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                                                                 EXHIBIT 10.56


                                PROMISSORY NOTE


Newton, Massachusetts                                        September 6, 1996


        FOR VALUE RECEIVED, I, Michael Tarnow (the "Borrower"), unconditionally
promise to pay to Creative BioMolecules, Inc., a Massachusetts corporation
having offices at 45 South Street, Hopkinton, Massachusetts (the "Lender"), or
order, the Principal Sum of Three Hundred Fifty Thousand Dollars ($350,000.00),
with interest at the rate of 6.02% per annum, payable in arrears, as follows:

        (a) The Principal Sum of Three Hundred Fifty Thousand Dollars
        ($350,000.00), shall be payable in three annual installments as follows:

            i.    The first installment of One Hundred Sixteen Thousand Six
                  Hundred Sixty Six Dollars ($116,666.00) shall be due on
                  September 6, 1997;

            ii.   The second installment of One Hundred Sixteen Thousand Six
                  Hundred Sixty Seven Dollars ($116,667.00) shall be due on
                  September 4, 1998; and

            iii.  The third installment of One Hundred Sixteen Thousand Six
                  Hundred Sixty Seven Dollars ($116,677.00) shall be due on
                  September 4, 1999.

        (b) With each payment of an installment to principal, as set forth
        above, the Borrower shall also pay to the Lender accrued interest on the
        entire outstanding principal balance at the rate of 6.02% per annum from
        the date of this instrument.

        Notwithstanding any contrary provision of this instrument, the entire
principal sum, or any unpaid balance thereof shall be due and payable with all
accrued interest as hereinabove set forth twelve (12) months after the date of
the termination for any reason whatsoever of the undersigned's employment with
Creative BioMolecules, Inc. and its affiliates. For purposes hereof, an
"affiliate" means Creative BioMolecules, Inc. and any of its 100% owned
subsidiaries and any of its or their successors in business.

        The undersigned agrees to pay all costs and expenses, including all
attorney fees, for the collection of this note upon default, and to pay interest
on all amounts not paid when due (pursuant to the terms hereof, by acceleration,
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otherwise) at the rate of one and one-half (1 1/2%) per cent per month until
paid in full. The undersigned further agrees that if this note is not paid in
full when due, the balance due, including interest, may be offset against and
withheld from any amounts, including salary, due to the undersigned from the
holder. All payments shall be made at the office of the holder at 45 South
Street, Hopkinton, Massachusetts, or at such other place as the holder hereof
may from time to time designate in writing.

      At the option of the holder, this note shall become immediately due and
payable without notice or demand upon the occurrence at any time of any of the
following events: (1) default in any payment of principal or interest due
hereunder or in the performance or observance of the terms of conditions of any
mortgage, security agreement, or other instrument or agreement (including
amendments and extensions thereof) securing this note; (2) default in the
payment or performance of any other liability or obligation of the undersigned
or of any indorser or guarantor of any liability or obligation of the
undersigned to holder; or (3) if any party liable hereon, whether as maker,
indorser, guarantor, surety or otherwise shall die, make an assignment for
benefit of creditors, or if a receiver of any such party's property shall be
appointed, or if a petition in bankruptcy or other similar proceeding under any
law for relief of debtors shall be filed by or against any such party.

      Each and every party liable hereon, either as a maker, indorser,
guarantor, surety or otherwise, hereby (1) waives presentment, demand, protest
and notice of every kind and description, and all suretyship defenses and
defenses in the nature thereof; (2) waives any defenses based upon, and
specifically assents to, any and all extensions and postponements of the time of
payment and all other indulgences and forebearances which may be granted by the
holder to any party hereon; (3) agrees to any substitution, exchange, release,
surrender or other delivery of any collateral held hereunder and to the addition
or release of any other party or person primarily or secondarily liable; and (4)
agrees to be bound by all the terms contained in this note and agrees that the
obligations and agreements of all such parties shall be joint and several.

      No delay or omission on the part of the holder in exercising any right
hereunder shall operate as waiver of such right or of any other right of such
holder, nor shall any delay, omission or waiver on any one occasion be deemed a
bar to or waiver of the alteration or modification of the terms of this note
shall be valid unless in writing signed by the holder of this note and only to
the extent therein set forth.

      Any default under this note or in the performance and observance of the
provisions of any mortgage, security agreement,

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or other agreement pertaining thereto shall be deemed a default on all other
notes, obligations and liabilities of all parties liable hereon to the holder,
whether now existing or hereafter arising, and any default on any other note,
obligation or liability of any party liable hereon to the holder, whether now
existing or hereafter arising, shall also be deemed a default under this note.

      No single or partial exercise of any power hereunder or under any mortgage
or security agreement securing this note shall preclude other or future exercise
thereof or the exercise of any other power. The holder hereof shall at all times
have the right to proceed against any portion of the security held herefore in
such order and in such manner as the holder may see fit, without waiving any
rights with respect to any other security.

      All times of payment of principal, interest or any other monies due under
or in respect of this note or under or in respect to any mortgage, security
agreement or other instrument or agreement securing this note shall be of the
strict essence, provided, however, that all indebtedness evidenced by this note
may be prepaid in whole or in part at any time without penalty.

      If any term or provision of this note, or any portion of any such term or
provision, shall be held invalid or against public policy, or if the application
of the same to any person or circumstance is held invalid or against public
policy, then the remainder of this note (or the remainder of such term or
provision) and the application thereof to other persons or circumstances shall
not be affected thereby and shall remain valid and in full force and effect to
the fullest extent permitted by the law.

      All rights and obligations hereunder shall be governed by the laws of the
Commonwealth of Massachusetts and this note is executed as and shall have the
effect of a sealed instrument. Notwithstanding any provision herein or in any
instrument now or hereafter securing this note, the total liability for payments
in the nature of interest shall not exceed the limitations now imposed by the
applicable laws of the state whose laws are

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controlling on the subject as shall be determined by final order of a court of
competent jurisdiction.

      EXECUTED as an instrument under seal as of the date and year first above
written.

Signed in the presence of:


/s/Catherine S. Stamps                    /s/Michael Tarnow
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                                          Michael Tarnow

      Secured by a mortgage of the real estate known as Unit 1, 191 Commonwealth
Avenue, Boston, Massachusetts, recorded with the Suffolk County Registry of
Deeds.

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