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                                                                  EXHIBIT 4F (1)

                                 AMENDMENT NO. 1
                     TO 364-DAY CREDIT AGREEMENT AND WAIVER

         This Amendment No. 1 to 364-day Credit Agreement and Waiver (this
"Amendment") is entered into as of February 8, 1999, by and among Dexter
Corporation, a Connecticut corporation (the "Borrower"), The First National Bank
of Chicago, individually and as agent ("Agent"), and the other financial
institutions signatory hereto.

                                    RECITALS

         A. The Borrower, the Agent and the Lenders are party to that certain
364-day credit agreement dated as of December 15, 1998 (the "Credit Agreement").
Unless otherwise specified herein, capitalized terms used in this Amendment
shall have the meanings ascribed to them by the Credit Agreement.

         B. The Borrower, the Agent and the undersigned Required Lenders wish to
amend the Credit Agreement on the terms and conditions set forth below.

         Now, therefore, in consideration of the mutual execution hereof and
other good and valuable consideration, the parties hereto agree as follows:

                  1. Amendment to Credit Agreement. The Credit Agreement is
hereby amended as follows:

                           (a) Section 6.10(i) of the Credit Agreement is
         amended in its entirety to read as follows:

                  "(i) any Subsidiary may declare and pay dividends or make
                  distributions to its shareholders ratably relative to their
                  respective ownership interests in such Subsidiary and".

                  2. Consent and Waiver. The Required Lenders hereby waive any
Unmatured Default or Default existing under the Credit Agreement (including any
Unmatured Default or Default arising out of a breach of Sections 6.3(a) or 6.10)
which would not have arisen had this Amendment been in effect at all times since
December 15, 1998.

                  3. Representations and Warranties of the Borrower. The
Borrower represents and warrants that:

                           (a) The execution, delivery and performance by the
         Borrower of this Amendment have been duly authorized by all necessary
         corporate action and that this Amendment is a legal, valid and binding
         obligation of the Borrower enforceable against the Borrower in
         accordance with its terms, except as the enforcement thereof may be
         subject to the effect of any applicable bankruptcy, insolvency,
         reorganization, moratorium or similar law affecting creditors' rights
         generally;

                           (b) Each of the representations and warranties
         contained in the Credit Agreement is true and correct in all material
         respects on and as of the date hereof as if made on the date hereof;

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                           (c) After giving effect to this Amendment, no Default
         or Unmatured Default has occurred and is continuing.

                  4. Effective Date. This Amendment shall become effective upon
the execution and delivery hereof by the Borrower, the Agent and the Required
Lenders.

                  5. Reference to and Effect Upon the Credit Agreement.

                           (a) Except as specifically amended, the Credit
         Agreement and the other Loan Documents shall remain in full force and
         effect and are hereby ratified and confirmed.

                           (b) The execution, delivery and effectiveness of this
         Amendment shall not operate as a waiver of any right, power or remedy
         of the Agent or any Lender under the Credit Agreement or any Loan
         Document, nor constitute a waiver of any provision of the Credit
         Agreement or any Loan Document, except as specifically set forth
         herein. Upon the effectiveness of this Amendment, each reference in the
         Credit Agreement to "this Agreement", "hereunder", "hereof", "herein"
         or words of similar import shall mean and be a reference to the Credit
         Agreement as amended hereby.

                  6. Costs and Expenses.

                           The Borrower hereby affirms its obligation under
         Section 9.7 of the Credit Agreement to reimburse the Agent for all
         reasonable costs, internal charges and out-of-pocket expenses paid or
         incurred by the Agent in connection with the preparation, negotiation,
         execution and delivery of this Amendment, including but not limited to
         the attorneys' fees and time charges of attorneys for the Agent with
         respect thereto.

                  7. GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE INTERNAL LAWS (AS OPPOSED TO CONFLICTS OF LAWS
PROVISIONS) OF THE STATE OF ILLINOIS BUT GIVING EFFECT TO FEDERAL LAWS
APPLICABLE TO NATIONAL BANKS.

                  8. Headings. Section headings in this Amendment are included
herein for convenience of reference only and shall not constitute a part of this
Amendment for any other purposes.

                  9. Counterparts. This Amendment may be executed in any number
of counterparts, each of which when so executed shall be deemed an original but
all such counterparts shall constitute one and the same instrument.

                           (signature page to follow)

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                  IN WITNESS WHEREOF, the parties have executed this Amendment
as of the date and year first above written.


                                       DEXTER CORPORATION
                                       By:       /s/ Dale J. Ribaudo
                                       Name:     Dale J. Ribaudo
                                       Title:    Treasurer

                                       THE FIRST NATIONAL BANK OF CHICAGO,
                                       Individually and as Agent
                                       By:       /s/ Tom Dao
                                       Name:     Tom Dao
                                       Title:    Corporate Banking Officer

                                       FLEET BANK,
                                       Individually and as Syndication Agent
                                       By:       /s/ Marlene R. Haddad
                                       Name:     Marlene R. Haddad
                                       Title:    Senior Vice President

                                       BANK OF AMERICA NATIONAL TRUST AND
                                       SAVINGS ASSOCIATION,
                                       Individually and as Documentation Agent
                                       By:       /s/ Donald J. Chin
                                       Name:     Donald J. Chin
                                       Title:    Managing Director

                                       ABN AMRO BANK N.V.,
                                       Individually and as Co-Agent
                                       By:       /s/ James S. Adelsheim
                                       Name:     James S. Adelsheim
                                       Title:    Group Vice President

                                       By:       /s/ David A. Carroll
                                       Name:     David A. Carroll
                                       Title:    Officer

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                                       BANKBOSTON, N.A.,
                                       Individually and as Co-Agent
                                       By: /s/ Harvey H. Thayer, Jr.
                                       Name: Harvey H. Thayer, Jr.
                                       Title: Managing Director

                                       BANCA COMMERCIALE ITALIANA,
                                       NEW YORK BRANCH,
                                       Individually and as Co-Agent
                                       By:       /s/ Charles Dougherty
                                       Name:     Charles Dougherty
                                       Title:    Vice President

                                       By:       /s/ Karen Purelis
                                       Name:     Karen Purelis
                                       Title:    Vice President

                                       THE BANK OF NEW YORK
                                       By:       /s/ Kenneth P. Sneider, Jr.
                                       Name:     Kenneth P. Sneider, Jr.
                                       Title:    Vice President

                                       WACHOVIA BANK, N.A.
                                       By:       /s/ Henry H. Hagan
                                       Name:     Henry H. Hagan
                                       Title:    Senior Vice President

                                       per pro BROWN BROTHERS HARRIMAN & CO.
                                       By:       /s/ Jared S. Keyes
                                       Name:     Jared S. Keyes
                                       Title:    Manager

                                       COMMERZBANK AG,
                                       Individually and as Co-Agent
                                       By:       /s/ Robert Donohue
                                       Name:     Robert Donohue
                                       Title:    Senior Vice President

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                                       By:       /s/ Peter Doyle
                                       Name:     Peter Doyle
                                       Title:    Assistant Vice President

                                       DEN DANSKE BANK AKTIESELSKAB,
                                       CAYMAN ISLANDS BRANCH,
                                       Individually and as Co-Agent
                                       By:       /s/ Peter L. Hargraves
                                       Name:     Peter L. Hargraves
                                       Title:    Vice President

                                       By:       /s/ John A. O'Neill
                                       Name:     John A. O'Neill
                                       Title:    Vice President

                                       FIRST UNION NATIONAL BANK,
                                       Individually and as Co-Agent
                                       By:       /s/ Stephen T. Dorosh
                                       Name:     Stephen T. Dorosh
                                       Title:    Vice President

                                       MELLON BANK, N.A.,
                                       Individually and as Co-Agent
                                       By:       /s/ Mark Ricci
                                       Name:     Mark Ricci
                                       Title:    Banking Officer

                                       SUNTRUST BANK, ATLANTA,
                                       Individually and as Co-Agent
                                       By:       /s/ W. David Wisdom
                                       Name:     W. David Wisdom
                                       Title:    Vice President

                                       By:       /s/ Robin R. Cowan
                                       Name:     Robin R. Cowan
                                       Title:    Operations Officer

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                                       BANQUE NATIONALE DE PARIS
                                       By:       /s/ Richard L. Sted
                                       Name:     Richard L. Sted
                                       Title:    Senior Vice President

                                       By:       /s/ Sophie Revillard Kaufman
                                       Name:     Sophie Revillard Kaufman
                                       Title:    Vice President