<PAGE>

                                                                   Exhibit 4.9


THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED, OR THE SECURITIES LAWS OF ANY STATE OF
THE UNITED STATES. THE SECURITIES REPRESENTED HEREBY MAY NOT BE OFFERED OR SOLD
OR OTHERWISE TRANSFERRED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT
FOR THE SECURITIES UNDER APPLICABLE SECURITIES LAWS OR UNLESS OFFERED, SOLD OR
TRANSFERRED PURSUANT TO AN AVAILABLE EXEMPTION FROM THE REGISTRATION
REQUIREMENTS OF THOSE LAWS.


                    COMMON STOCK PURCHASE WARRANT CERTIFICATE

                              Dated: March 20, 1998

                to Purchase ___________ Shares of Common Stock of

                         GENZYME TRANSGENICS CORPORATION

      Genzyme Transgenics Corporation, a Massachusetts corporation (the
"Company"), hereby certifies that ______________________, its permissible
transferees, designees, successors and assigns (collectively, the "Holder"), for
value received, is entitled to purchase from the Company at any time commencing
on March 20, 1998 ("Issuance Date") and terminating on the fourth anniversary of
the Issuance Date (or such earlier date as is specified in a duly delivered Call
Notice (as defined below)) up to _______________________ shares (each a "Share"
and collectively the "Shares") of the Company's common stock (the "Common
Stock"), at an exercise price of $15.1563 per Share (the "Exercise Price"). The
number of Shares purchasable hereunder and the Exercise Price are subject to
adjustment as provided in Section 4 hereof.

      1.    Exercise of Warrants.

            (a) Upon presentation and surrender of this Common Stock Purchase
Warrant Certificate ("Warrant Certificate" or "Certificate"), or Lost
Certificate Affidavit (as defined below), accompanied by a completed Election to
Purchase in the form attached hereto as Exhibit A (the "Election to Purchase")
duly executed, at the principal office of the Company at Five Mountain Road,
Framingham, MA 01701, Attn: Secretary, together with a check payable to the
Company in the amount of the Exercise Price multiplied by the number of Shares
being purchased, the Company or the Company's Transfer Agent as the case may be,
shall, within two (2) trading days of receipt of the foregoing, deliver to the
Holder hereof, certificates of fully paid and non-assessable Common Stock which
in the aggregate represent the number of Shares being purchased; provided,
however, that the Holder may elect, with the prior written consent of the
Company, which may be granted or withheld in the Company's sole discretion on a
case by case basis, to utilize the cashless exercise provisions
<PAGE>

set forth below in lieu of tendering the Exercise Price in cash. The
certificates so delivered shall be in such denominations as may be reasonably
requested by the Holder and shall be registered in the name of the Holder or
such other name as shall be designated by the Holder. All or less than all of
the Warrants represented by this Certificate may be exercised and, in case of
the exercise of less than all, the Company, upon surrender hereof, will at the
Company's expense deliver to the Holder a new Warrant Certificate or
Certificates (in such denominations as may be requested by the Holder) of like
tenor and dated the date hereof entitling said holder to purchase the number of
Shares represented by this Certificate which have not been exercised and to
receive Registration Rights with respect to such Shares, and all other rights
with respect to the shares which the Holder has on the date hereof.

            (b) Cashless Exercise. Notwithstanding the foregoing provision
regarding payment of the Exercise Price in cash, the Holder may elect, with the
prior written consent of the Company, which may be granted or withheld in the
Company's sole discretion on a case by case basis, to receive a reduced number
of Shares in lieu of tendering the Exercise Price in cash ("Cashless Exercise");
provided that the Holder shall be entitled, without the consent of the Company,
to elect Cashless Exercise at any time that the resale of the Warrant Shares by
the holder is not then registered pursuant to an effective registration
statement under the Securities Act of 1933, as amended (the "Securities Act"),
at any time when registration is so required pursuant to the Registration Rights
Agreement (as defined below). In such case, the number of Shares to be issued to
the Holder shall be computed using the following formula;:

                        X = Y(A-B)/A

where:      X = the number of Shares to be issued to the Holder;
            Y = the number of Shares to be exercised under this Warrant
                Certificate; 
            A = the Market Value (defined below) of one share of Common
                Stock; and 
            B = the Exercise Price.

As used herein, " Market Value" refers to the closing bid price of the Common
Stock (as reported by Bloomberg, L.P.) on the day before the Election to
Purchase and this Warrant Certificate are duly surrendered to the Company for a
full or partial exercise hereof. Notwithstanding the foregoing definition, if
the Common Stock is not listed on a national securities exchange or quoted in
the Nasdaq System at the time said Election to Purchase is submitted to the
Company in the foregoing manner, the Market Value of the Common Stock shall be
(a) determined in good faith by the Board of Directors of the Company and
certified in a board resolution, based on the most recently completed
arm's-length transaction between the Company and a Person other than an
affiliate of the Company or between any two such Persons and the closing of
which occurs on such date or shall have occurred within the six-month period
preceding such date, or (b) if no such transaction shall have occurred within
the six-month period, the value of the security as determined by an independent
financial expert, unless the Company shall become subject to a merger,
acquisition, or other consolidation pursuant to which the Company is not the
surviving entity, in which case the Market Value
<PAGE>

of the Common Stock shall be deemed to be the value received per share by the
Company's common stockholders pursuant to such merger, acquisition or other
consolidation.

      2. Exchange, Transfer and Replacement. (a) At any time prior to the
exercise hereof, this Warrant Certificate may be exchanged upon presentation and
surrender to the Company, alone or with other Warrant Certificates of like tenor
of different denominations registered in the name of the same Holder, together
with a duly executed Assignment in substantially the form and substance of the
Form of Assignment which accompanies this Warrant Certificate. The Warrant
Certificate or Certificates shall be exchanged for another Warrant Certificate
or Certificates of like tenor in the name of such Holder and/or the transferees
named in such Assignment, exercisable for the aggregate number of Shares as the
Certificate or Certificates surrendered, provided that the Company shall not be
obligated to issue exchange or transfer Certificates for an exchange or transfer
of less than 10,000 shares. The Company shall issue any Warrant Certificates
reflecting such transfer or assignment (including such portion of this Warrant
Certificate, if any, as shall not have been transferred or assigned) within
three (3) business days after receipt of the requisite Warrant Certificate(s)
and duly completed Assignment.

            (b) Replacement of Warrant Certificate. Upon receipt of evidence
reasonably satisfactory to the Company of the loss, theft, destruction, or
mutilation of this Warrant Certificate and, in the case of any such loss, theft,
or destruction, upon delivery of an indemnity agreement reasonably satisfactory
in form and amount to the Company (collectively, a "Lost Certificate
Affidavit"), or, in the case of any such mutilation, upon surrender and
cancellation of this Warrant Certificate, the Company, at its expense, will
execute and deliver in lieu thereof, a new Warrant Certificate of like tenor.

            (c) Cancellation; Payment of Expenses. Upon the surrender of this
Warrant Certificate in connection with any transfer, exchange or replacement as
provided in this Section 2, this Warrant Certificate shall be promptly canceled
by the Company. The Company shall pay all taxes (other than securities transfer
taxes) and all other expenses (other than legal expenses, if any, incurred by
the Holder or transferees) and charges payable in connection with the
preparation, execution and delivery of Warrant Certificates pursuant to this
Section 2.

            (d) Warrant Register. The Company shall maintain, at its principal
executive offices (or at the offices of the transfer agent for the Warrant
Certificate or such other office or agency of the Company as it may designate by
notice to the holder hereof), a register for this Warrant Certificate (the
"Warrant Register"), in which the Company shall record the name and address of
the person in whose name this Warrant Certificate has been issued, as well as
the name and address of each permitted transferee and each prior owner of this
Warrant Certificate.

            (e) Company Call Right. Beginning on the business day following the
first anniversary of the Issuance Date, provided that the twenty consecutive
trading day average closing bid price of the Common Stock the Company for the
period ending on the date prior to delivery of such notice (as reported by
Bloomberg, L.P.) is equal to or greater than 140%
<PAGE>

of the Exercise Price, as adjusted pursuant to Section 4 hereof, the Company
shall have the ability to deliver a written notice to the Holder hereof (a "Call
Notice"). The Call Notice shall specify a date no less than 30 days following
the date of delivery of such Call Notice, and, unless exercised prior to such
date, this Certificate (or any unexercised portion hereof) shall expire, and
Holder shall have no further rights hereunder, on and following such specified
date. The Holder shall have the right to exercise its rights hereunder during
such 30 day notice period.

      3. Rights and Obligations of Holders of this Certificate. The Holder of
this Certificate shall not, by virtue hereof, be entitled to any rights of a
stockholder in the Company, either at law or in equity; provided, however, that
in the event any certificate representing shares of Common Stock or other
securities is issued to the holder hereof upon exercise of some or all of the
Warrants, such holder shall, for all purposes, be deemed to have become the
holder of record of such Common Stock on the date on which this Certificate,
together with a duly executed Purchase Form, was surrendered and payment of the
aggregate Exercise Price was made, irrespective of the date of delivery of such
share certificate.

      4.    Adjustments.

            (a) Stock Dividends, Reclassifications, Recapitalizations, Etc. In
the event the Company: (i) pays a dividend in Common Stock or makes a
distribution in Common Stock, (ii) subdivides its outstanding Common Stock into
a greater number of shares, (iii) combines its outstanding Common Stock into a
smaller number of shares or (iv) increases or decreases the number of shares of
Common Stock outstanding by reclassification of its Common Stock (including a
recapitalization in connection with a consolidation or merger in which the
Company is the continuing corporation), then (1) the Exercise Price on the
record date of such division or distribution or the effective date of such
action shall be adjusted by multiplying such Exercise Price by a fraction, the
numerator of which is the number of shares of Common Stock outstanding
immediately before such event and the denominator of which is the number of
shares of Common Stock outstanding immediately after such event, and (2) the
number of shares of Common Stock for which this Warrant Certificate may be
exercised immediately before such event shall be adjusted by multiplying such
number by a fraction, the numerator of which is the Exercise Price immediately
before such event and the denominator of which is the Exercise Price immediately
after such event.

            (b) Cash Dividends and Other Distributions. In the event that at any
time or from time to time the Company shall distribute to all holders of Common
Stock (i) any dividend or other distribution of cash, evidences of its
indebtedness, shares of its capital stock or any other properties or securities
or (ii) any options, warrants or other rights to subscribe for or purchase any
of the foregoing (other than in each case, (w) the issuance of any rights under
a shareholder rights plan, (x) any dividend or distribution described in Section
4(a), (y) any rights, options, warrants or securities described in Section 4(c)
and (z) any cash dividends or other cash distributions from current earnings),
then the number of shares of Common Stock issuable upon the exercise of each
Warrant Certificate shall be increased to a number determined by multiplying the
number of shares of Common Stock issuable upon the exercise
<PAGE>

of such Warrant Certificate immediately prior to the record date for any such
dividend or distribution by a fraction, the numerator of which shall be such
Current Market Value (as hereinafter defined) per share of Common Stock on the
record date for such dividend or distribution, and the denominator of which
shall be such Current Market Value per share of Common Stock on the record date
for such dividend or distribution less the sum of (x) the amount of cash, if
any, distributed per share of Common Stock and (y) the fair value (as determined
in good faith by the Board of Directors of the Company, whose determination
shall be evidenced by a board resolution, a copy of which will be sent to the
Holders upon request) of the portion, if any, of the distribution applicable to
one share of Common Stock consisting of evidences of indebtedness, shares of
stock, securities, other property, warrants, options or subscription or purchase
rights; and the Exercise Price shall be adjusted to a number determined by
dividing the Exercise Price immediately prior to such record date by the above
fraction. Such adjustments shall be made whenever any distribution is made and
shall become effective as of the date of distribution, retroactive to the record
date for any such distribution. No adjustment shall be made pursuant to this
Section 4(b) which shall have the effect of decreasing the number of shares of
Common Stock issuable upon exercise of each Warrant Certificate or increasing
the Exercise Price.

            (c) Rights Issue. In the event that at any time or from time to time
the Company shall issue rights, options or warrants entitling the holders
thereof to subscribe for shares of Common Stock, or securities convertible into
or exchangeable or exercisable for Common Stock to all holders of Common Stock
(other than in connection with the adoption of a shareholder rights plan by the
Company) without any charge, entitling such holders to subscribe for or purchase
shares of Common Stock at a price per share that as of the record date for such
issuance is less than the then Current Market Value per share of Common Stock,
the number of shares of Common Stock issuable upon the exercise of each Warrant
Certificate shall be increased to a number determined by multiplying the number
of shares of Common Stock theretofore issuable upon exercise of each Warrant
Certificate by a fraction, the numerator of which shall be the number of shares
of Common Stock outstanding on the date of issuance of such rights, options,
warrant or securities plus the number of additional shares of Common Stock
offered for subscription or purchase or into or for which such securities that
are issued are convertible, exchangeable or exercisable, and the denominator of
which shall be the number of shares of Common Stock outstanding on the date of
issuance of such rights, option, warrants or securities plus the total number of
shares of Common Stock which the aggregate consideration expected to be received
by the Company (assuming the exercise or conversion of all such rights, options,
warrants or securities) would purchase at the then Current Market Value per
share of Common Stock. In the event of any such adjustment, the Exercise Price
shall be adjusted to a number determined by dividing the Exercise price
immediately prior to such date of issuance by the aforementioned fraction. Such
adjustment shall be made immediately after such rights, options or warrants are
issued and shall become effective, retroactive to the record date for the
determination of stockholders entitled to receive such rights, options, warrants
or securities. No adjustment shall be made pursuant to this Section 4(c) which
shall have the effect of decreasing the number of shares of Common Stock
purchasable upon exercise or each Warrant Certificate or of increasing the
Exercise Price.
<PAGE>

            (d) Combination: Liquidation. (i) Except as provided in Section
4(d)(ii) below, in the event of a Combination (as defined below), each Holder
shall have the right to receive upon exercise of the Warrant Certificates the
kind and amount of shares of capital stock or other securities or property which
such Holder would have been entitled to receive upon or as a result of such
Combination had such Warrant Certificate been exercised immediately prior to
such event (subject to further adjustment in accordance with the terms hereof).
Unless paragraph (ii) is applicable to a Combination, the Company shall provide
that the surviving or acquiring Person (the "Successor Company") in such
Combination will assume by written instrument the obligations under this Section
4 and the obligations to deliver to the Holder such shares of stock, securities
or assets as, in accordance with the foregoing provisions, the Holder may be
entitled to acquire. The provisions of this Section 4(d)(i) shall similarly
apply to successive Combinations involving any Successor Company. "Combination"
means an event in which the Company consolidates with, mergers with or into, or
sells all or substantially all of its assets to another Person, where "Person"
means any individual, corporation, partnership, joint venture, limited liability
company, association, joint-stock company, trust, unincorporated organization,
government or any agency or political subdivision thereof or any other entity.

            (ii) In the event of (x) a Combination where consideration to the
holders of Common Stock in exchange for their shares is payable solely in cash
or (y) the dissolution, liquidation or winding-up of the Company, the Holders
shall be entitled to receive, upon surrender of their Warrant Certificates,
distributions on an equal basis with the holders of Common Stock or other
securities issuable upon exercise of the Warrant Certificates, as if the Warrant
Certificates had been exercised immediately prior to such event, less the
Exercise Price. In case of any Combination described in this Section 4(d)(ii),
the surviving or acquiring Person and, in the event of any dissolution,
liquidation or winding-up of the Company, the Company, shall deposit promptly
following the consummation of such combination or at the time of such
dissolution, liquidation or winding-up with an agent or trustee for the benefit
of the Holders of the funds, if any, necessary to pay to the Holders the amounts
to which they are entitled as described above. After such funds and the
surrendered Warrant Certificates are received, the Company is required to
deliver a check in such amount as is appropriate (or, in the case of
consideration other than cash, such other consideration as is appropriate) to
such Person or Persons as it may be directed in writing by the Holders
surrendering such Warrant Certificates.

            (e) Notice of Adjustment. Whenever the Exercise Price or the number
of shares of Common Stock and other property, if any, issuable upon exercise of
the Warrant Certificates is adjusted, as herein provided, the Company shall
deliver to the holders of the Warrant Certificates in accordance with Section 10
a certificate of the Company's Chief Financial Officer setting forth, in
reasonable detail, the event requiring the adjustment and the method by which
such adjustment was calculated (including a description of the basis on which
(i) the Board of Directors determined the fair value of any evidences of
indebtedness, other securities or property or warrants, options or other
subscription or purchase rights and (ii) the Current Market Value of the common
Stock was determined, if either of such determinations were required), and
specifying the Exercise Price and number of shares of
<PAGE>

Common Stock issuable upon exercise of Warrant Certificates after giving effect
to such adjustment.

            (f) Purchase Price Adjustment. In the event that the Company issues
or sells any Common Stock or securities which are convertible into or
exchangeable for its Common Stock or any convertible securities, or any warrants
or other rights to subscribe for or to purchase or any options for the purchase
of its Common Stock or any such convertible securities (other than shares or
options issued or which may be issued pursuant to the Company's employee or
director option plans or shares issued upon exercise of options, warrants or
rights outstanding on the date of the Agreement and listed in the Company's most
recent periodic report filed under the Exchange Act) at a purchase price per
share on the date of original issuance of such security which is less than 95%
of the Current Market Value of the Common Stock on the trading day next
preceding such issue or sale, then in each such case, the Exercise Price in
effect immediately prior to such issue or sale shall be reduced effective
concurrently with such issue or sale to an amount determined by multiplying the
Exercise Price then in effect by a fraction, (x) the numerator of which shall be
the sum of (1) the number of shares of Common Stock outstanding immediately
prior to such issue or sale, plus (2) the number of shares of Common Stock which
the aggregate consideration received by the Company for such additional shares
would purchase at such Current Market Value ; and (y) the denominator of which
shall be the number of shares of Common Stock of the Company outstanding
immediately after such issue or sale.

For the purposes of the foregoing adjustment, in the case of the issuance of any
convertible securities, warrants, options or other rights to subscribe for or to
purchase or exchange for, shares of Common Stock ("Convertible Securities"), the
maximum number of shares of Common Stock that would be issuable upon exercise,
exchange or conversion of such Convertible Securities (assuming that shares of
Common Stock were trading at the Current Market Value at the time of conversion)
shall be deemed to be outstanding, provided that no further adjustment shall be
made upon the actual issuance of Common Stock upon exercise, exchange or
conversion of such Convertible Securities.

            (g) Notice of Certain Transactions. In the event that the Company
shall propose (a) to pay any dividend payable in securities of any class to the
holders of its Common Stock or to make any other non-cash dividend or
distribution to the holders of its Common Stock, (b) to offer the holders of its
Common Stock rights to subscribe for or to purchase any securities convertible
into shares of Common Stock or shares of stock of any class or any other
securities, rights or options, (c) to effect any capital reorganization,
reclassification, consolidation or merger affecting the class of Common Stock,
as a whole, or (d) to effect the voluntary or involuntary dissolution,
liquidation or winding-up of the Company, the Company shall, within the time
limits specified below, send to each Holder a notice of such proposed action or
offer. Such notice shall be mailed to the Holders at their addresses as they
appear in the Warrant Register (as defined in Section 2(d)), which shall specify
the record date for the purposes of such dividend, distribution or rights, or
the date such issuance or event is to take place and the date of participation
therein by the holders of Common Stock, if any such date is to be fixed, and
shall briefly indicate the effect of such action on the number of shares of
Common Stock and on the number and kind of any other
<PAGE>

shares of stock and on other property, if any, and the number of shares of
Common Stock and other property, if any, issuable upon exercise of each Warrant
Certificate and the Exercise Price after giving effect to any adjustment
pursuant to Section 4 which will be required as a result of such action. Such
notice shall be given as promptly as possible and (x) in the case of any action
covered by clause (a) or (b) above, at least 10 days prior to the record date
for determining holders of the Common Stock for purposes of such action or (y)
in the case of any other such action, at least 20 days prior to the date of the
taking of such proposed action or the date of participation therein by the
holders of Common Stock, whichever shall be the earlier.

            (h) Current Market Value. "Current Market Value" per share of Common
Stock or any other security at any date means (i) if the security is not
registered under the Securities Exchange Act of 1934, as amended (the "Exchange
Act"), (a) the value of the security, determined in good faith by the Board of
Directors of the Company and certified in a board resolution, based on the most
recently completed arm's-length transaction between the Company and a Person
other than an affiliate of the Company or between any two such Persons and the
closing of which occurs on such date or shall have occurred within the six-month
period preceding such date, or (b) if no such transaction shall have occurred
within the six-month period, the value of the security as determined by an
independent financial expert or (ii) if the security is registered under the
Exchange Act, the average of the daily closing bid prices (or the equivalent in
an over-the-counter market) for each day on which the Common Stock is traded for
any period on the principal securities exchange or other securities market on
which the common Stock is being traded (each, a "Trading Day") during the period
commencing ten (10) Trading Days before such date and ending on the date one day
prior to such date, or if the security has been registered under the Exchange
Act for less than ten (10) consecutive Trading Days before such date, the
average of the daily closing bid prices (or such equivalent) for all of the
Trading Days before such date for which daily closing bid prices are available;
provided, however, that if the closing bid price is not determinable for at
least five (5) Trading Days in such period, the "Current Market Value" of the
security shall be determined as if the security were not registered under the
Exchange Act.

            (i) Other Adjustments. In the event of any other transaction of the
type contemplated by this Section 4, but not expressly provided for by the
provisions hereof, the Board of Directors of the Company will make appropriate
adjustment in the Exercise Price so as to equitably protect the rights of the
Holder.

            (j) No Impairment of Holder's Rights. The Company will not, by
amendment of its articles of organization or bylaws or through any
reorganization, transfer of assets, consolidation, merger, dissolution, issue or
sale of securities or any other voluntary action, except as contemplated hereby,
avoid or seek to avoid the observance or performance of any of the terms of this
Warrant Certificate, but will at all times in good faith assist in the carrying
out of all such terms and in the taking of all action as may be necessary or
appropriate in order to protect the rights of the Holder against dilution or
other impairment.
<PAGE>

      5. Company's Representations.

            (a) The Company covenants and agrees that all shares of Common Stock
issuable upon exercise of this Warrant Certificate will, upon delivery, be duly
and validly authorized and issued, fully-paid and non-assessable and free from
all taxes, liens, claims and encumbrances.

            (b) The Company covenants and agrees that it will at all times
reserve and keep available an authorized number of shares of its Common Stock
and other applicable securities sufficient to permit the exercise in full of all
outstanding options, warrants and rights, including this Warrant Certificate.

            (c) The Company shall promptly secure the listing of the Shares upon
each national securities exchange or automated quotation system, if any, upon
which shares of Common Stock are then listed or become listed (subject to
official notice of issuance upon exercise of this Warrant Certificate) and shall
maintain, so long as any other shares of Common Stock shall be so listed, such
listing of all shares of Common Stock from time to time issuable upon the
exercise of this Warrant Certificate; and the Company shall so list on each
national securities exchange or automated quotation system, as the case may be,
and shall maintain such listing of, any other shares of capital stock of the
Company issuable upon the exercise of this Warrant Certificate if and so long as
any shares of the same class shall be listed on such national securities
exchange or automated quotation system.

            (d) The Company has taken all necessary action and proceedings as
required and permitted by applicable law, rule and regulation, including,
without limitation, the notification of the principal market on which the Common
Stock is traded, for the legal and valid issuance of this Warrant Certificate to
the Holder under this Warrant Certificate.

            (e) With a view to making available to Holder the benefits of Rule
144 promulgated under the Act and any other rule or regulation of the Securities
and Exchange Commission ("SEC") that may at any time permit Holder to sell
securities of the Company to the public without registration, the Company agrees
to use its reasonable best efforts to:

                  (i) make and keep public information available, as those terms
are understood and defined in Rule 144, at all times;

                  (ii) file with the SEC in a timely manner all reports and
other documents required of the Company under the Act and the Securities
Exchange Act of 1934, as amended (the "Exchange Act"); and

                  (iii) furnish to any Holder forthwith upon request a written
statement by the Company that it has complied with the reporting requirements of
Rule 144 and of the Act and the Exchange Act, a copy of the most recent annual
or quarterly report of the Company, and such other reports and documents so
filed by the Company as may be
<PAGE>

reasonably requested to permit any such Holder to take advantage of any rule or
regulation of the SEC permitting the selling of any such securities without
registration.

      6. Registration Rights. The initial Holder is entitled to the benefit of
such registration rights in respect of the Shares as are set forth in the
Registration Rights Agreement dated as of March 20, 1998 by and between the
Company, the Holder and the other investors parties thereto ("Registration
Rights Agreement"), including the right to assign such rights to certain
assignees as set forth therein.

      7. Issuance of Certificates. Within two (2) trading days of receipt of a
duly completed Election to Purchase form, together with this Certificate and
payment of the Exercise Price, the Company, at its expense, will cause to be
issued in the name of and delivered to the Holder of this Warrant, a certificate
or certificates for the number of fully paid and non-assessable shares of Common
Stock to which that holder shall be entitled on such exercise. In the event the
shares of Common Stock are not timely delivered to the Holder, the Company
agrees to (a) indemnify Holder for all damages, including consequential and
special damages, lost profits and expenses, including legal fees, and (b)
beginning on the fifth (5th) day following the Company's receipt of a duly
completed Election to Purchase form, pay a default premium of 2% per day of the
value of underlying shares (based on the highest closing price during the two
(2) day period preceding the date of surrender of the Warrant Certificate). In
lieu of issuance of a fractional share upon any exercise hereunder, the Company
will pay the cash value of that fractional share, calculated on the basis of the
Exercise Price. Prior to registration of the resale of the shares of Common
Stock underlying this Warrant Certificate, and delivery of an Election to
Purchase to the Company, all such certificates shall bear a restrictive legend
to the effect that the Shares represented by such certificate have not been
registered under the 1933 Act, and that the Shares may not be sold or
transferred in the absence of such registration or an exemption therefrom, such
legend to be substantially in the form of the bold-face language appearing at
the top of Page 1 of this Warrant Certificate.

      8. Disposition of Warrants or Shares. The Holder of this Warrant
Certificate, each transferee hereof and any holder and transferee of any Shares,
by his or its acceptance thereof, agrees that no public distribution of Warrants
or Shares will be made in violation of the provisions of the 1933 Act.
Furthermore, it shall be a condition to the transfer of the Warrants that any
transferee thereof deliver to the Company his or its written agreement to accept
and be bound by all of the relevant terms and conditions contained in this
Warrant Certificate.

      9. Notices. Except as otherwise specified herein to the contrary, all
notices, requests, demands and other communications required or desired to be
given hereunder shall only be effective if given in writing by certified or
registered U.S. mail with return receipt requested and postage prepaid; by
private overnight delivery service (e.g. Federal Express); by facsimile
transmission (if no original documents or instruments must accompany the
notice); or by personal delivery. Any such notice shall be deemed to have been
given (a) on the business day immediately following the mailing thereof, if
mailed by certified or registered U.S. mail as specified above; (b) on the
business day immediately following deposit with a
<PAGE>

private overnight delivery service if sent by said service; (c) upon receipt of
confirmation of transmission if sent by facsimile transmission; or (d) upon
personal delivery of the notice. All such notices shall be sent to the following
addresses (or to such other address or addresses as a party may have advised the
other in the manner provided in this Section 10):

                  If to the Company:

                  Genzyme Transgenics Corporation
                  One Mountain Road
                  Framingham, MA  01701
                  Attn:  Chief Financial Officer
                  Phone: (508) 270-2579
                  Fax: (508) 270-2303

                  with a copy to:

                  Palmer & Dodge LLP
                  One Beacon Street
                  Boston, MA  02108-3190
                  Attn:  Lynnette C. Fallon, Esq.
                  Phone: (617) 573-0220
                  Fax: (617) 227-4420


                  If to ________________________:
                  
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________

                  and with a copy to:

                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
                  ______________________________
<PAGE>

                  in each case with a copy to:

                  Shoreline Pacific Institutional Finance
                  3 Harbor Drive, Suite 211
                  Sausalito, CA  94965
                  Telephone: (415) 332-7800
                  Telecopy: (415) 332-7808
                  Attention:  General Counsel


Notwithstanding the time of effectiveness of notices set forth in this Section,
an Election to Purchase shall not be deemed effectively given until it has been
duly completed and submitted to the Company together with the original Warrant
Certificate to be exercised and payment of the Exercise Price in a manner set
forth in this Section.

      10. Notwithstanding anything in this Warrant Certificate to the contrary,
in no event shall the holder of this Warrant Certificate be entitled to exercise
with respect to a number of shares of Common Stock to the extent that following
such exercise the sum of (i) the number of shares of Common Stock beneficially
owned by the holder and its affiliates (other than shares of Common Stock which
may be deemed beneficially owned through the ownership of the unexercised
Warrant Certificates and unconverted shares of Preferred Stock (as defined in
the Securities Purchase Agreement)) or other securities containing restrictions
on conversion or exercise analogous to the provisions in this paragraph, and
(ii) the number of shares of Common Stock issuable upon exercise of the Warrant
Certificates (or portions thereof) with respect to which the determination
described herein is being made, would result in beneficial ownership by the
holder and its affiliates of more than 4.99% of the outstanding shares of Common
Stock. For purposes of the immediately preceding sentence, (x) beneficial
ownership shall be determined in accordance with Section 13(d) of the Securities
Exchange Act of 1934, as amended, and Rules 13(d) -(g) thereunder, except as
otherwise provided in clause (i) hereof, and (y) a holder may waive the
limitations set forth herein upon not less than sixty-one (61) days prior
written notice to the Company (with such waiver taking effect only upon the
expiration of such sixty-one (61) day notice period).

      11. Governing Law. This Warrant Certificate and all rights and obligations
hereunder shall be deemed to be made under and governed by the laws of the State
of New York without giving effect to the conflicts of laws provisions. The
Holder hereby irrevocably consents to the venue and jurisdiction of the State
and Federal Courts located in the State of New York, County of New York.

      12. Successors and Assigns. This Warrant Certificate shall be binding upon
and shall inure to the benefit of the parties hereto and their respective
successors and permitted assigns.

      13. Headings. The headings of various sections of this Warrant Certificate
have been inserted for reference only and shall not affect the meaning or
construction of any of the provisions hereof.
<PAGE>

      14. Severability. If any provision of this Warrant Certificate is held to
be unenforceable under applicable law, such provision shall be excluded from
this Warrant Certificate, and the balance hereof shall be interpreted as if such
provision were so excluded.

      15. Modification and Waiver. This Warrant Certificate and any provision
hereof may be amended, waived, discharged or terminated only by an instrument in
writing signed by the Company and the Holder.

      16. Specific Enforcement. The Company and the Holder acknowledge and agree
that irreparable damage would occur in the event that any of the provisions of
this Warrant Certificate were not performed in accordance with their specific
terms or were otherwise breached. It is accordingly agreed that the parties
shall be entitled to an injunction or injunctions to prevent or cure breaches of
the provisions of this Warrant Certificate and to enforce specifically the terms
and provisions hereof, this being in addition to any other remedy to which
either of them may be entitled by law or equity.


                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
<PAGE>

Genzyme Transgenics Corporation: Common Stock Purchase Warrant Certificate


      IN WITNESS WHEREOF, the Company has caused this Warrant Certificate to be
duly executed, manually or by facsimile, by one of its officers thereunto duly
authorized.

                         GENZYME TRANSGENICS CORPORATION


Date:  March 20, 1998               By:/s/ John B. Green
                                       ----------------------------------
                                       Name:  John B. Green
                                       Title: Vice President, Treasurer
<PAGE>

                              ELECTION TO PURCHASE

                          To Be Executed by the Holder
                      in Order to Exercise the Common Stock
                          Purchase Warrant Certificate

      The undersigned Holder hereby elects to exercise _______ of the Warrants
represented by the attached Common Stock Purchase Warrant Certificate, and to
purchase the shares of Common Stock issuable upon the exercise of such Warrants,
and requests that certificates for securities be issued in the name of:

           __________________________________________________________
                     (Please type or print name and address)

           __________________________________________________________

           __________________________________________________________

           __________________________________________________________
                 (Social Security or Tax Identification Number)

and delivered to:______________________________________________________________

_______________________________________________________________________________.

            (Please type or print name and address if different from above)

If such number of Warrants being exercised hereby shall not be all the Warrants
evidenced by the attached Common Stock Purchase Warrant Certificate, a new
Common Stock Purchase Warrant Certificate for the balance of such Warrants shall
be registered in the name of, and delivered to, the Holder at the address set
forth below.

      [In full payment of the purchase price with respect to the Warrants
exercised and transfer taxes, if any, the undersigned hereby tenders payment of
$__________ by check, money order or wire transfer payable in United States
currency to the order of Genzyme Transgenics Corporation.] or [The undersigned
elects cashless exercise in accordance with Section 1(b) of the Common Stock
Purchase Warrant Certificate.]
<PAGE>

      Holder hereby represents and convenants that it has complied with, or will
comply with, any and all prospectus delivery requirements with respect to its
sale of the Common Stock of the Company being purchased herewith.


                                    HOLDER:


Dated:_________________________     By:_________________________________
                                        Name:
                                        Title:
                                        Address: _______________________
                                                 _______________________
                                                 _______________________
<PAGE>

                               FORM OF ASSIGNMENT
                   (To be signed only on transfer of Warrant)


For value received, the undersigned hereby sells, assigns, and transfers unto
_____________ the right represented by the within Warrant to purchase ______
shares of Common Stock of Genzyme Transgenics Corporation, a Massachusetts
corporation, to which the within Warrant relates, and appoints
____________________ Attorney to transfer such right on the books of Genzyme
Transgenics Corporation, a Massachusetts corporation, with full power of
substitution of premises.


Dated:_________________                         By: __________________________
                                                    Name:
                                                    Title:
                                                (signature must conform to name
                                          of holder as specified on the fact
                                          of the Warrant)

                                                Address: _____________________
                                                ______________________________
                                                ______________________________


Signed in the presence of :


____________________________

<PAGE>

                               Schedule of Holders


Warrant Holder                             No. of Shares Issuable Under Warrant
--------------                             ------------------------------------

Shepherd Investments International, Ltd.               100,000
c/o Staro Asset Management
1500 West Market Street, Suite 200
Mequon, WI  53092

Stark International                                    100,000
c/o Staro Asset Management
1500 West Market Street, Suite 200
Mequon, WI 53092

RGC International Investors, LDC                       200,000
c/o Rose Glen Capital Management, L.P.
3 Bala Plaza East, Suite 200
251 St. Asaphs Road
Bala Cynwyd, PA  19004