AMENDMENT NO. 2 TO AGREEMENT AND PLAN OF MERGER

         This Amendment No. 2 to Agreement and Plan of Merger (this "AMENDMENT")
is made as of August 25, 2000, by and among Genzyme Corporation, a Massachusetts
corporation ("GENZYME"), Seagull Merger Corporation, a Massachusetts corporation
and a wholly owned subsidiary of Genzyme ("SEAGULL"), and Biomatrix, Inc., a
Delaware corporation ("BIOMATRIX").

         WHEREAS, the parties have entered into that certain Agreement and Plan
of Merger dated as of March 6, 2000 (as amended by Amendment No. 1 thereto,
dated April 17, 2000, the "MERGER AGREEMENT"), which provides that Biomatrix be
merged with and into Seagull on the terms and subject to the conditions set
forth in the Merger Agreement; and

         WHEREAS, the parties wish to amend the terms of the Merger Agreement;

         NOW, THEREFORE, in consideration of the foregoing, the parties agree as
follows:

         1.       Section 10.1(a) of the Merger Agreement is hereby deleted in
its entirety and replaced with the following:

                  (a)      by either Biomatrix or Genzyme, by written notice to
         the other, if the Effective Time shall not have occurred on or before
         October 31, 2000 (the "Outside Date"); provided, however, that the
         right to terminate this Agreement under this Section 10.1(a) shall not
         be available to any party whose breach of a representation or warranty
         or failure to fulfill any covenant or agreement under this Agreement
         has been the cause of or resulted in the failure of the Merger to occur
         on or before such date; and provided, further, however, that on October
         30, 2000, either party, by written notice to the other, may extend the
         Outside Date to a date that is not later than November 15, 2000, if
         such party is in the process of soliciting proxies for the Biomatrix
         Stockholders Meeting or the Genzyme Stockholders Meeting, as the case
         may be;

         2.       Genzyme, Seagull and Biomatrix each represents and warrants
that it has full corporate power and authority to enter into this Amendment; and
that all corporate action on its part necessary to authorize this Amendment
(other than the approval of the Merger (as defined in the Merger Agreement)), as
contemplated by Section 10.5 of the Merger Agreement, has been taken.

         3.       Except as expressly modified hereby, the Merger Agreement
shall remain in full force and effect in accordance with its original terms.

         4.       This Amendment shall be governed, construed and enforced in
accordance with the laws of the Commonwealth of Massachusetts, without regard to
principles of conflicts of laws, except to the extent that the laws of the State
of




Delaware apply to the Merger and the rights of stockholders of Biomatrix
relative to the Merger.

         5.       This Amendment may be executed in two or more counterparts,
each of which shall be deemed an original, and all of which together shall
constitute one and the same instrument.

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                                       2


         IN WITNESS WHEREOF, the parties have executed this Amendment No. 2 to
Agreement and Plan of Merger as of the date first stated above.

                               GENZYME CORPORATION


                               By:      /s/ Earl M. Collier, Jr.
                                  -------------------------------------------
                                     Earl M. Collier, Jr.
                                     Executive Vice President


                               SEAGULL MERGER CORPORATION


                               By:      /s/ Earl M. Collier, Jr.
                                  -------------------------------------------
                                     Earl M. Collier, Jr.
                                     President


                               By:      /s/ David B. Johnston
                                  -------------------------------------------
                                     David B. Johnston
                                     Treasurer


                               BIOMATRIX, INC.


                               By:      /s/ Endre A. Balazs
                                  -------------------------------------------
                                     Endre A. Balazs
                                     Chief Executive Officer and Chief
                                     Scientific Officer



                               By:      /s/ Rory B. Riggs
                                  -------------------------------------------
                                     Rory B. Riggs
                                     President


                               By:      /s/ Maxine Seifert
                                  -------------------------------------------
                                     Maxine Seifert
                                     Vice President, Finance, Chief Financial
                                     Officer and Treasurer