  all Series may be available in connection
with a particular Contract. Prospective investors should consult the  applicable
Contract  prospectus for information regarding fees and expenses of the Contract
and separate account and any  applicable restrictions or limitations. The  Trust
assumes no responsibility for such prospectuses.
 
    Shares  of the Series are offered  to the separate accounts of Participating
Insurance Companies  that are  affiliated  or unaffiliated  ("shared  funding").
Shares  of the Series may serve as  the underlying investments for both variable
annuity  and  variable  life  insurance  contracts  ("mixed  funding").  Due  to
differences  in tax treatment or other  considerations, the interests of various
Contract owners might at some time be in conflict. The Trust currently does  not
foresee  any such conflict. Nevertheless, the Trust's Trustees intend to monitor
events in  order to  identify any  material irreconcilable  conflicts which  may
possibly arise and to determine what action, if any, should be taken in response
thereto.  If such a conflict were to occur, one or more separate accounts of the
Participating Insurance Companies might be required to withdraw its  investments
in  one  or  more  Series. This  might  force  a Series  to  sell  securities at
disadvantageous prices.
 
                                       3
<PAGE>
    Individual Contract holders are not the "shareholders" of the Trust. Rather,
the Participating  Insurance  Companies  and their  separate  accounts  are  the
shareholders  or  investors, although  such  companies may  pass  through voting
rights to their Contract holders.
 
    The Trust's Board of Trustees provides broad supervision over the affairs of
the Trust and the Series.  Massachusetts Financial Services Company, a  Delaware
corporation  ("MFS" or the "Adviser"), is the investment adviser to each Series.
A majority of the Trustees of the Trust are not affiliated with the Adviser. The
Adviser is responsible for the management of  the assets of each Series and  the
officers  of the Trust  are responsible for the  operations. The Adviser manages
the Series'  portfolios  from day  to  day  in accordance  with  the  investment
objectives and policies of each Series. The selection of investments and the way
they  are managed  depend on the  conditions and  trends in the  economy and the
financial marketplaces.
 
                                       4
<PAGE>
3.  CONDENSED FINANCIAL INFORMATION
 
The following financial information (presented  for each Series which  commenced
investment  operations prior  to December 31,  1996) has been  audited since the
commencement of  investment operations  of such  Series and  should be  read  in
conjunction with the financial statements included in the Series' Annual Reports
to  Shareholders. These financial statements  are incorporated by reference into
the SAI in reliance  upon the report of  the Series' independent auditors  given
upon  their authority as experts in accounting and auditing. The Series' current
independent auditors are Deloitte & Touche LLP.
 
                             EMERGING GROWTH SERIES
 
<TABLE>
<CAPTION>
                                                                      YEAR ENDED          PERIOD ENDED
                                                                   DECEMBER 31, 1996   DECEMBER 31, 1995*
                                                                   -----------------   ------------------
<S>                                                                <C>                 <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................      $  11.41             $10.00
                                                                       --------             ------
Income from investment operations#--
  Net investment income (loss)Section............................      $  (0.01)            $ 0.01
  Net realized  and unrealized  gain on  investments and  foreign
    currency transactions........................................          1.95               1.74
                                                                       --------             ------
    Total from investment operations.............................      $   1.94             $ 1.75
                                                                       --------             ------
Less distributions declared to shareholders--
  From net investment income.....................................      $     --             $(0.01)
  From  net  realized gain  on  investments and  foreign currency
    transactions.................................................         (0.06)             (0.26)
  In excess  of  net realized  gain  on investments  and  foreign
    currency transactions........................................         (0.05)                --
  Tax return of capital..........................................            --              (0.07)
                                                                       --------             ------
    Total distributions declared to shareholders.................      $  (0.11)            $(0.34)
                                                                       --------             ------
Net asset value--end of period...................................      $  13.24             $11.41
                                                                       --------             ------
                                                                       --------             ------
Total return.....................................................         17.02%             17.41%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................          1.00%              1.00%+
  Net investment income (loss)...................................         (0.08)%             0.10%+
Portfolio turnover...............................................            96%                73%
Average commission rate###.......................................      $ 0.0401                 --
Net assets at end of period (000 omitted)........................      $104,956             $3,869
<FN>
- ------------------------
        *  For the period from the commencement of investment operations, July 24, 1995 to December 31, 1995.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
      ###  Average commission rate is calculated for Series' with fiscal years beginning on or after September 1, 1995.
  Section  The Adviser voluntarily agreed to maintain the expenses of the Series at not more than 1.00% of average daily
           net  assets. To the extent actual expenses were over these limitations, the net investment loss per share and
           the ratios would have been:
 
Net investment loss..............................................         $(0.03)           $(0.18)
Ratios (to average net assets):
  Expenses.......................................................           1.16%             2.91%+
  Net investment loss............................................          (0.23)%           (1.78)%+
</TABLE>
 
                                       5
<PAGE>
                              TOTAL RETURN SERIES
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED           PERIOD ENDED
                                                                    DECEMBER 31, 1996    DECEMBER 31, 1995*
                                                                   -------------------   ------------------
<S>                                                                <C>                   <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................        $ 12.25               $10.00
                                                                         -------               ------
Income from investment operations#--
  Net investment incomeSection...................................        $  0.46               $ 0.41
  Net realized and unrealized gain on investments and foreign
    currency transactions........................................           1.30                 2.32
                                                                         -------               ------
    Total from investment operations.............................        $  1.76               $ 2.73
                                                                         -------               ------
Less distributions declared to shareholders--
  From net investment income.....................................        $ (0.21)              $(0.25)
  From net realized gain on investments and foreign currency
    transactions.................................................          (0.09)               (0.23)
                                                                         -------               ------
    Total distributions declared to shareholders.................        $ (0.30)              $(0.48)
                                                                         -------
Net asset value--end of period...................................        $ 13.71               $12.25
                                                                         -------               ------
                                                                         -------               ------
Total return.....................................................          14.37%               27.34%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................           1.00%                1.00%+
  Net investment income..........................................           3.59%                3.83%+
Portfolio turnover...............................................             76%                  16%
Average commission rate###.......................................        $0.0485                   --
Net assets at end of period (000 omitted)........................        $19,250               $2,797
<FN>
- ------------------------
        *  For the period from the commencement of investment operations, January 3, 1995 to December 31, 1995.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
      ###  Average commission rate is calculated for funds with fiscal years beginning on or after September 1, 1995.
  Section  The Adviser voluntarily agreed to maintain the expenses of the Series at not more than 1.00% of average daily
           net assets. To the extent actual  expenses were over these limitations,  the net investment income per  share
           and the ratios would have been:
 
Net investment income............................................            $0.32             $0.22
Ratios (to average net assets):
  Expenses.......................................................             2.10%             2.49%+
  Net investment income..........................................             2.49%             2.09%+
</TABLE>
 
                                       6
<PAGE>
                                UTILITIES SERIES
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED           PERIOD ENDED
                                                                    DECEMBER 31, 1996    DECEMBER 31, 1995*
                                                                   -------------------   ------------------
<S>                                                                <C>                   <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................        $ 12.57               $10.00
                                                                         -------               ------
Income from investment operations#--
  Net investment incomeSection...................................        $  0.55               $ 0.39
  Net realized and unrealized gain on investments and foreign
    currency transactions........................................           1.78                 3.00
                                                                         -------               ------
    Total from investment operations.............................        $  2.33               $ 3.39
                                                                         -------               ------
Less distributions declared to shareholders--
  From net investment income.....................................        $ (0.35)              $(0.24)
  From net realized gain on investments and foreign currency
    transactions.................................................          (0.88)               (0.58)
  In excess of realized gain on investments and foreign currency
    transactions.................................................          (0.01)                  --
                                                                         -------               ------
    Total distributions declared to shareholders.................        $ (1.24)              $(0.82)
                                                                         -------
Net asset value--end of period...................................        $ 13.66               $12.57
                                                                         -------               ------
                                                                         -------               ------
Total return.....................................................          18.51%               33.94%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................           1.00%                1.00%+
  Net investment income..........................................           4.19%                3.66%+
Portfolio turnover...............................................            121%                  94%
Average commission rate###.......................................        $0.0416                   --
Net assets at end of period (000 omitted)........................        $ 9,572               $2,373
<FN>
- ------------------------
        *  For the period from the commencement of investment operations, January 3, 1995 to December 31, 1995.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
      ###  Average commission rate is calculated for funds with fiscal years beginning on or after September 1, 1995.
  Section  The Adviser voluntarily agreed to maintain the expenses of the Series at not more than 1.00% of average daily
           net  assets. To the extent actual  expenses were over these limitations,  the net investment income per share
           and the ratios would have been:
 
Net investment income............................................            $0.32             $0.17
Ratios (to average net assets):
  Expenses.......................................................             2.75%             3.08%+
  Net investment income..........................................             2.44%             1.62%+
</TABLE>
 
                                       7
<PAGE>
                            WORLD GOVERNMENTS SERIES
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED            YEAR ENDED          PERIOD ENDED
                                                                    DECEMBER 31, 1996    DECEMBER 31, 1995    DECEMBER 31, 1994*
                                                                   -------------------   ------------------   ------------------
<S>                                                                <C>                   <C>                  <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................        $ 10.17               $ 9.82               $10.00
                                                                         -------               ------               ------
Income from investment operations#--
  Net investment incomeSection...................................        $  0.60               $ 0.63               $ 0.17
  Net realized and unrealized gain (loss) on investments and
    foreign currency transactions................................          (0.19)                0.78                (0.09)
                                                                         -------               ------               ------
    Total from investment operations.............................        $  0.41               $ 1.41               $ 0.08
                                                                         -------               ------               ------
Less distributions declared to shareholders--
  From net investment income.....................................             --               $(0.42)              $(0.17)
  In excess of net investment income.............................             --                (0.54)               (0.09)
  Tax return of capital..........................................             --                (0.10)                  --
                                                                         -------               ------               ------
    Total distributions declared to shareholders.................             --               $(1.06)              $(0.26)
                                                                         -------               ------               ------
Net asset value--end of period...................................        $ 10.58               $10.17               $ 9.82
                                                                         -------               ------               ------
                                                                         -------               ------               ------
Total return.....................................................           4.03%               14.38%                0.79%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................           1.00%                1.00%                1.00%+
  Net investment income..........................................           5.84%                6.05%                4.68%+
Portfolio turnover...............................................            361%                 211%                  62%
Net assets at end of period (000 omitted)........................        $26,023               $7,424               $2,881
<FN>
- ------------------------
        *  For the period from the commencement of investment operations, June 14, 1994 to December 31, 1994.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
  Section  The Adviser voluntarily agreed to maintain the expenses of the Series at not more than 1.00% of average daily
           net assets. To the extent actual  expenses were over these limitations,  the net investment income per  share
           and the ratios would have been:
 
Net investment income............................................            $0.50              $0.53               $0.16
Ratios (to average net assets):
  Expenses.......................................................             2.03%              1.99%               1.10%+
  Net investment income..........................................             4.81%              5.09%               4.58%+
</TABLE>
 
                                       8
<PAGE>
4.  INVESTMENT OBJECTIVES AND POLICIES
 
    Each  Series has  different investment  objectives which  it pursues through
separate investment policies, as described below. The differences in  objectives
and policies among the Series can be expected to affect the degree of market and
financial  risk to which each  Series is subject and  the return of each Series.
The investment  objectives and  policies of  each Series  may, unless  otherwise
specifically  stated, be changed by the Trustees  of the Trust without a vote of
the shareholders. Any investment  involves risk and there  is no assurance  that
the objectives of any Series will be achieved.
 
    In  addition  to the  specific  investment practices  described  below, each
Series may also engage in certain  investment techniques as described under  the
caption  "Investment  Techniques"  below  and  in  the  SAI  under  the  caption
"Investment Techniques." The Series' investments  are subject to certain  risks,
as described in the above-referenced sections of this Prospectus and the SAI and
as described below under the caption "Additional Risk Factors."
 
MFS  EMERGING GROWTH SERIES --  The Series seeks to  provide long-term growth of
capital. Dividend  and interest  income from  portfolio securities,  if any,  is
incidental to the Series' investment objective of long-term growth of capital.
 
    The  Series' policy is to invest primarily (I.E., at least 80% of its assets
under normal circumstances) in common stocks of companies that MFS believes  are
early  in  their  life  cycle  but which  have  the  potential  to  become major
enterprises (emerging  growth  companies).  Such companies  generally  would  be
expected to show earnings growth over time that is well above the growth rate of
the  overall economy  and the  rate of inflation,  and would  have the products,
technologies, management and  market and other  opportunities which are  usually
necessary  to become more widely recognized as growth companies. Emerging growth
companies can  be of  any size,  and the  Series may  invest in  larger or  more
established  companies whose rates of earnings growth are expected to accelerate
because of  special  factors,  such as  rejuvenated  management,  new  products,
changes  in consumer demand, or basic changes in the economic environment. While
the Series will invest primarily in common stocks, the Series may, to a  limited
extent,  seek appreciation  in other  types of  securities such  as fixed income
securities (which  may be  unrated), convertible  securities and  warrants  when
relative  values  make such  purchases  appear attractive  either  as individual
issues or as types  of securities in certain  economic environments. The  Series
may   invest  in  non-convertible  fixed  income  securities  rated  lower  than
"investment grade"  (rated  Ba  or  lower by  Moody's  Investors  Service,  Inc.
("Moody's")  or BB  or lower  by Standard &  Poor's Ratings  Services ("S&P") or
Fitch Investors Service, Inc. ("Fitch")) (commonly known as "junk bonds") or  in
comparable  unrated securities,  when, in  the opinion  of the  Adviser, such an
investment presents a greater opportunity for appreciation with comparable  risk
to   an  investment  in  "investment  grade"  securities.  Under  normal  market
conditions, the Series will invest not more  than 5% of its net assets in  these
securities.  For  a  description  of  these  ratings,  see  Appendix  A  to this
Prospectus.
 
    The nature of investing in  emerging growth companies involves greater  risk
than  is customarily associated with  investments in more established companies.
Emerging growth companies often have limited product lines, markets or financial
resources, and  they may  be dependent  on one-person  management. In  addition,
there  may be less research  available on many promising  small and medium sized
emerging growth companies, making  it more difficult to  find and analyze  these
companies.  The  securities  of  emerging  growth  companies  may  have  limited
marketability and may be subject to more abrupt or erratic market movements than
securities of larger, more established  growth companies or the market  averages
in  general. Shares of the Series, therefore, are subject to greater fluctuation
in value than shares  of a conservative  equity fund or of  a growth fund  which
invests entirely in proven growth stocks.
 
    Consistent  with its investment objective  and policies described above, the
Series may also invest up to 25% (and generally expects to invest not more  than
15%)  of  its  net  assets  in  foreign  securities  (including  emerging market
securities and Brady Bonds) which are not traded on a U.S. exchange.
 
MFS TOTAL RETURN SERIES -- The Total Return Series' primary investment objective
is to provide above-average income (compared to a portfolio invested entirely in
equity securities) consistent with  the prudent employment  of capital, and  its
secondary objective is to provide a reasonable opportunity for growth of capital
and  income, since many securities offering a better than average yield may also
possess growth potential. Thus, in  selecting securities for its portfolio,  the
Series  considers each of  these objectives. Under  normal market conditions, at
least 25% of the Total Return Series' assets will be invested in non-convertible
fixed income securities, and at  least 40% and no more  than 75% of the  Series'
assets  will be  invested in equity  securities. Equity securities  in which the
Series may invest include the following: common
 
                                       9
<PAGE>
stocks, preferred  stocks  and  preference stocks;  securities  such  as  bonds,
warrants or rights that are convertible into stocks; and depositary receipts for
those securities. These securities may be listed on securities exchanges, traded
in various over-the-counter markets or have no organized markets.
 
    The  Series' policy is  to invest in  a broad list  of securities, including
short-term obligations. The list  may be diversified not  only by companies  and
industries,  but also by type of security.  The Total Return Series may vary the
percentage of assets invested in any one type of security in accordance with the
Adviser's interpretation of  economic and  money market  conditions, fiscal  and
monetary  policy  and underlying  security  values. The  Series' non-convertible
fixed income  investments  may consist  of  both "investment  grade"  securities
(rated  Baa  or better  by Moody's  or BBB  or better  by S&P  or by  Fitch) and
securities that are unrated or are in  the lower rating categories (rated Ba  or
lower  by Moody's or  BB or lower by  S&P or by Fitch)  (commonly known as "junk
bonds") including  up to  20%  of its  assets  in non-convertible  fixed  income
securities  that are  in these  lower rating  categories and  comparable unrated
securities (see "Additional Risk Factors" below). Generally, most of the Series'
long-term non-convertible fixed income  investments will consist of  "investment
grade"  securities. See Appendix A to this Prospectus for a description of these
ratings.
 
    The  Series  may  also  invest  in  United  States  government   securities,
including:  (1) U.S. Treasury  obligations, which differ  only in their interest
rates, maturities and times of issuance: U.S. Treasury bills (maturities of  one
year  or less); U.S. Treasury  notes (maturities of one  to ten years); and U.S.
Treasury bonds (generally maturities  of greater than ten  years), all of  which
are  backed  by  the full  faith  and credit  of  the U.S.  Government;  and (2)
obligations issued or  guaranteed by  U.S. Government  agencies, authorities  or
instrumentalities,  some of which are backed by the full faith and credit of the
U.S. Treasury, E.G., direct pass-through certificates of the Government National
Mortgage Association ("GNMA"); some of which  are supported by the right of  the
issuer  to borrow  from the U.S.  Government, E.G., obligations  of Federal Home
Loan Banks;  and some  of which  are backed  only by  the credit  of the  issuer
itself,   E.G.,   obligations  of   the   Student  Loan   Marketing  Association
(collectively,  "U.S.  Government  Securities").   The  term  "U.S.   Government
Securities"  also includes  interests in  trusts or  other entities representing
interests in obligations that  are backed by  the full faith  and credit of  the
U.S.  Government  or  are  issued  or guaranteed  by  the  U.S.  Government, its
agencies, authorities or instrumentalities.
 
    Consistent with its investment objective  and policies described above,  the
Series  may  also invest  up  to 20%  of its  net  assets in  foreign securities
(including emerging market securities and Brady Bonds) which are not traded on a
U.S. exchange.
 
MFS UTILITIES SERIES --  The Utilities Series' investment  objective is to  seek
capital  growth and current income (income above that available from a portfolio
invested entirely in equity securities).
 
    The Utilities Series will seek to achieve its objective by investing,  under
normal  circumstances, at  least 65% (but  up to  100% at the  discretion of the
Adviser) of  its assets  in equity  and  debt securities  of both  domestic  and
foreign  companies in  the utilities  industry. Equity  securities in  which the
Series may invest  include the  following: common stocks;  preferred stocks  and
preference  stocks;  securities  such  as bonds,  warrants  or  rights  that are
convertible into stocks;  and depositary  receipts for  those securities.  These
securities   may  be   listed  on   securities  exchanges,   traded  in  various
over-the-counter markets  or have  no organized  markets. At  least 80%  of  the
non-convertible  fixed income securities held by the Series will be rated at the
time of investment at least Baa by Moody's or BBB by S&P or by Fitch or will  be
of  comparable  quality  as  determined by  the  Adviser  (see  "Additional Risk
Factors" below). See Appendix  A to this Prospectus  for a description of  these
ratings.  The Series may also invest in debt and equity securities of issuers in
other industries, as  discussed below, although  under normal circumstances  not
more than 35% of the Series' assets will be so invested. In addition, the Series
may hold a portion of its assets in cash and money market instruments.
 
    Companies  in the  utilities industry include  (i) companies  engaged in the
manufacture, production,  generation,  transmission,  sale  or  distribution  of
electric,  gas or other  types of energy,  water or other  sanitary services and
(ii) companies  engaged  in telecommunications,  including  telephone,  cellular
telephones,   telegraph,  satellite,  microwave,   cable  television  and  other
communications media (but  not companies  engaged in  public broadcasting).  The
Adviser  deems a particular company  to be in the  utilities industry if, at the
time of investment, the  Adviser determines that at  least 50% of the  company's
assets or revenues are derived from one or more of those industries. The portion
of  the Utilities Series' assets invested in a particular type of utility and in
equity or  debt securities  will vary  in light  of changes  in interest  rates,
market  conditions  and  economic  conditions  and  other  factors.  For further
information on the  principal sectors  of the  utilities industry  in which  the
Series may invest, see Appendix B to this Prospectus.
 
                                       10
<PAGE>
    Consistent  with its investment objective  and policies described above, the
Series may  also invest  up  to 35%  of its  net  assets in  foreign  securities
(including emerging market securities and Brady Bonds) which are not traded on a
U.S. exchange.
 
    Since   the  Utilities  Series'  investments  are  concentrated  in  utility
securities, the  value of  the Series'  shares will  be especially  affected  by
factors  peculiar to the utilities industry,  and may fluctuate more widely than
the value of shares of a fund that invests in a broader range of industries. The
rates many  utility  companies may  charge  their customers  are  controlled  by
governmental  regulatory commissions which may result  in a delay in the utility
company passing along increases in costs to its customers. Furthermore, there is
no assurance  that  regulatory  authorities  will, in  the  future,  grant  rate
increases  or that  such increases  will be  adequate to  permit the  payment of
dividends on common stocks. Many utility companies, especially electric and  gas
and   other   energy  related   utility  companies,   are  subject   to  various
uncertainties, including: risks of increases in fuel and other operating  costs;
the  high cost of borrowing to  finance capital construction during inflationary
periods; difficulty  obtaining adequate  returns on  invested capital,  even  if
frequent rate increases are approved by public service commissions; restrictions
on  operations and increased costs  and delays as a  result of environmental and
nuclear safety regulations; securing  financing for large construction  projects
during  an inflationary period; difficulties of the capital markets in absorbing
utility debt and equity  securities; difficulty in  raising capital in  adequate
amounts  on reasonable terms in periods  of high inflation and unsettled capital
markets; technological innovations which  may render existing plants,  equipment
or  products obsolete;  the potential impact  of natural  or man-made disasters;
difficulties in obtaining natural gas for resale or fuel for electric generation
at reasonable prices; coping  with the general  effects of energy  conservation,
particularly  in light of changing policies  regarding energy; and special risks
associated with  the  construction and  operation  of nuclear  power  generating
facilities,  including  technical factors  and costs,  and the  possibility that
federal, state and municipal government authorities may from time to time review
existing  requirements  and  impose  additional  requirements.  Certain  utility
companies,  especially gas and telephone utility companies, have in recent years
been affected  by  increased  competition,  which  could  adversely  affect  the
profitability  of such  utility companies. Furthermore,  there are uncertainties
resulting from certain  telecommunications companies'  diversification into  new
domestic  and  international  businesses  as well  as  agreements  by  many such
companies linking  future  rate increases  to  inflation or  other  factors  not
directly related to the active operating profits of the enterprise.
 
    Foreign  utility  companies are  also subject  to regulation,  although such
regulations may or may not be comparable to those in the United States.  Foreign
utility  companies may be more heavily regulated by their respective governments
than utilities in the U.S. and, as  in the U.S., generally are required to  seek
government  approval  for  rate  increases.  In  addition,  since  many  foreign
utilities use fuel that causes more pollution than those used in the U.S.,  such
utilities  may be required to invest in  pollution control equipment to meet any
proposed pollution restrictions. Foreign regulatory systems vary from country to
country and may evolve in ways different from regulation in the U.S.
 
    The Utilities Series is  permitted to invest in  securities of issuers  that
are outside the utilities industry, although under normal circumstances not more
than 35% of the Series' assets will be so invested. Such investments may include
common  stocks,  debt  securities  (including  municipal  debt  securities)  and
preferred stocks and will be selected  to meet the Series' investment  objective
of  both capital growth  and current income.  These securities may  be issued by
either U.S. or non-U.S.  companies. Some of these  issuers may be in  industries
related  to the  utilities industry  and, therefore,  may be  subject to similar
risks.
 
    Investments outside the utilities industry may also include U.S.  Government
Securities,   as  that  term   is  defined  under   "Investment  Objectives  and
Policies--MFS Total Return Series" above. When and if available, U.S. Government
Securities may be purchased at a  discount from face value. However, the  Series
does not intend to hold such securities to maturity for the purpose of achieving
potential  capital  gains,  unless  current  yields  on  the  securities  remain
attractive.
 
MFS WORLD  GOVERNMENTS  SERIES  --  The  World  Governments  Series'  investment
objective  is to seek not only preservation but also growth of capital, together
with moderate current income.
 
    The World  Governments  Series seeks  to  achieve its  investment  objective
through   a  professionally   managed,  internationally   diversified  portfolio
consisting  primarily  of  debt  securities  and  to  a  lesser  extent   equity
securities.  The Series  attempts to  provide investors  with an  opportunity to
enhance the  value  and increase  the  protection of  their  investment  against
inflation  and otherwise by taking advantage  of investment opportunities in the
U.S. as well as in other countries where opportunities may be more rewarding. It
is believed that diversification of  assets on an international basis  decreases
the  degree to which events  in any one country,  including the U.S., can affect
the entire portfolio. Although the percentage of the Series' assets invested  in
securities  issued  abroad  and  denominated  in  foreign  currencies  will vary
 
                                       11
<PAGE>
depending on the state of the economies of the principal countries of the world,
their financial markets  and the relationship  of their currencies  to the  U.S.
dollar,  under  normal  conditions  the  Series'  portfolio  is  internationally
diversified. However,  for  temporary  defensive  reasons  or  during  times  of
international  political or economic uncertainty or  turmoil, most or all of the
Series' investments may be in the U.S.
 
    Under normal economic  and market conditions,  at least 80%  of the  Series'
portfolio  is invested in  debt securities, such  as bonds, debentures, mortgage
securities, notes,  commercial  paper, obligations  issued  or guaranteed  by  a
government  or any of its political subdivisions, agencies or instrumentalities,
certificates of deposit, as well  as debt obligations which  may have a call  on
common stock by means of a conversion privilege or attached warrants.
 
    Consistent  with its investment objective  and policies described above, the
Series may invest up to 100% (and generally expects to invest not more than 80%)
of its net assets  in foreign securities  (including emerging market  securities
and  Brady  Bonds)  which  are  not traded  on  a  U.S.  exchange.  Although the
percentage of the Series'  assets invested in foreign  securities will vary,  at
least  65% of the  Series' assets will  be invested in  at least three different
countries, one of which may be the  U.S., except when the Adviser believes  that
investing  for  temporary defensive  purposes is  appropriate. The  Adviser will
determine the amount of the World  Governments Series' assets to be invested  in
the  U.S. and the amount to be invested abroad. The U.S. assets will be invested
in high  quality  debt  securities and  the  remainder  of the  assets  will  be
diversified among countries where opportunities for total return are expected to
be  most attractive.  It is currently  expected that  investments within foreign
countries will be primarily in  government securities to minimize credit  risks.
The  Series  will not  invest 25%  or more  of the  value of  its assets  in the
securities of any one foreign government. The portfolio will be managed actively
and the asset allocations modified as the Adviser deems necessary.
 
    The World Governments Series will purchase non-dollar securities denominated
in the currency of countries where the interest rate environment as well as  the
general economic climate provide an opportunity for declining interest rates and
currency  appreciation. If  interest rates  decline, such  non-dollar securities
will appreciate in value. If the  currency also appreciates against the  dollar,
the  total investment in  such non-dollar securities  would be enhanced further.
Conversely, a rise in interest rates or decline in currency exchange rates would
adversely affect  the  Series'  return. Investments  in  non-dollar  denominated
securities  are evaluated  primarily on  the strength  of a  particular currency
against the dollar and on the interest rate climate of that country. Currency is
judged on the basis of  fundamental economic criteria (E.G., relative  inflation
levels  and  trends,  growth rate  forecasts,  balance of  payments  status, and
economic policies) as well as technical  and political data. In addition to  the
foregoing,  interest  rates  are  evaluated on  the  basis  of  differentials or
anomalies that  may  exist between  different  countries. The  Series  may  hold
foreign  currency received in connection  with investments in foreign securities
and in  anticipation of  purchasing foreign  securities. (See  "Additional  Risk
Factors" below.)
 
    The  phrase "preservation of capital" when  applied to a domestic investment
company is generally understood to imply that the portfolio is invested in  very
low  risk securities and that the major risk is loss of purchasing power through
the effects of inflation or major changes in interest rates. However, while  the
World  Governments  Series  invests in  securities  which are  believed  to have
minimal credit risk, an error of judgment in selecting a currency or an interest
rate environment could result in a loss of capital.
 
    It is  contemplated  that  the  World  Governments  Series'  long-term  debt
investments  will  consist primarily  of securities  which  are believed  by the
Adviser to be of relatively high quality.  If after the Series purchases such  a
security,  the quality of the  security deteriorates significantly, the security
will be sold only if the Adviser believes it is advantageous to do so.
 
5.  INVESTMENT TECHNIQUES
 
    LENDING OF PORTFOLIO SECURITIES: Each of the Series may seek to increase its
income by  lending portfolio  securities. Such  loans will  usually be  made  to
member  firms (and  subsidiaries thereof)  of the  New York  Stock Exchange (the
"Exchange") and to  member banks  of the Federal  Reserve System,  and would  be
required  to  be  secured  continuously by  collateral  in  cash,  U.S. Treasury
securities or an irrevocable letter of  credit maintained on a current basis  at
an  amount at least equal  to the market value of  the securities loaned. If the
Adviser determines to make  securities loans, it is  intended that the value  of
the securities loaned would not exceed 10% of the value of the net assets of the
Series making the loans.
 
    EMERGING  MARKET  SECURITIES: Consistent  with their  respective objectives,
each Series may invest in securities  of issuers whose principal activities  are
located  in  emerging market  countries. Emerging  market countries  include any
country determined by  the Adviser to  have an emerging  market economy,  taking
into account a number of factors,
 
                                       12
<PAGE>
including  whether the country has a low- to middle- income economy according to
the International Bank for Reconstruction and Development, the country's foreign
currency debt rating, its political  and economic stability and the  development
of its financial and capital markets. The Adviser determines whether an issuer's
principal  activities are located  in an emerging  market country by considering
such factors as its  country of organization, the  principal trading market  for
its securities and the source of its revenues and assets. The issuer's principal
activities  generally are deemed to  be located in a  particular country if: (a)
the security is issued or guaranteed by the government of that country or any of
its agencies,  authorities or  instrumentalities; (b)  the issuer  is  organized
under  the laws of,  and maintains a  principal office in  that country; (c) the
issuer has its  principal securities  trading market  in that  country; (d)  the
issuer  derives 50% or  more of its  total revenues from  goods sold or services
performed in that country; or  (e) the issuer has 50%  or more of its assets  in
that country.
 
    BRADY  BONDS:  Each of  the  Series may  invest  in Brady  Bonds,  which are
securities created through  the exchange  of existing commercial  bank loans  to
public  and  private  entities in  certain  emerging  markets for  new  bonds in
connection with debt restructurings under  a debt restructuring plan  introduced
by  former U.S. Secretary of the Treasury, Nicholas F. Brady (the "Brady Plan").
Brady Plan  debt restructurings  have  been implemented  to date  in  Argentina,
Brazil,  Bulgaria,  Costa  Rica, Dominican  Republic,  Ecuador,  Jordan, Mexico,
Nigeria, Panama, the  Philippines, Poland,  Uruguay and  Venezuela. Brady  Bonds
have  been issued only recently, and for that  reason do not have a long payment
history. Brady Bonds may  be collateralized or  uncollateralized, are issued  in
various  currencies (but primarily  the U.S. dollar) and  are actively traded in
over-the-counter  secondary  markets.  U.S.  dollar-denominated,  collateralized
Brady Bonds, which may be fixed-rate bonds or floating-rate bonds, are generally
collateralized in full as to principal by U.S. Treasury zero coupon bonds having
the  same maturity as the bonds. Brady Bonds are often viewed as having three or
four valuation components:  the collateralized repayment  of principal at  final
maturity;  the collateralized  interest payments;  the uncollateralized interest
payments; and any  uncollateralized repayment  of principal  at maturity  (these
uncollateralized  amounts  constituting the  "residual risk").  In light  of the
residual risk of Brady  Bonds and the history  of defaults of countries  issuing
Brady  Bonds  with  respect  to  commercial bank  loans  by  public  and private
entities, investments in Brady Bonds may be viewed as speculative.
 
    REPURCHASE  AGREEMENTS:  Each  of  the  Series  may  enter  into  repurchase
agreements in order to earn income on available cash or as a temporary defensive
measure.  Under a repurchase agreement, a  Series acquires securities subject to
the seller's  agreement to  repurchase at  a specified  time and  price. If  the
seller  becomes subject to a proceeding under  the bankruptcy laws or its assets
are otherwise  subject to  a stay  order,  the Series'  right to  liquidate  the
securities  may be  restricted (during  which time  the value  of the securities
could decline).  As  discussed in  the  SAI,  each Series  has  adopted  certain
procedures intended to minimize risk.
 
    "WHEN-ISSUED"  SECURITIES: Each of the  Series (except the World Governments
Series) may purchase securities  on a "when-issued" or  on a "forward  delivery"
basis,  which means  that the securities  will be  delivered to the  Series at a
future date usually beyond customary settlement time. The commitment to purchase
a security for  which payment  will be made  on a  future date may  be deemed  a
separate  security. In general, a Series does  not pay for such securities until
received, and  does not  start  earning interest  on  the securities  until  the
contractual  settlement date. While awaiting delivery of securities purchased on
such bases, a Series will normally invest in liquid assets.
 
    MORTGAGE "DOLLAR ROLL" TRANSACTIONS:  Each of the  Total Return Series,  the
World Government Series and the Utilities Series may enter into mortgage "dollar
roll"  transactions with selected  banks and broker-dealers  pursuant to which a
Series sells mortgage-backed  securities for delivery  in the future  (generally
within 30 days) and simultaneously contracts to repurchase substantially similar
(same  type, coupon  and maturity)  securities on  a specified  future date. The
Series record these transactions as sale and purchase transactions, rather  than
as  borrowing  transactions. A  Series  will only  enter  into covered  rolls. A
"covered roll"  is  a  specific type  of  dollar  roll for  which  there  is  an
offsetting cash position or a cash equivalent security position which matures on
or  before the forward  settlement date of  the dollar roll  transaction. In the
event that the  party with whom  the Series contracts  to replace  substantially
similar securities on a future date fails to deliver such securities, the Series
may  not  be able  to  obtain such  securities at  the  price specified  in such
contract and  thus may  not  benefit from  the  price differential  between  the
current sales price and the repurchase price.
 
    RESTRICTED  SECURITIES: Each of the Series  may purchase securities that are
not registered under the  Securities Act of 1933  (the "1933 Act")  ("restricted
securities"),  including  those  that  can be  offered  and  sold  to "qualified
institutional  buyers"  under  Rule  144A   under  the  1933  Act  ("Rule   144A
securities").  A determination  is made  based upon  a continuing  review of the
trading markets for  a specific  Rule 144A  security, whether  such security  is
liquid and thus not subject to the
 
                                       13
<PAGE>
Series'  limitation on investing not more than 15% of its net assets in illiquid
investments. The Board of Trustees has  adopted guidelines and delegated to  MFS
the  daily function  of determining  and monitoring  the liquidity  of Rule 144A
securities. The Board, however, retains  oversight, focusing on factors such  as
valuation,  liquidity and  availability of  information. Investing  in Rule 144A
securities could  have the  effect of  decreasing the  level of  liquidity in  a
Series  to  the extent  that qualified  institutional buyers  become for  a time
uninterested in purchasing Rule 144A securities held in the Series' portfolio.
 
    CORPORATE ASSET-BACKED SECURITIES: Each of  the Emerging Growth Series,  the
Total   Return  Series  and  the  Utilities   Series  may  invest  in  corporate
asset-backed securities. These securities, issued by trusts and special  purpose
corporations, are backed by a pool of assets, such as credit card and automobile
loan receivables, representing the obligations of a number of different parties.
 
    Corporate  asset-backed securities  present certain risks.  For instance, in
the case of credit card receivables,  these securities may not have the  benefit
of  any security interest in the related collateral. Credit card receivables are
generally unsecured and the debtors are  entitled to the protection of a  number
of  state and federal consumer credit laws,  many of which give such debtors the
right to set off certain amounts owed on the credit cards, thereby reducing  the
balance  due. Most  issuers of  automobile receivables  permit the  servicers to
retain possession of the  underlying obligations. If the  servicer were to  sell
these  obligations to another  party, there is  a risk that  the purchaser would
acquire an interest superior  to that of the  holders of the related  automobile
receivables.  In addition, because of the large number of vehicles involved in a
typical issuance and technical  requirements under state  laws, the trustee  for
the  holders  of  the automobile  receivables  may  not have  a  proper security
interest in all of the obligations backing such receivables. Therefore, there is
the possibility  that recoveries  on  repossessed collateral  may not,  in  some
cases,  be available  to support  payments on  these securities.  The underlying
assets  (E.G.,  loans)  are  also  subject  to  prepayments  which  shorten  the
securities' weighted average life and may lower their return.
 
    Corporate  asset-backed  securities are  often backed  by  a pool  of assets
representing the obligations  of a number  of different parties.  To lessen  the
effect  of  failures by  obligors  on underlying  assets  to make  payments, the
securities  may  contain  elements  of  credit  support  which  fall  into   two
categories:  (i)  liquidity  protection;  and  (ii)  protection  against  losses
resulting from  ultimate  default  by  an  obligor  on  the  underlying  assets.
Liquidity  protection  refers to  the provision  of  advances, generally  by the
entity administering the pool of assets, to ensure that the receipt of  payments
on  the underlying  pool occurs in  a timely fashion.  Protection against losses
resulting from ultimate  default ensures payment  through insurance policies  or
letters of credit obtained by the issuer or sponsor from third parties. A Series
will  not pay any additional or separate  fees for credit support. The degree of
credit support  provided  for  each  issue  is  generally  based  on  historical
information  respecting the level of credit  risk associated with the underlying
assets. Delinquency or  loss in  excess of that  anticipated or  failure of  the
credit  support could  adversely affect  the return on  an investment  in such a
security.
 
    ZERO COUPON BONDS: Each  of the Total Return  Series, the World  Governments
Series  and the  Utilities Series  may invest  in zero  coupon bonds.  The Total
Return Series may  also invest in  deferred interest bonds  and PIK bonds.  Zero
coupon  and deferred  interest bonds  are debt  obligations which  are issued or
purchased at a significant discount  from face value. The discount  approximates
the  total amount of interest the bonds will accrue and compound over the period
until maturity  or  the  first interest  payment  date  at a  rate  of  interest
reflecting  the market rate of the security  at the time of issuance. While zero
coupon bonds do not require the periodic payment of interest, deferred  interest
bonds  provide for  a period  of delay  before the  regular payment  of interest
begins. PIK bonds are debt obligations which provide that the issuer may, at its
option, pay interest on  such bonds in  cash or in the  form of additional  debt
obligations. Such investments benefit the issuer by mitigating its need for cash
to  meet  debt service,  but also  require a  higher rate  of return  to attract
investors who are willing  to defer receipt of  such cash. Such investments  may
experience  greater volatility in market value  due to changes in interest rates
than debt obligations which make regular  payments of interest. The Series  will
accrue  income on such investments for tax and accounting purposes, as required,
which is distributable to shareholders and which, because no cash is received at
the time of accrual, may require  the liquidation of other portfolio  securities
to satisfy the Series' distribution obligations.
 
    COLLATERALIZED  MORTGAGE OBLIGATIONS AND MULTICLASS PASS-THROUGH SECURITIES:
Each of  the World  Governments Series  and the  Utilities Series  may invest  a
portion  of its assets  in collateralized mortgage  obligations or "CMOs," which
are debt obligations collateralized by  mortgage loans or mortgage  pass-through
securities.  Typically, CMOs are collateralized  by certificates issued by GNMA,
the Federal  National Mortgage  Association ("FNMA")  or the  Federal Home  Loan
 
                                       14
<PAGE>
Mortgage Corporation ("FHLMC"), but also may be collateralized by whole loans or
private  mortgage pass-through securities (such collateral collectively referred
to as "Mortgage Assets"). Each of these Series may also invest a portion of  its
assets  in multiclass  pass-through securities  which are  interests in  a trust
composed  of  Mortgage  Assets.  CMOs  (which  include  multiclass  pass-through
securities)  may be issued by agencies,  authorities or instrumentalities of the
U.S. Government or by private originators  of, or investors in, mortgage  loans,
including  savings  and  loan associations,  mortgage  banks,  commercial banks,
investment banks and special purpose subsidiaries of the foregoing. Payments  of
principal  of and interest  on the Mortgage Assets,  and any reinvestment income
thereon, provide the funds  to pay debt  service on the  CMOs or make  scheduled
distributions  on the multiclass pass-through securities.  In a CMO, a series of
bonds or  certificates are  usually issued  in multiple  classes with  different
maturities. Each class of CMOs, often referred to as a "tranche," is issued at a
specific  fixed  or floating  coupon rate  and  has a  stated maturity  or final
distribution date. Principal prepayments  on the Mortgage  Assets may cause  the
CMOs  to be retired substantially earlier  than their stated maturities or final
distribution dates, resulting in a loss of all or part of the premium if any has
been paid. Certain classes of CMOs have priority over others with respect to the
receipt of prepayments  on the mortgages.  Therefore, depending on  the type  of
CMOs  in which a Series  invests, the investment may be  subject to a greater or
lesser risk of prepayments than other types of mortgage-related securities.
 
    Each of  the World  Governments Series  and the  Utilities Series  may  also
invest  in parallel pay CMOs and  Planned Amortization Class CMOs ("PAC Bonds").
Parallel pay  CMOs are  structured to  provide payments  of principal  and  each
payment  date to more than one class.  PAC Bonds generally require payments of a
specified amount  of  principal on  each  payment  date. PAC  Bonds  are  always
parallel  pay CMOs with the required principal payment on such securities having
the highest priority after interest has been paid to all classes. For a  further
description  of CMOs, parallel pay  CMOs and PAC Bonds  and the risks related to
transactions therein, see the SAI.
 
    STRIPPED MORTGAGE-BACKED SECURITIES: The World Governments Series may invest
a portion of its assets  in stripped mortgage-backed securities ("SMBS"),  which
are  derivative  multiclass  mortgage  securities  usually  structured  with two
classes  that   receive  different   proportions  of   interest  and   principal
distributions  from  an  underlying  pool  of  mortgage  assets.  For  a further
description of SMBS and the risks related to transactions therein, see the SAI.
 
    LOAN PARTICIPATIONS  AND OTHER  DIRECT INDEBTEDNESS:  Each of  the  Emerging
Growth  Series and the Total Return Series may invest a portion of its assets in
"loan participations"  and  other  direct indebtedness.  By  purchasing  a  loan
participation,  a Series acquires some or all of the interest of a bank or other
lending institution  in a  loan to  a corporate  borrower. Many  such loans  are
secured,  and  most  impose  restrictive  covenants which  must  be  met  by the
borrower. These loans are  made generally to  finance internal growth,  mergers,
acquisitions,   stock  repurchases,  leveraged   buy-outs  and  other  corporate
activities. Such loans may be in default  at the time of purchase. A Series  may
also  purchase other direct  indebtedness such as trade  or other claims against
companies, which generally represent money owed by the company to a supplier  of
goods  and  services. These  claims may  also be  purchased at  a time  when the
company is  in default.  Certain of  the loan  participations and  other  direct
indebtedness  acquired by  a Series may  involve revolving  credit facilities or
other standby financing commitments  which obligate a  Series to pay  additional
cash on a certain date or on demand.
 
    The highly leveraged nature of many such loans and other direct indebtedness
may  make such  loans especially  vulnerable to  adverse changes  in economic or
market conditions. Loan participations and other direct indebtedness may not  be
in  the form of  securities or may  be subject to  restrictions on transfer, and
only limited opportunities may exist to resell such instruments. As a result,  a
Series  may be unable to sell such investments  at an opportune time or may have
to resell them at less than fair market value. For a further discussion of  loan
participations,  other direct indebtedness and the risks related to transactions
therein, see the SAI.
 
    MORTGAGE PASS-THROUGH SECURITIES: Each  of the Total  Return Series and  the
World  Governments  Series  may  invest  in  mortgage  pass-through  securities.
Mortgage  pass-through  securities  are  securities  representing  interests  in
"pools"  of  mortgage  loans.  The  Utilities  Series  may  invest  in  mortgage
pass-through securities that are securities issued or guaranteed as to principal
and  interest   by   the  U.S.   Government,   its  agencies,   authorities   or
instrumentalities.  Monthly payments of interest and principal by the individual
borrowers on mortgages are passed through to the holders of the securities  (net
of  fees paid to the issuer or guarantor  of the securities) as the mortgages in
the underlying mortgage pools are paid off. Payment of principal and interest on
some  mortgage  pass-through  securities  (but  not  the  market  value  of  the
 
                                       15
<PAGE>
securities  themselves) may be  guaranteed by the  full faith and  credit of the
U.S. Government (in the case of securities guaranteed by GNMA); or guaranteed by
U.S. Government-sponsored  corporations  (such  as  FNMA  or  FHLMC,  which  are
supported only by the discretionary authority of the U.S. Government to purchase
the  agency's obligations). Mortgage pass-through  securities may also be issued
by  non-governmental  issuers  (such  as  commercial  banks,  savings  and  loan
institutions,  private mortgage insurance companies,  mortgage bankers and other
secondary market  issuers).  See the  SAI  for  a further  discussion  of  these
securities.
 
    INDEXED  SECURITIES: Each of  the Total Return  Series, the Utilities Series
and the World Governments Series may invest in indexed securities whose value is
linked to  foreign currencies,  interest rates,  commodities, indices  or  other
financial  indicators. Most  indexed securities  are short  to intermediate term
fixed income securities whose values at maturity (I.E., principal value)  and/or
interest  rates rise or  fall according to  the change in  one or more specified
underlying instruments.  Indexed  securities  may be  positively  or  negatively
indexed  (I.E., their principal value or interest rates may increase or decrease
if the underlying instrument appreciates),  and may have return  characteristics
similar  to direct investments  in the underlying  instrument or to  one or more
options on the underlying  instrument. Indexed securities  may be more  volatile
than the underlying instrument itself.
 
    SWAPS  AND  RELATED TRANSACTIONS:  As one  way of  managing its  exposure to
different types  of investments,  the World  Governments Series  may enter  into
interest   rate  swaps,  currency  swaps  and  other  types  of  available  swap
agreements, such as caps,  collars and floors. Swaps  involve the exchange by  a
Series  with another party  of cash payments based  upon different interest rate
indexes, currencies, and other  prices or rates, such  as the value of  mortgage
prepayment rates. For example, in the typical interest rate swap, a Series might
exchange  a sequence of  cash payments based  on a floating  rate index for cash
payments based  on  a fixed  rate.  Payments made  by  both parties  to  a  swap
transaction are based on a principal amount determined by the parties.
 
    The  World Governments  Series may also  purchase and sell  caps, floors and
collars. In a typical cap or floor agreement, one party agrees to make  payments
only  under specified circumstances, usually  in return for payment  of a fee by
the counterparty. For example, the purchase of an interest rate cap entitles the
buyer, to the  extent that a  specified index exceeds  a predetermined  interest
rate,  to receive payments of interest on a contractually-based principal amount
from the counterparty selling  such interest rate cap.  The sale of an  interest
rate  floor obligates the seller to make payments to the extent that a specified
interest rate falls below  an agreed-upon level.  A collar arrangement  combines
elements of buying a cap and selling a floor.
 
    Swap  agreements will tend  to shift a Series'  investment exposure from one
type of  investment to  another. For  example, if  a Series  agreed to  exchange
payments  in dollars for payments  in foreign currency, in  each case based on a
fixed rate, the swap agreement would tend to decrease a Series' exposure to U.S.
interest rates and increase its exposure to foreign currency and interest rates.
Caps and floors have an effect  similar to buying or writing options.  Depending
on  how they  are used,  swap agreements  may increase  or decrease  the overall
volatility of a Series' investments and its share price and yield.
 
    Swap agreements are sophisticated hedging instruments that typically involve
a small investment  of cash relative  to the  magnitude of risks  assumed. As  a
result,  swaps can be  highly volatile and  may have a  considerable impact on a
Series' performance.  Swap  agreements  are  subject to  risks  related  to  the
counterparty's   ability  to   perform,  and  may   decline  in   value  if  the
counterparty's creditworthiness deteriorates. A Series may also suffer losses if
it is unable  to terminate outstanding  swap agreements or  reduce its  exposure
through offsetting transactions.
 
    Swaps,  caps,  floors and  collars are  highly specialized  activities which
involve certain risks.  See the SAI  for further information  on, and the  risks
involved in, these activities.
 
    OPTIONS  ON SECURITIES: Each of the Emerging Growth Series, the Total Return
Series and the World  Governments Series may write  (sell) covered put and  call
options  and purchase put and  call options on securities.  Each of these Series
will write options on securities for the purpose of increasing its return and/or
to protect the value of its portfolio.  In particular, where a Series writes  an
option  that expires unexercised or is closed out  by the Series at a profit, it
will retain the premium paid for the option which will increase its gross income
and will offset in part the  reduced value of the portfolio security  underlying
the  option, or the  increased cost of  portfolio securities to  be acquired. In
contrast, however, if the  price of the underlying  security moves adversely  to
the  Series'  position, the  option  may be  exercised  and the  Series  will be
 
                                       16
<PAGE>
required to purchase or sell the underlying security at a disadvantageous price,
which may only be partially offset by the amount of the premium. The Series  may
also  write combinations of put and call  options on the same security, known as
"straddles." Such transactions can generate  additional premium income but  also
present increased risk.
 
    By  writing a call option on a  security, a Series limits its opportunity to
profit from any increase in the  market value of the underlying security,  since
the  holder will usually exercise  the call option when  the market value of the
underlying security exceeds the exercise price of the call. However, the  Series
retains  the risk of depreciation in value of securities on which it has written
call options.
 
    Each of these Series may also  purchase put or call options in  anticipation
of  market fluctuations which may adversely affect the value of its portfolio or
the prices of securities that a Series wants to purchase at a later date. In the
event that the  expected market fluctuations  occur, the Series  may be able  to
offset  the resulting  adverse effect  on its  portfolio, in  whole or  in part,
through the options purchased. The  premium paid for a  put or call option  plus
any  transaction costs will reduce  the benefit, if any,  realized by the Series
upon exercise  or  liquidation of  the  option, and,  unless  the price  of  the
underlying security changes sufficiently, the option may expire without value to
the Series.
 
    In  certain instances, the Emerging Growth  Series may enter into options on
Treasury securities that  are "reset"  options or  "adjustable strike"  options.
These  options provide for periodic adjustment of  the strike price and may also
provide for  the periodic  adjustment of  the  premium during  the term  of  the
option. The SAI contains a further discussion of these investments.
 
    OPTIONS  ON STOCK  INDICES: Each  of the  Emerging Growth  Series, the Total
Return Series and  the Utilities Series  may write (sell)  covered call and  put
options and purchase call and put options on stock indices. Each of these Series
may  write options  on stock  indices for  the purpose  of increasing  its gross
income and to protect its portfolio against declines in the value of  securities
it  owns or increases in  the value of securities to  be acquired. When a Series
writes an option on a stock index, and the value of the index moves adversely to
the holder's position,  the option will  not be exercised,  and the Series  will
either  close out the  option at a profit  or allow it  to expire unexercised. A
Series will thereby retain the amount  of the premium, less related  transaction
costs, which will increase its gross income and offset part of the reduced value
of portfolio securities or the increased cost of securities to be acquired. Such
transactions, however, will constitute only partial hedges against adverse price
fluctuations,  since any such fluctuations will be  offset only to the extent of
the premium received by  a Series for  the writing of  the option, less  related
transaction  costs.  In addition,  if  the value  of  an underlying  index moves
adversely to a  Series' option position,  the option may  be exercised, and  the
Series  will experience a loss which may  only be partially offset by the amount
of the premium received.
 
    Each of these Series may also purchase put or call options on stock  indices
in  order, respectively, to hedge its investments  against a decline in value or
to attempt to reduce the risk of missing a market or industry segment advance. A
Series' possible loss in either case will be limited to the premium paid for the
option, plus related transaction costs.
 
    "YIELD CURVE"  OPTIONS:  Each of  the  Total  Return Series  and  the  World
Governments  Series  may enter  into  options on  the  yield "spread,"  or yield
differential, between  two securities,  a transaction  referred to  as a  "yield
curve"  option,  for  hedging and  non-hedging  (an effort  to  increase current
income) purposes. In contrast to other types of options, a yield curve option is
based on the difference between the yields of designated securities rather  than
the  actual prices  of the  individual securities,  and is  settled through cash
payments. Accordingly, a yield curve option is profitable to the holder if  this
differential  widens (in the case of a call)  or narrows (in the case of a put),
regardless of  whether  the yields  of  the underlying  securities  increase  or
decrease.  Yield curve options written by a  Series will be covered as described
in the SAI.  The trading  of yield  curve options is  subject to  all the  risks
associated  with  trading  other  types of  options,  as  discussed  below under
"Additional Risk Factors"  and in  the SAI.  In addition,  such options  present
risks  of loss  even if the  yield on  one of the  underlying securities remains
constant, if the  spread moves  in a  direction or to  an extent  which was  not
anticipated.
 
    FUTURES CONTRACTS AND OPTIONS ON FUTURES CONTRACTS: Each of the Total Return
Series,  the World Governments Series and  the Utilities Series may purchase and
sell futures contracts on foreign or domestic fixed income securities or indices
of such securities, including  municipal bond indices and  any other indices  of
foreign  or  domestic  fixed income  securities  that may  become  available for
trading ("Futures Contracts"). Each of these Series may also purchase and  write
options  on such Futures Contracts ("Options on Futures Contracts"). Each of the
Emerging Growth Series and the Total Return Series may purchase and sell Futures
Contracts on  stock  indices,  while  the  Emerging  Growth  Series,  the  Total
 
                                       17
<PAGE>
Return  Series,  the  World  Governments Series  and  the  Utilities  Series may
purchase and sell Futures Contracts on foreign currencies or indices of  foreign
currencies.  Each of these  Series may also  purchase and write  Options on such
Futures Contracts.
 
    Such  transactions  will  be  entered  into  for  hedging  purposes  or  for
non-hedging purposes to the extent permitted by applicable law. Each Series will
incur  brokerage fees when it purchases and sells Futures Contracts, and will be
required to  maintain margin  deposits. In  addition, Futures  Contracts  entail
risks.  Although the Adviser believes that use  of such Contracts will benefit a
Series, if its investment judgment about the general direction of exchange rates
or the stock market is incorrect, the Series' overall performance may be  poorer
than  if it had not entered into any  such contract and the Series may realize a
loss. A  Series  will  not  enter  into  any  Futures  Contract  if  immediately
thereafter  the value  of securities and  other obligations  underlying all such
Futures Contracts held by such Series would exceed 50% of the value of its total
assets.
 
    Purchases of Options on Futures Contracts may present less risk in hedging a
Series' portfolio than the purchase or sale of the underlying Futures  Contracts
since  the potential loss is  limited to the amount  of the premium plus related
transaction costs,  although it  may  be necessary  to  exercise the  option  to
realize  any profit, which  results in the establishment  of a futures position.
The writing of Options on Futures Contracts, however, does not present less risk
than the trading of Futures Contracts and will constitute only a partial  hedge,
up  to  the  amount  of the  premium  received.  In addition,  if  an  option is
exercised, a Series may suffer a loss on the transaction.
 
    Futures Contracts and Options on Futures Contracts that are entered into  by
a Series will be traded on U.S. and foreign exchanges.
 
    FORWARD  CONTRACTS:  Each  of  the Series  may  enter  into  forward foreign
currency exchange contracts for the  purchase or sale of  a fixed quantity of  a
foreign  currency at a  future date ("Forward Contracts").  Each of these Series
may enter  into  Forward Contracts  for  hedging purposes  and  for  non-hedging
purposes  (I.E., speculative purposes). By entering into transactions in Forward
Contracts for hedging purposes, a Series may be required to forego the  benefits
of  advantageous changes in exchange rates and, in the case of Forward Contracts
entered into for non-hedging  purposes, a Series may  sustain losses which  will
reduce  its  gross income.  Such  transactions, therefore,  could  be considered
speculative. Forward Contracts are traded over-the-counter and not on  organized
commodities or securities exchanges. As a result, Forward Contracts operate in a
manner distinct from exchange-traded instruments, and their use involves certain
risks  beyond those associated with transactions in Futures Contracts or options
traded on exchanges. A Series may choose to, or be required to, receive delivery
of the  foreign currencies  underlying Forward  Contracts it  has entered  into.
Under  certain  circumstances,  such  as where  the  Adviser  believes  that the
applicable exchange rate is unfavorable at the time the currencies are  received
or  the Adviser anticipates, for  any other reason, that  the exchange rate will
improve, the Series may hold such currencies for an indefinite period of time. A
Series may also enter into a Forward  Contract on one currency to hedge  against
risk  of  loss arising  from  fluctuations in  the  value of  a  second currency
(referred to  as  a  "cross hedge")  if,  in  the judgment  of  the  Adviser,  a
reasonable degree of correlation can be expected between movements in the values
of  the  two  currencies.  Each  of  these  Series  has  established  procedures
consistent with statements of the SEC and its staff regarding the use of Forward
Contracts by registered investment companies,  which requires use of  segregated
assets or "cover" in connection with the purchase and sale of such contracts.
 
    OPTIONS  ON FOREIGN  CURRENCIES: Each of  the Series may  purchase and write
options on foreign currencies ("Options on Foreign Currencies") for the  purpose
of  protecting against declines in the  dollar value of portfolio securities and
against increases in the  dollar cost of  securities to be  acquired. As in  the
case  of other types  of options, however,  the writing of  an Option on Foreign
Currency will constitute only a partial hedge,  up to the amount of the  premium
received, and a Series may be required to purchase or sell foreign currencies at
disadvantageous  exchange rates,  thereby incurring  losses. The  purchase of an
Option  on  Foreign   Currency  may  constitute   an  effective  hedge   against
fluctuations  in exchange rates although, in the event of rate movements adverse
to a Series' position, it may forfeit the entire amount of the premium paid  for
the  option plus related transaction  costs. A Series may  also choose to, or be
required to, receive delivery  of the foreign  currencies underlying Options  on
Foreign  Currencies it  has entered into.  Under certain  circumstances, such as
where the Adviser believes that the  applicable exchange rate is unfavorable  at
the  time the currencies are received or  the Adviser anticipates, for any other
reason, that the exchange rate will  improve, a Series may hold such  currencies
for an indefinite period of time.
 
                                       18
<PAGE>
6.  ADDITIONAL RISK FACTORS
 
    OPTIONS,  FUTURES CONTRACTS  AND FORWARD CONTRACTS:  Although certain Series
will enter into transactions in  options, Futures Contracts, Options on  Futures
Contracts,  Forward  Contracts and  Options  on Foreign  Currencies  for hedging
purposes, such transactions nevertheless involve  certain risks. For example,  a
lack  of  correlation between  the instrument  underlying  an option  or Futures
Contract and the  assets being  hedged, or unexpected  adverse price  movements,
could render a Series' hedging strategy unsuccessful and could result in losses.
Certain  Series also may enter into  transactions in options, Futures Contracts,
Options on  Futures  Contracts and  Forward  Contracts for  other  than  hedging
purposes,  which  involves greater  risk. In  particular, such  transactions may
result in losses for a Series which  are not offset by gains on other  portfolio
positions,  thereby reducing gross income. In addition, foreign currency markets
may be extremely volatile from time to time. There also can be no assurance that
a liquid secondary market will exist for  any contract purchased or sold, and  a
Series  may be  required to  maintain a  position until  exercise or expiration,
which could result in losses. The SAI  contains a description of the nature  and
trading  mechanics of options, Futures  Contracts, Options on Futures Contracts,
Forward Contracts and Options on  Foreign Currencies, and includes a  discussion
of the risks related to transactions therein.
 
    Transactions   in  Forward  Contracts  may  be  entered  into  only  in  the
over-the-counter market. Futures Contracts and Options on Futures Contracts  may
be  entered into  on U.S. exchanges  regulated by the  Commodity Futures Trading
Commission and on  foreign exchanges.  In addition, the  securities and  indexes
underlying options, Futures Contracts and Options on Futures Contracts traded by
the Series will include both domestic and foreign securities.
 
    LOWER  RATED BONDS:  Each of  the Emerging  Growth Series,  the Total Return
Series and the Utilities Series may invest in fixed income securities rated  Baa
by  Moody's or  BBB by  S&P or  Fitch and  comparable unrated  securities. These
securities, while  normally  exhibiting  adequate  protection  parameters,  have
speculative   characteristics  and  changes  in  economic  conditions  or  other
circumstances are more likely to lead  to a weakened capacity to make  principal
and interest payments than in the case of higher grade securities.
 
    Each  of these  Series may also  invest in  securities rated Ba  or lower by
Moody's or  BB  or lower  by  S&P or  Fitch  and comparable  unrated  securities
(commonly  known as "junk bonds") to the  extent described above. See Appendix A
to this Prospectus  for a  description of  these ratings.  These securities  are
considered  speculative  and,  while  generally  providing  greater  income than
investments in higher rated securities,  will involve greater risk of  principal
and income (including the possibility of default or bankruptcy of the issuers of
such  securities) and may involve greater volatility of price (especially during
periods of economic uncertainty or change) than securities in the higher  rating
categories.  However, since yields  vary over time, no  specific level of income
can ever be  assured. These lower  rated high yielding  fixed income  securities
generally tend to reflect economic changes and short-term corporate and industry
developments  to  a  greater extent  than  higher rated  securities  which react
primarily to fluctuations in the general level of interest rates (although these
lower rated fixed  income securities are  also affected by  changes in  interest
rates,  the market's  perception of  their credit  quality, and  the outlook for
economic growth). In  the past, economic  downturns or an  increase in  interest
rates have, under certain circumstances, caused a higher incidence of default by
the  issuers of these securities and may do  so in the future, especially in the
case of highly leveraged issuers. During certain periods, the higher yields on a
Series' lower rated  high yielding  fixed income securities  are paid  primarily
because of the increased risk of loss of principal and income, arising from such
factors as the heightened possibility of default or bankruptcy of the issuers of
such  securities. Due to the fixed income payments of these securities, a Series
may continue to earn the same level of interest income while its net asset value
declines due  to portfolio  losses, which  could result  in an  increase in  the
Series'  yield despite the actual loss of  principal. The market for these lower
rated fixed income securities may be less liquid than the market for  investment
grade  fixed income securities, and judgment may at times play a greater role in
valuing these  securities than  in the  case of  investment grade  fixed  income
securities.  Changes in the value of  securities subsequent to their acquisition
will not  affect cash  income or  yield  to maturity  to a  Series but  will  be
reflected  in the net asset value of shares  of the Series. See the SAI for more
information on lower rated securities.
 
    FOREIGN SECURITIES: Each of the Series may invest in dollar-denominated  and
non-dollar-denominated  foreign  debt  securities.  Investing  in  securities of
foreign  issuers  generally  involves  risks  not  ordinarily  associated   with
investing  in securities of domestic issuers.  These include changes in currency
rates, exchange control regulations, governmental administration or economic  or
monetary  policy (in  the U.S. or  abroad) or circumstances  in dealings between
nations. Costs may be  incurred in connection  with conversions between  various
currencies.  Special considerations  may also  include more  limited information
about foreign issuers,  higher brokerage costs,  different accounting  standards
and thinner
 
                                       19
<PAGE>
trading  markets.  Foreign  securities markets  may  also be  less  liquid, more
volatile and less subject to government  supervision than in the United  States.
Investments  in foreign countries  could be affected  by other factors including
expropriation, confiscatory  taxation and  potential difficulties  in  enforcing
contractual  obligations and  could be  subject to  extended settlement periods.
Each of  the  Series may  hold  foreign  currency received  in  connection  with
investments in foreign securities when, in the judgment of the Adviser, it would
be  beneficial to convert such currency into U.S. dollars at a later date, based
on anticipated changes in the relevant exchange rate. Such Series may also  hold
foreign  currency in anticipation of purchasing  foreign securities. See the SAI
for further  discussion  of  foreign  securities  and  the  holding  of  foreign
currency, as well as the associated risks.
 
    AMERICAN  DEPOSITARY RECEIPTS: Each  of the Series may  invest in ADRs which
are certificates issued by  a U.S. depository (usually  a bank) and represent  a
specified  quantity of shares of an underlying  non-U.S. stock on deposit with a
custodian bank as collateral. Because  ADRs trade on U.S. securities  exchanges,
the Adviser does not treat them as foreign securities. However, they are subject
to many of the risks of foreign securities such as changes in exchange rates and
more limited information about foreign issuers.
 
    EMERGING  MARKET  SECURITIES:  Each of  the  Series may  invest  in emerging
markets. In addition to  the general risks of  investing in foreign  securities,
investments  in  emerging  markets  involve special  risks.  Securities  of many
issuers in emerging markets may be less liquid and more volatile than securities
of comparable domestic issuers. These  securities may be considered  speculative
and,  while  generally  offering higher  income  and the  potential  for capital
appreciation, may present significantly greater risk. Emerging markets may  have
different clearance and settlement procedures, and in certain markets there have
been  times when settlements  have been unable  to keep pace  with the volume of
securities transactions,  making  it  difficult to  conduct  such  transactions.
Delays  in settlement could  result in temporary  periods when a  portion of the
assets of a Series is uninvested and no return is earned thereon. The  inability
of a Series to make intended security purchases due to settlement problems could
cause a Series to miss attractive investment opportunities. Inability to dispose
of  portfolio securities due to settlement problems  could result in losses to a
Series due  to subsequent  declines  in value  of  the portfolio  securities,  a
decrease  in the level of  liquidity in a Series' portfolio,  or if a Series has
entered into  a  contract  to  sell the  security,  possible  liability  to  the
purchaser.  Certain markets may require  payment for securities before delivery,
and in such  markets a Series  bears the risk  that the securities  will not  be
delivered  and that the Series' payments will not be returned. Securities prices
in emerging  markets  can  be  significantly more  volatile  than  in  the  more
developed  nations  of  the  world,  reflecting  the  greater  uncertainties  of
investing in less  established markets and  economies. In particular,  countries
with emerging markets may have relatively unstable governments, present the risk
of   nationalization  of  businesses,  restrictions  on  foreign  ownership,  or
prohibitions of repatriation of assets, and may have less protection of property
rights than more developed countries.  The economies of countries with  emerging
markets  may be  predominantly based  on only  a few  industries, may  be highly
vulnerable to changes in local or  global trade conditions, and may suffer  from
extreme  and volatile debt burdens or  inflation rates. Local securities markets
may trade a small number of securities and may be unable to respond  effectively
to  increases  in  trading  volume,  potentially  making  prompt  liquidation of
substantial holdings difficult  or impossible  at times.  Securities of  issuers
located  in countries with  emerging markets may  have limited marketability and
may be subject to more abrupt or erratic movements.
 
    Certain  emerging  markets  may   require  governmental  approval  for   the
repatriation  of  investment  income,  capital  or  the  proceeds  of  sales  of
securities by foreign investors.  In addition, if a  deterioration occurs in  an
emerging  market's balance  of payments  or for  other reasons,  a country could
impose temporary restrictions on foreign capital remittances. A Series could  be
adversely   affected  by  delays  in,  or  a  refusal  to  grant,  any  required
governmental approval for repatriation of capital, as well as by the application
to the Series of any restrictions on investments.
 
    Investment in  certain  foreign  emerging market  debt  obligations  may  be
restricted  or controlled to varying degrees. These restrictions or controls may
at times preclude investment in certain foreign emerging market debt obligations
and increase the expenses of a Series.
 
    NON-DIVERSIFICATION: Each of the World Governments Series and the  Utilities
Series  is "non-diversified," as that term  is defined in the Investment Company
Act of 1940 (the "1940 Act"), but intends to qualify as a "regulated  investment
company"  ("RIC") for federal income tax  purposes. This means, in general, that
although more  than 5%  of  the Series'  total assets  may  be invested  in  the
securities  of one issuer (including a foreign government), at the close of each
quarter of its taxable year the aggregate amount of such holdings may not exceed
50% of the value of its total assets, and  no more than 25% of the value of  its
total assets may be invested in the securities of a single issuer. To the extent
that  a non-diversified  Series at  times may hold  the securities  of a smaller
number  of   issuers   than   if   it  were   "diversified"   (as   defined   in
 
                                       20
<PAGE>
the  1940 Act), the  Series will at such  times be subject  to greater risk with
respect to its portfolio securities than a fund that invests in a broader  range
of  securities, because changes in the  financial condition or market assessment
of a single issuer  may cause greater fluctuations  in the Series' total  return
and the net asset value of its shares.
                              -------------------
 
SHORT-TERM  INVESTMENTS FOR  TEMPORARY DEFENSIVE  PURPOSES --  During periods of
unusual market conditions when the Adviser believes that investing for temporary
defensive purposes is appropriate,  or in order  to meet anticipated  redemption
requests, a large portion or all of the assets of each Series may be invested in
cash (including foreign currency) or cash equivalents including, but not limited
to,   obligations  of   banks  (including  certificates   of  deposit,  bankers'
acceptances,  time  deposits  and  repurchase  agreements),  commercial   paper,
short-term notes, U.S. Government Securities and related repurchase agreements.
 
PORTFOLIO TRADING
 
    Each   Series  intends  to  manage  its  portfolio  by  buying  and  selling
securities, as  well as  holding  securities to  maturity,  to help  attain  its
investment objectives and policies.
 
    Each  Series will engage in portfolio  trading if it believes a transaction,
net  of  costs  (including  custodian  charges),  will  help  in  attaining  its
investment  objectives. In trading portfolio securities,  a Series seeks to take
advantage of  market  developments,  yield disparities  and  variations  in  the
creditworthiness  of issuers. For  a description of the  strategies which may be
used by the Series in trading portfolio securities, see "Portfolio  Transactions
and  Brokerage Commissions" in the SAI.  The Total Return Series' portfolio will
be managed actively with respect to the Series' fixed income securities and  the
asset  allocations modified as the Adviser  deems necessary. Although the Series
does not  intend to  seek short-term  profits, fixed  income securities  in  its
portfolio  will be sold whenever the Adviser believes it is appropriate to do so
without regard to the length of time  the particular assets may have been  held.
With  respect to its equity securities, the  Total Return Series does not intend
to trade in  securities for  short-term profits and  anticipates that  portfolio
securities  ordinarily will be held for one  year or longer. However, the Series
will effect trades whenever it believes that changes in its portfolio securities
are appropriate.
 
    Because each of  the Utilities Series  and the World  Governments Series  is
expected  to  have a  portfolio turnover  rate of  over 100%,  transaction costs
incurred by the Series and the realized  capital gains and losses of the  Series
may be greater than that of a fund with a lesser portfolio turnover rate.
 
    The  primary consideration  in placing portfolio  security transactions with
broker-dealers for execution  is to  obtain, and maintain  the availability  of,
execution  at  the  most  favorable  prices and  in  the  most  effective manner
possible. Consistent with the foregoing primary consideration, the Rules of Fair
Practice of the National  Association of Securities  Dealers, Inc. (the  "NASD")
and  such other policies as the Trustees of the Trust may determine, the Adviser
may consider sales  of Contracts for  which the Trust  is an investment  option,
together  with sales of shares  of other investment company  clients of MFS Fund
Distributors, Inc., the distributor of shares of the Trust and of the MFS Family
of Funds, as a factor in the selection of broker-dealers to execute each Series'
portfolio transactions.  From  time  to  time the  Adviser  may  direct  certain
portfolio transactions to broker-dealer firms which, in turn, have agreed to pay
a portion of the Series' operating expenses (e.g., fees charged by the custodian
of  the Series' assets). For a further  discussion of portfolio trading, see the
SAI.
                              -------------------
 
    The SAI includes a  discussion of other investment  policies and listing  of
specific  investment restrictions which  govern the investment  policies of each
Series. The specific investment  restrictions listed in the  SAI may be  changed
without  shareholder  approval unless  indicated  otherwise (see  the  SAI). The
Series' investment limitations, policies and rating standards are adhered to  at
the  time  of  purchase  or  utilization  of  assets;  a  subsequent  change  in
circumstances will not be considered to result in a violation of policy.
 
7.  MANAGEMENT OF THE SERIES
 
    The  Trust's  Board  of  Trustees,   as  part  of  its  overall   management
responsibility,  oversees  various  organizations responsible  for  each Series'
day-to-day management.
 
INVESTMENT ADVISER -- MFS manages each Series pursuant to an Investment Advisory
Agreement with the  Trust on behalf  of each  Series dated April  14, 1994  (the
"Advisory  Agreement"). Under  the Advisory  Agreement, MFS  provides the Series
 
                                       21
<PAGE>
with overall  investment advisory  services.  Subject to  such policies  as  the
Trustees  may determine, MFS makes investment decisions for each Series. For its
services and  facilities,  MFS receives  a  management fee,  computed  and  paid
monthly,  in an amount equal to the  following annual rates of the average daily
net assets of each Series:
 
<TABLE>
<CAPTION>
                                                                                              PERCENTAGE OF THE
                                                                                              AVERAGE DAILY NET
                                                                                                    ASSETS
SERIES                                                                                          OF EACH SERIES
- ------------------------------------------------------------------------------------------  ----------------------
<S>                                                                                         <C>
Emerging Growth Series....................................................................             0.75%
Total Return Series.......................................................................             0.75%
Utilities Series..........................................................................             0.75%
World Governments Series..................................................................             0.75%
</TABLE>
 
    For the fiscal  year ended  December 31,  1996, MFS  received the  following
management  fees from  the Series under  the Advisory Agreement  and assumed the
following amounts of the Series' expenses (see "Expenses" below);
 
<TABLE>
<CAPTION>
                                                                                 MANAGEMENT FEE  EXPENSES ASSUMED
SERIES                                                                            PAID TO MFS         BY MFS
- -------------------------------------------------------------------------------  --------------  ----------------
<S>                                                                              <C>             <C>
Emerging Growth Series.........................................................    $  314,262       $   62,962
Total Return Series............................................................        60,979           87,721
Utilities Series...............................................................        39,863           91,877
World Governments Series.......................................................       126,898          172,556
</TABLE>
 
    MFS or its affiliates will pay  a fee to Connecticut General Life  Insurance
Company  ("CIGNA") equal,  on an  annualized basis,  0.15% of  the aggregate net
assets of the Trust up to $200 million and 0.20% of the aggregate net assets  of
the  Trust  over $200  million, attributable  to  Contracts offered  by separate
accounts of CIGNA or their affiliates. Such fees will not be paid by the Series,
their shareholders, or by the Contract holders.
 
    The identity and background of the portfolio managers for each Series is set
forth below. Unless  indicated otherwise,  each portfolio manager  has acted  in
that capacity since the commencement of investment operations of each Series.
 
<TABLE>
<CAPTION>
SERIES                                                         PORTFOLIO MANAGERS
- -----------------------------  -----------------------------------------------------------------------------------
<S>                            <C>
Emerging Growth Series         John W. Ballen, a Senior Vice President of MFS, has been employed by the Adviser as
                               a  portfolio manager since 1984. Toni Y. Shimura, a Vice President of MFS, has been
                               employed by the Adviser  as a portfolio  manager since 1987.  Ms. Shimura became  a
                               portfolio manager of the Series on November 30, 1995.
Total Return Series            David  M. Calabro, a Vice President  of MFS, has been employed  by the Adviser as a
                               portfolio manager since 1992. Mr. Calabro is the head of this portfolio  management
                               team  and a manager of the common  stock portion of the Series' portfolio. Geoffrey
                               L. Kurinsky, a Senior Vice President of MFS, has been employed by the Adviser as  a
                               portfolio  manager since  1987. Mr.  Kurinsky is the  manager of  the Series' fixed
                               income securities. Judith N. Lamb,  a Vice President of  MFS, has been employed  by
                               the Adviser as a portfolio manager since 1992. Ms. Lamb is a manager of the Series'
                               convertible  securities. Lisa B. Nurme, a Vice  President of MFS, has been employed
                               by the Adviser as  a portfolio manager since  1987. Ms. Nurme is  a manager of  the
                               common  stock  portion  of the  Series'  portfolio.  Maura A.  Shaughnessy,  a Vice
                               President of MFS, has  been employed by  the Adviser as  a portfolio manager  since
                               1991.  Ms. Shaughnessy  is a  manager of  the common  stock portion  of the Series'
                               portfolio. Each individual  became a portfolio  manager of the  Series on July  19,
                               1995.
Utilities Series               Maura  A. Shaughnessy, a  Vice President of  the Adviser, has  been employed by the
                               Adviser as a portfolio manager since 1991.
World Governments Series       Stephen C. Bryant, a Senior Vice President of the Adviser, has been employed by the
                               Adviser as a portfolio manager since 1987.
</TABLE>
 
    MFS also serves as investment adviser to each of the other funds in the  MFS
Family  of Funds  (the "MFS Funds")  and to  MFS-Registered Trademark- Municipal
Income Trust, MFS Multimarket Income Trust, MFS Government Markets Income Trust,
MFS Intermediate  Income Trust,  MFS  Charter Income  Trust, MFS  Special  Value
Trust,  MFS Institutional Trust,  MFS Union Standard  Trust, MFS/Sun Life Series
Trust, and seven  variable accounts, each  of which is  a registered  investment
 
                                       22
<PAGE>
company established by Sun Life Assurance Company of Canada (U.S.) ("Sun Life of
Canada  (U.S.)") in connection  with the sale  of various fixed/variable annuity
contracts. MFS  and its  wholly owned  subsidiary, MFS  Institutional  Advisers,
Inc., provide investment advice to substantial private clients.
 
    MFS  is America's oldest  mutual fund organization.  MFS and its predecessor
organizations have  a history  of  money management  dating  from 1924  and  the
founding  of the first mutual fund in the United States, Massachusetts Investors
Trust.  Net  assets  under   the  management  of   the  MFS  organization   were
approximately  $52.8  billion on  behalf of  approximately 2.3  million investor
accounts as of February 28, 1997. As of such date, the MFS organization  managed
approximately  $28.9  billion  of  assets  invested  in  equity  securities  and
approximately $19.9  billion  of assets  invested  in fixed  income  securities.
Approximately  $4.0  billion  of  the  assets managed  by  MFS  are  invested in
securities of foreign issuers and non-U.S. dollar-denominated securities of U.S.
issuers. MFS is a subsidiary  of Sun Life of Canada  (U.S.), which in turn is  a
wholly  owned subsidiary of  Sun Life Assurance Company  of Canada ("Sun Life").
The Directors of MFS are A. Keith  Brodkin, Jeffrey L. Shames, Arnold D.  Scott,
John D. McNeil and Donald A. Stewart. Mr. Brodkin is the Chairman, Mr. Shames is
the  President  and Mr.  Scott  is the  Secretary  and a  Senior  Executive Vice
President of MFS.  Messrs. McNeil and  Stewart are the  Chairman and  President,
respectively,  of Sun Life. Sun Life, a mutual life insurance company, is one of
the largest international life insurance companies and has been operating in the
United States since 1895, establishing a  headquarters office here in 1973.  The
executive officers of MFS report to the Chairman of Sun Life.
 
    A.  Keith Brodkin, the Chairman  and a Director of  MFS, is the Chairman and
President and a Trustee of the Trust. W. Thomas London, Stephen E. Cavan,  James
R.  Bordewick, Jr.,  and James  O. Yost, all  of whom  are officers  of MFS, are
officers of the Trust.
 
    MFS has established a strategic alliance with Foreign & Colonial  Management
Ltd.  ("Foreign & Colonial"). Foreign  & Colonial is a  subsidiary of two of the
world's oldest  financial  services  institutions, the  London-based  Foreign  &
Colonial Investment Trust PLC, which pioneered the idea of investment management
in  1868, and HYPO-BANK (Bayerische Hypotheken-und Weschsel-Bank AG), the oldest
publicly listed bank in Germany, founded in 1835. As part of this alliance,  the
portfolio  managers and investment analysts of  MFS and Foreign & Colonial share
their views on  a variety  of investment related  issues, such  as the  economy,
securities   markets,  portfolio   securities  and   their  issuers,  investment
recommendations, strategies and  techniques, risk  analysis, trading  strategies
and  other  portfolio  management  matters.  MFS  has  access  to  the extensive
international equity investment expertise of  Foreign & Colonial, and Foreign  &
Colonial  has access to  the extensive U.S. equity  investment expertise of MFS.
MFS and Foreign Colonial each have investment personnel working in each  other's
offices in Boston and London, respectively.
 
    In  certain  instances there  may  be securities  which  are suitable  for a
Series' portfolio as well as for portfolios  of other clients of MFS or  clients
of  Foreign  &  Colonial.  Some simultaneous  transactions  are  inevitable when
several clients  receive investment  advice  from MFS  and Foreign  &  Colonial,
particularly  when the same security is suitable for more than one client. While
in some cases this arrangement could have  a detrimental effect on the price  or
availability  of the security as  far as a Series  is concerned, in other cases,
however, it may produce increased investment opportunities for the Series.
 
    From time to time, the Adviser  may purchase, redeem and exchange shares  of
any  Series. The  purchase by  the Adviser of  shares of  a Series  may have the
effect of  lowering that  Series' expense  ratio, while  the redemption  by  the
Adviser  of shares of  a Series may  have the effect  of increasing that Series'
expense ratio.
 
    DISTRIBUTOR  --  MFS  Fund  Distributors,  Inc.  ("MFD"),  a  wholly   owned
subsidiary  of MFS, is the distributor of  shares of each Series and also serves
as distributor for certain of the other mutual funds managed by MFS.
 
    ADMINISTRATOR  --  MFS  provides  the  Series  with  certain  administrative
services  pursuant to a Master Administrative  Services Agreement dated March 1,
1997. Under  this Agreement,  MFS provides  the Series  with certain  financial,
legal, compliance, shareholder communications and other administrative services.
As  a partial reimbursement for the cost of providing these services, the Series
pays MFS an administrative  fee up to  0.015% per annum  of the Series'  average
daily  net assets,  provided that  the administrative fee  is not  assessed on a
Series' assets that exceed $3 billion.
 
    SHAREHOLDER SERVICING AGENT  -- MFS Service  Center, Inc. (the  "Shareholder
Servicing  Agent"), a wholly owned subsidiary  of MFS, performs transfer agency,
certain dividend disbursing agency and other services for each Series.
 
                                       23
<PAGE>
8.  INFORMATION CONCERNING SHARES OF EACH SERIES
 
PURCHASES AND REDEMPTIONS
 
    The  separate accounts of the Participating Insurance Companies place orders
to purchase and redeem shares of each  Series based on, among other things,  the
amount of premium payments to be invested and surrender and transfer requests to
be  effected on that day pursuant to Contracts. Orders received by the Trust are
effected on days on which the Exchange is open for trading. For orders  received
by  the Trust before  the close of  regular trading on  the Exchange (normally 4
p.m. eastern time), such purchases and redemptions of the shares of each  Series
are  effected at the respective net asset  values per share determined as of the
close of  regular  trading on  the  Exchange  on that  same  day.  Participating
Insurance  Companies shall be the designee of  the Trust for receipt of purchase
and redemption orders from Contract holders  and receipt by such designee  shall
constitute receipt by the Trust; provided that the Trust receives notice of such
order  by 9:30 a.m. eastern time on the next following day on which the Exchange
is open for trading. Payment for shares shall be by federal funds transmitted by
wire and must be received by 2:00 p.m. eastern time on the next following day on
which the Exchange  is open for  trading after the  purchase order is  received.
Redemption  proceeds shall be by federal funds  transmitted by wire and shall be
sent by 2:00 p.m. eastern time on  the next following day on which the  Exchange
is  open for trading after  the redemption order is  received. No fee is charged
the shareholders when they redeem Series shares.
 
    The offering of shares of any Series  may be suspended for a period of  time
and  each  Series reserves  the  right to  refuse  any specific  purchase order.
Purchase orders may be refused if, in the Adviser's opinion, they are of a  size
that  would disrupt the management of a  Series. The Trust may suspend the right
of redemption of shares of any Series  and may postpone payment for any  period:
(i) during which the Exchange is closed other than customary weekend and holiday
closings  or during which trading  on the Exchange is  restricted; (ii) when the
SEC determines  that a  state of  emergency  exists which  may make  payment  or
transfer  not reasonably practicable; (iii)  as the SEC may  by order permit for
the protection of the security  holders of the Trust; or  (iv) at any time  when
the  Trust may, under applicable laws, rules and regulations, suspend payment on
the redemption of its shares.
 
    Should any conflict between Contract holders arise which would require  that
a  substantial  amount  of net  assets  be  withdrawn from  any  Series, orderly
portfolio management  could be  disrupted  to the  potential detriment  of  such
Contract.
 
NET ASSET VALUE
 
    The  net asset value per share of  each Series is determined each day during
which the Exchange is open for  trading. This determination is made once  during
each  such day as of  the close of regular trading  on the Exchange by deducting
the amount of the Series' liabilities from  the value of the Series' assets  and
dividing  the  difference by  the number  of shares  of the  Series outstanding.
Values of assets in  a Series' portfolio  are determined on  the basis of  their
market or other fair value (amortized cost value in the case of the Money Market
Series),  as described in  the SAI. All investments,  assets and liabilities are
expressed in U.S. dollars based upon current currency exchange rates.
 
DISTRIBUTIONS
 
    Substantially all of  each Series'  net investment income  for any  calendar
year  is declared as dividends  and paid to its  shareholders as dividends on an
annual basis. In addition, each Series may make one or more distributions during
the calendar year to its shareholders from any long-term capital gains, and  may
also  make one or more distributions to its shareholders from short-term capital
gains. In determining the  net investment income  available for distribution,  a
Series  may rely on projections of  its anticipated net investment income (which
may include  short-term capital  gains from  the sales  of securities  or  other
assets,  and, if  allowed by  a Series'  investment restrictions,  premiums from
options written), over  a longer  term, rather  than its  actual net  investment
income for the period.
 
    Shareholders of any of the Series may elect to receive dividends and capital
gain distributions in either cash or additional shares.
 
TAX STATUS
 
    Each  Series of the Trust is treated as a separate entity for federal income
tax purposes. In  order to  minimize the taxes  each Series  would otherwise  be
required  to  pay, each  Series intends  to  qualify each  year as  a "regulated
investment company" under Subchapter M of the Internal Revenue Code of 1986,  as
amended ("the Code"). Because each Series
 
                                       24
<PAGE>
intends  to distribute all of its net investment income and net capital gains to
its shareholders in accordance with the timing requirements imposed by the Code,
it is not expected that any of the  Series will be required to pay entity  level
federal income or excise taxes.
 
    Shares  of  the  Series  are offered  only  to  the  Participating Insurance
Companies' separate accounts  that fund Contracts.  See the applicable  Contract
prospectus  for a  discussion of  the federal  income tax  treatment of  (1) the
separate accounts that purchase  and hold Series shares  and (2) the holders  of
the  Contracts  that  are funded  through  those  accounts. In  addition  to the
diversification requirements  of Subchapter  M  of the  Code, each  Series  also
intends  to diversify its assets as required  by Code Section 817(h)(1), and the
regulations thereunder. See also "Tax Status" in the SAI.
 
DESCRIPTION OF SHARES, VOTING RIGHTS AND LIABILITIES
 
    Each Series currently has one class of shares, entitled Shares of Beneficial
Interest (without par  value). The Trust  has reserved the  right to create  and
issue  additional classes  and series  of shares,  in which  case each  class of
shares of a  series would  participate equally  in the  earnings, dividends  and
assets  attributable to that  class of that  particular series. Shareholders are
entitled to one vote for each share held, and shares of each Series are entitled
to vote  separately to  approve  investment advisory  agreements or  changes  in
investment  restrictions with respect  to that Series, but  shares of all Series
vote together  in  the  election  of  Trustees  and  selection  of  accountants.
Additionally,  each Series will vote separately on any other matter that affects
solely that Series, but  will otherwise vote together  with all other Series  on
all  other  matters.  The  Trust  does not  intend  to  hold  annual shareholder
meetings. The Declaration of Trust provides  that a Trustee may be removed  from
office  in  certain instances.  See "Description  of  Shares, Voting  Rights and
Liabilities" in the SAI.
 
    Each share of  a Series represents  an equal proportionate  interest in  the
Series  with each  share, subject to  the liabilities of  the particular Series.
Shares have no pre-emptive or conversion rights. Shares are fully paid and  non-
assessable.  Should a Series  be liquidated, shareholders  are entitled to share
PRO RATA in the  net assets available for  distribution to shareholders.  Shares
will  remain on  deposit with the  Shareholder Servicing  Agent and certificates
will not be issued.
 
    The Trust  is an  entity of  the  type commonly  known as  a  "Massachusetts
business  trust." Under  Massachusetts law,  shareholders of  such a  trust may,
under certain  circumstances, be  held  personally liable  as partners  for  its
obligations.  However, the  risk of  a shareholder  incurring financial  loss on
account of  shareholder liability  is  limited to  circumstances in  which  both
inadequate insurance existed (E.G., fidelity bonding and omission insurance) and
the Trust itself was unable to meet its obligations.
 
    United  of Omaha Life Insurance Company, Omaha,  NE owns 33.02% of the World
Governments Series' shares,  and, therefore,  controls the  Series; CG  Variable
Annuity--Separate  Account  II, Hartford,  CT owns  44.85%  of the  Total Return
Series and 29.08% of the Utilities Series' shares, and, therefore, controls such
Series;  Ameritas  Life  Insurance  Company--Separate  Account  VA-2  (Annuity),
Lincoln,  NE,  owns  56.16% of  the  Utilities Series'  shares,  and, therefore,
controls the  Series;  and Century  Life  of America--Century  Variable  Annuity
Account,  Waverly, IA, owns 45.82% of the World Governments Series' shares, and,
therefore, controls the Series.
 
PERFORMANCE INFORMATION
 
    Each Series' performance may be quoted in advertising in terms of yield  and
total  return. Performance is based on historical results and is not intended to
indicate future performance. Performance quoted for a Series includes the effect
of deducting that  Series' expenses, but  may not include  charges and  expenses
attributable  to any particular insurance  product. Excluding these charges from
quotations of a Series' performance has the effect of increasing the performance
quoted. Performance for a Series will vary based on, among other things, changes
in market conditions, the level of interest  rates and the level of the  Series'
expenses.  For further information about the  Series' performance for the fiscal
year ended December 31, 1996, please see  the Series' Annual Reports. A copy  of
these   Annual  Reports  may  be  obtained  without  charge  by  contacting  the
Shareholder Servicing Agent (see back cover for address and phone number).
 
    From time to time,  quotations of a  Series' total return  and yield may  be
included  in  advertisements, sales  literature  or reports  to  shareholders or
prospective investors. The total return of a Series refers to return assuming an
investment has been  held in the  Series for one  year and for  the life of  the
Series  (the ending date of  which will be stated).  The total return quotations
may be expressed in terms  of average annual or  cumulative rates of return  for
all  periods quoted.  Average annual total  return refers to  the average annual
compound rate of return  of an investment in  a Series. Cumulative total  return
represents  the cumulative change  in value of  an investment in  a Series. Both
will assume that all dividends and
 
                                       25
<PAGE>
capital gains distributions were reinvested. The yield of a Series refers to net
investment income generated by a Series  over a specified 30-day (or one  month)
period.  This  income  is  then  "annualized." That  is,  the  amount  of income
generated by the Series during that 30-day  (or one month) period is assumed  to
be  generated over a 12-month  period and is shown as  a percentage of net asset
value.
 
EXPENSES
 
    The Trust pays the compensation of the Trustees who are not officers of  MFS
and  all expenses of each Series (other than those assumed by MFS) including but
not limited to: governmental fees;  interest charges; taxes; membership dues  in
the  Investment Company Institute allocable to each Series; fees and expenses of
independent auditors, of legal counsel, and of any transfer agent, registrar  or
dividend disbursing agent of each Series; expenses of repurchasing and redeeming
shares  and servicing shareholder accounts;  expenses of preparing, printing and
mailing  prospectuses,  periodic  reports,  notices  and  proxy  statements   to
shareholders  and to governmental officers  and commissions; brokerage and other
expenses connected with  the execution,  recording and  settlement of  portfolio
security transactions; insurance premiums; fees and expenses of Investors Bank &
Trust Company, the Trust's Custodian, for all services to each Series, including
safekeeping of funds and securities and maintaining required books and accounts;
expenses  of  calculating the  net asset  value  of shares  of each  Series; and
expenses  of   shareholder  meetings.   Expenses  relating   to  the   issuance,
registration  and qualification  of shares of  each Series  and the preparation,
printing and mailing of  prospectuses are borne by  each Series except that  the
Distribution Agreement with MFD requires MFD to pay for prospectuses that are to
be  used for sales purposes. Expenses of the Trust which are not attributable to
a specific  Series are  allocated between  the Series  in a  manner believed  by
management of the Trust to be fair and equitable.
 
    Subject  to termination or revision  at the sole discretion  of MFS, MFS has
agreed to bear expenses of each of  the Series such that the respective  Series'
"Other Expenses," which are defined to include all expenses of the Series except
for  management fees, do not exceed 0.25% of the average daily net assets of the
Series (the "Maximum Percentage"). The obligation of MFS to bear these  expenses
for  a Series terminates on the last day of the Series' fiscal year in which its
"Other Expenses" are less than or equal to the Maximum Percentage. The  payments
made  by MFS  on behalf  of each  Series under  this arrangement  are subject to
reimbursement by the Series to MFS, which will be accomplished by the payment of
an expense reimbursement fee by the Series to MFS computed and paid monthly at a
percentage of the Series' average daily  net assets for its then current  fiscal
year,  with a limitation that immediately  after such payment the Series' "Other
Expenses" will not exceed the Maximum Percentage. This expense reimbursement  by
each  Series to MFS terminates on the earlier of the date on which payments made
by the Series equal the  prior payment of such  reimbursable expenses by MFS  or
December 31, 2004.
 
SHAREHOLDER COMMUNICATIONS
 
    Owners  of Contracts issued  by Participating Insurance  Companies for which
shares of one or more  Series are the investment  vehicle will receive from  the
Participating  Insurance Companies semi-annual  financial statements and audited
year-end financial  statements certified  by the  Trust's independent  certified
public accountants. Each report will show the investments owned by the Trust and
the  valuations thereof  as determined  by the  Trustees and  will provide other
information about the Trust and its operations.
 
    Participating Insurance  Companies with  inquiries regarding  the Trust  may
call  the Trust's Shareholder  Servicing Agent. (See back  cover for address and
phone number.)
                              -------------------
 
    The SAI for the Trust,  dated May 1, 1997,  as amended or supplemented  from
time  to  time, contains  more detailed  information about  each of  the Series,
including information related to: (i)  the investment policies and  restrictions
of each Series; (ii) the Trustees, officers and investment adviser of the Trust;
(iii)  portfolio transactions; (iv) the shares  of each Series, including rights
and liabilities of  shareholders; (v)  the method  used to  calculate yield  and
total  rate of return quotations  of each Series; (vi)  the determination of net
asset value  of  shares of  each  Series; and  (vii)  certain voting  rights  of
shareholders of each Series.
 
                                       26
<PAGE>
                                                                      APPENDIX A
 
                          DESCRIPTION OF BOND RATINGS
 
The ratings of Moody's, S&P and Fitch represent their opinions as to the quality
of  various debt instruments. It should be emphasized, however, that ratings are
not absolute standards of quality. Consequently, debt instruments with the  same
maturity,  coupon and rating may have different yields while debt instruments of
the same maturity and coupon with different ratings may have the same yield.
 
                        MOODY'S INVESTORS SERVICE, INC.
 
    AAA: Bonds which are rated  Aaa are judged to be  of the best quality.  They
carry  the smallest degree of  investment risk and are  generally referred to as
"gilt edged." Interest payments are protected by a large or by an  exceptionally
stable margin and principal is secure. While the various protective elements are
likely  to change, such changes as can be visualized are most unlikely to impair
the fundamentally strong position of such issues.
 
    AA: Bonds  which are  rated Aa  are  judged to  be of  high quality  by  all
standards. Together with the Aaa group they comprise what are generally known as
high  grade bonds. They are  rated lower than the  best bonds because margins of
protection may  not  be  as  large  as in  Aaa  securities  or  fluctuations  of
protective  elements may be of greater amplitude  or there may be other elements
present which  make the  long-term  risks appear  somewhat  larger than  in  Aaa
securities.
 
    A:  Bonds which are rated A possess many favorable investment attributes and
are to be considered as upper-medium-grade obligations. Factors giving  security
to  principal and interest are considered  adequate, but elements may be present
which suggest a susceptibility to impairment sometime in the future.
 
    BAA: Bonds which are  rated Baa are  considered as medium-grade  obligations
(I.E.,  they are neither highly protected nor poorly secured). Interest payments
and principal security appear  adequate for the  present but certain  protective
elements  may be lacking or may  be characteristically unreliable over any great
length of time. Such  bonds lack outstanding  investment characteristics and  in
fact have speculative characteristics as well.
 
    BA:  Bonds which are rated Ba are judged to have speculative elements; their
future cannot be considered  as well-assured. Often  the protection of  interest
and  principal payments  may be very  moderate and thereby  not well safeguarded
during both  good  and  bad  times over  the  future.  Uncertainty  of  position
characterizes bonds in this class.
 
    B:  Bonds which are rated B  generally lack characteristics of the desirable
investment. Assurance of interest  and principal payments  or of maintenance  of
other terms of the contract over any long period of time may be small.
 
    CAA:  Bonds which are rated Caa are of  poor standing. Such issues may be in
default or there may be present elements of danger with respect to principal  or
interest.
 
    CA:  Bonds which are rated Ca represent obligations which are speculative in
a  high  degree.  Such  issues  are  often  in  default  or  have  other  marked
shortcomings.
 
    C: Bonds which are rated C are the lowest rated class of bonds and issues so
rated  can be regarded as having extremely  poor prospects of ever attaining any
real investment standing.
 
    ABSENCE OF RATING: Where no rating has  been assigned or where a rating  has
been  suspended or withdrawn, it may be  for reasons unrelated to the quality of
the issue.
 
    Should no rating be assigned, the reason may be one of the following:
 
    1.  an application for rating was not received or accepted;
 
    2.  the issue or issuer belongs  to a group of securities or companies  that
       are not rated as a matter of policy;
 
    3.  there is a lack of essential data pertaining to the issue or issuer; or
 
    4.    the  issue was  privately  placed, in  which  case the  rating  is not
       published in Moody's publications.
 
    Suspension or withdrawal may occur if new and material circumstances  arise,
the  effects  of which  preclude satisfactory  analysis; if  there is  no longer
available reasonable up-to-date  data to permit  a judgment to  be formed; if  a
bond is called for redemption; or for other reasons.
 
                                      A-1
<PAGE>
                       STANDARD & POOR'S RATINGS SERVICES
 
    AAA:  Debt rated AAA has the highest rating assigned by S&P. Capacity to pay
interest and repay principal is extremely strong.
 
    AA: Debt rated  AA has  a very  strong capacity  to pay  interest and  repay
principal and differs from the highest rated issues only in small degree.
 
    A:  Debt rated A has a strong  capacity to pay interest and repay principal,
although it is somewhat  more susceptible to the  adverse effects of changes  in
circumstances and economic conditions than debt in higher-rated categories.
 
    BBB:  Debt  rated BBB  is regarded  as  having an  adequate capacity  to pay
interest and repay principal. Whereas  it normally exhibits adequate  protection
parameters,  adverse  economic  conditions or  changing  circumstances  are more
likely to lead to a  weakened capacity to pay  interest and repay principal  for
debt in this category than in higher-rated categories.
 
    BB:  Debt rated  BB has less  near-term vulnerability to  default than other
speculative issues. However, it faces major ongoing uncertainties or exposure to
adverse  business,  financial,  or  economic  conditions  which  could  lead  to
inadequate  capacity  to meet  timely interest  and  principal payments.  The BB
rating category  is also  used for  debt  subordinated to  senior debt  that  is
assigned an actual or implied BBB- rating.
 
    B: Debt rated B has a greater vulnerability to default but currently has the
capacity  to meet interest payments  and principal repayments. Adverse business,
financial or economic conditions will  likely impair capacity or willingness  to
pay  interest and repay principal.  The B rating category  is also used for debt
subordinated to senior  debt that is  assigned an  actual or implied  BB or  BB-
rating.
 
    CCC:  Debt rated CCC has a  currently identifiable vulnerability to default,
and is dependent upon favorable  business, financial and economic conditions  to
meet  timely payment  of interest  and repayment of  principal. In  the event of
adverse business, financial, or  economic conditions, it is  not likely to  have
the  capacity to pay  interest and repay  principal. The CCC  rating category is
also used for debt  subordinated to senior  debt that is  assigned an actual  or
implied B or B- rating.
 
    CC:  The rating CC is typically applied  to debt subordinated to senior debt
that is assigned an actual or implied CCC rating.
 
    C: The rating  C is typically  applied to debt  subordinated to senior  debt
which  is assigned an  actual or implied CCC-  debt rating. The  C rating may be
used to cover a situation where a  bankruptcy petition has been filed, but  debt
service payments are continued.
 
    CI: The rating CI is reserved for income bonds on which no interest is being
paid.
 
    D:  Debt rated D is  in payment default. The D  rating category is used when
interest payments or principal payments  are not made on  the date due, even  if
the  applicable  grace period  has not  expired, unless  S&P believes  that such
payments will be made during such grace  period. The D rating also will be  used
upon  the  filing  of  a  bankruptcy  petition  if  debt  service  payments  are
jeopardized.
 
    PLUS (+) OR MINUS  (-): The ratings from  AA to CCC may  be modified by  the
addition  of a  plus or minus  sign to  show relative standing  within the major
rating categories.
 
    NR: Indicates  that no  public  rating has  been  requested, that  there  is
insufficient  information on which to base a rating, or that S&P does not rate a
particular type of obligation as a matter of policy.
 
A-1 AND P-1 COMMERCIAL PAPER RATINGS
 
Description of S&P, Fitch and Moody's highest commercial paper ratings:
 
    The rating "A" is  the highest commercial paper  rating assigned by S&P  and
Fitch,  and issues  so rated  are regarded as  having the  greatest capacity for
timely payment. Issues in the "A" category are delineated with the numbers 1,  2
and  3 to indicate the relative degree  of safety. The A-1 designation indicates
that the degree  of safety regarding  timely payment is  either overwhelming  or
very  strong.  Those  A-1  issues  determined  to  possess  overwhelming  safety
characteristics will be denoted with a plus (+) sign designation.
 
                                      A-2
<PAGE>
    The rating P-1 is the highest  commercial paper rating assigned by  Moody's.
Issuers  rated P-1 have a superior ability for repayment. P-1 repayment capacity
will normally be evidenced by the following characteristics: (1) leading  market
positions  in well  established industries;  (2) high  rates of  return on funds
employed; (3) conservative  capitalization structure with  moderate reliance  on
debt and ample asset protection; (4) broad margins in earnings coverage of fixed
financial  charges and high  internal cash generation;  and (5) well established
access to  a  range  of  financial markets  and  assured  sources  of  alternate
liquidity.
 
                         FITCH INVESTORS SERVICE, INC.
 
    AAA:  Bonds  considered to  be investment  grade and  of the  highest credit
quality. The obligor  has an exceptionally  strong ability to  pay interest  and
prepay  principal, which  is unlikely to  be affected  by reasonably foreseeable
events.
 
    AA: Bonds considered to be investment grade and of very high credit quality.
The obligor's  ability to  pay  interest and  repay  principal is  very  strong,
although  not quite as strong  as bonds rated 'AAA'.  Because bonds rated in the
'AAA' and 'AA' categories are not significantly vulnerable to foreseeable future
developments, short-term debt of these issuers is generally rated 'F-1+'.
 
    A: Bonds considered to be investment grade and of very high credit  quality.
The  obligor's ability to pay  interest and repay principal  is considered to be
strong, but may be more vulnerable to adverse changes in economic conditions and
circumstances than bonds with higher ratings.
 
    BBB: Bonds  considered to  be investment  grade and  of satisfactory  credit
quality. The obligor's ability to pay interest and repay principal is considered
to  be  adequate.  Adverse  changes in  economic  conditions  and circumstances,
however, are more likely to have  adverse impact on these bonds and,  therefore,
impair  timely payment. The likelihood that the ratings of these bonds will fall
below investment grade is higher than for bonds with higher ratings.
 
    BB: Bonds are considered speculative. The obligor's ability to pay  interest
and  repay  principal may  be affected  over time  by adverse  economic changes.
However, business  and  financial alternatives  can  be identified  which  could
assist the obligor in satisfying its debt service requirements.
 
    B:  Bonds are considered  highly speculative. While bonds  in this class are
currently meeting debt service requirements, the probability of continued timely
payment of  principal and  interest  reflects the  obligor's limited  margin  of
safety and the need for reasonable business and economic activity throughout the
life of the issue.
 
    CCC: Bonds have certain identifiable characteristics which, if not remedied,
may  lead to default.  The ability to meet  obligations requires an advantageous
business and economic environment.
 
    CC: Bonds are  minimally protected.  Default in payment  of interest  and/or
principal seems probable over time.
 
    C: Bonds are in imminent default in payment of interest of principal.
 
    PLUS(+)  MINUS(-): Plus  and minus  signs are used  with a  rating symbol to
indicate the relative position of a  credit within the rated category. Plus  and
minus signs, however, are not used in the 'AAA' category.
 
    NR: indicates that Fitch does not rate the specific issue.
 
    CONDITIONAL:  A conditional rating is  premised on the successful completion
of a project or the occurrence of a specific event.
 
    SUSPENDED: A rating is suspended when Fitch deems the amount of  information
available from the issuer to be inadequate for rating purposes.
 
    WITHDRAWN:  A rating will be withdrawn when an issue matures or is called or
refinanced, and, at Fitch's discretion, when  an issuer fails to furnish  proper
and timely information.
 
    FITCHALERT:  Ratings  are placed  on FitchAlert  to  notify investors  of an
occurrence that is likely to result in a rating change and the likely  direction
of  such  change.  These are  designated  a "Positive,"  indicating  a potential
upgrade, "Negative," for potential downgrade,  or "Evolving," where ratings  may
be lowered. FitchAlert is relatively short-term and should be resolved within 12
months.
 
                                      A-3
<PAGE>
                                                                      APPENDIX B
 
                  PRINCIPAL SECTORS OF THE UTILITIES INDUSTRY
 
The  principal sectors of the utility industry in which the Utilities Series may
invest are discussed below.
 
ELECTRIC -- The electric utility industry consists of companies that are engaged
principally in  the  generation,  transmission  and  sale  of  electric  energy,
although  many  also provide  other  energy-related services.  Domestic electric
utility companies, in general,  recently have been  favorably affected by  lower
fuel  and financing costs and the full  or near completion of major construction
programs. In  addition, many  of these  companies recently  have generated  cash
flows  in excess  of current  operating expenses  and construction expenditures,
permitting some  degree of  diversification  into unregulated  businesses.  Some
electric  utilities have also taken advantage of the right to sell power outside
of their traditional geographic  areas. Electric utility companies  historically
have  been subject  to the  risks associated  with increases  in fuel  and other
operating  costs,  high  interest  costs   on  borrowings  needed  for   capital
construction  programs, costs associated with  compliance with environmental and
safety regulations and changes in the regulatory climate.
 
    In the U.S., the construction and  operation of nuclear power facilities  is
subject  to  increased scrutiny  by, and  evolving  regulations of,  the Nuclear
Regulatory  Commission  and  state  agencies  having  comparable   jurisdiction.
Increased  scrutiny might  result in higher  operating costs  and higher capital
expenditures, with the risk that the regulators may disallow inclusion of  these
costs  in rate authorizations or the risk that a company may not be permitted to
operate or  complete  construction of  a  facility. In  addition,  operators  of
nuclear power plants may be subject to significant costs for disposal of nuclear
fuel and for the de-commissioning of such plants.
 
TELECOMMUNICATIONS  -- The telephone industry  is large and highly concentrated.
Companies that distribute telephone services and provide access to the telephone
networks comprise the greatest portion  of this segment. Telephone companies  in
the U.S. are still experiencing the effects of the breakup of American Telephone
&  Telegraph Company, which  occurred in 1984. Since  1984, companies engaged in
telephone communication services  have expanded  their non-regulated  activities
into  other businesses, including cellular  telephone services, data processing,
equipment retailing,  computer software  and  hardware services,  and  financial
services.  This  expansion has  provided  significant opportunities  for certain
telephone companies to  increase their  earnings and dividends  at faster  rates
than   had  been  allowed  in  traditionally  regulated  businesses.  Increasing
competition, technological innovations  and other  structural changes,  however,
could adversely affect the profitability of such utilities.
 
GAS  --  Gas  transmission companies  and  gas distribution  companies  are also
undergoing significant changes. In  the U.S., interstate transmission  companies
are regulated by the Federal Energy Regulatory Commission, which is reducing its
regulation  of the  industry. Many companies  have diversified into  oil and gas
exploration and development, making returns more sensitive to energy prices.  In
the  recent  decade,  gas  utility companies  have  been  adversely  affected by
disruptions in  the  oil industry  and  have  also been  affected  by  increased
concentration   and  competition.  In  the  opinion  of  the  Adviser,  however,
environmental considerations  could  improve the  gas  industry outlook  in  the
future.  For example, natural gas is the  cleanest of the hydrocarbon fuels, and
this may result in incremental shifts in fuel consumption toward natural gas and
away from oil and coal.
 
WATER -- Water supply utilities  are companies that collect, purify,  distribute
and  sell  water. In  the  U.S. and  around the  world,  the industry  is highly
fragmented because  most  of  the  supplies  are  owned  by  local  authorities.
Companies  in this industry are generally  mature and are experiencing little or
no per capita volume growth.
 
                              -------------------
 
    There can  be  no assurance  that  the positive  developments  noted  above,
including those relating to changing regulation, will occur or that risk factors
other than those noted above will not develop in the future.
 
                                      B-1
<PAGE>
INVESTMENT ADVISER
Massachusetts Financial Services Company
500 Boylston Street, Boston, MA 02116
(617) 954-5000
(800) 637-8730
 
DISTRIBUTOR
MFS Fund Distributors, Inc.
500 Boylston Street, Boston, MA 02116
(617) 954-5000
CUSTODIAN
Investors Bank & Trust Company
89 South Street, Boston, MA 02111
 
DIVIDEND DISBURSING AGENT
State Street Bank and Trust Company
225 Franklin Street, Boston, MA 02110
 
SHAREHOLDER SERVICING AGENT
MFS Service Center, Inc.
500 Boylston Street, Boston, MA 02116
Toll free: (800) 343-2829, ext. 3500
MAILING ADDRESS:
P.O. Box 1400, Boston, MA 02104-9985
INDEPENDENT AUDITORS
Deloitte & Touche LLP
125 Summer Street, Boston, MA 02110
 
                      ------------------------------------
                       MFS-REGISTERED TRADEMARK- EMERGING
                                 GROWTH SERIES
                        MFS-REGISTERED TRADEMARK- TOTAL
                                 RETURN SERIES
                      MFS-REGISTERED TRADEMARK- UTILITIES
                                     SERIES
                        MFS-REGISTERED TRADEMARK- WORLD
                               GOVERNMENTS SERIES
 
                                     [LOGO]
 
                                   PROSPECTUS
 
                                  MAY 1, 1997
 
                                     [LOGO]
 
                MFS-REGISTERED TRADEMARK- EMERGING GROWTH SERIES
                 MFS-REGISTERED TRADEMARK- TOTAL RETURN SERIES
                   MFS-REGISTERED TRADEMARK- UTILITIES SERIES
               MFS-REGISTERED TRADEMARK- WORLD GOVERNMENTS SERIES
                     500 Boylston Street, Boston, MA 02116
 
                            ------------------------


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