EXHIBIT 10.1
                              CONSULTING AGREEMENT

      This Consulting Agreement is made as of October 1, 1981, between Repligen
Corporation (the "Company"), a Delaware corporation having its principal place
of business at 50 Staniford Street, Boston, Massachusetts 02114 and Dr. Paul R.
Schimmel (the "Consultant") of 44 Sanderson Road, Lexington, Massachusetts
02173.

      Consultant is a founding stockholder of the Company and has developed
expertise in recombinant DNA technology which he desires to make available to
the Company. The Company desires to obtain the benefit of Consultant's expertise
in recombinant DNA technology.

      NOW, THEREFORE, for good and valuable consideration, the receipt of which
is hereby acknowledged, Consultant and the Company agree as follows:

1. CONSULTING SERVICES

      This Agreement shall have an initial term of five years beginning on
October 1, 1981, and continuing until September 30, 1986. Thereafter, this
Agreement shall be automatically extended for successive terms of one year each
unless written notice that this Agreement shall terminate on the next
anniversary date is given by one party to the other at least 90 days before that
date.

      During the term of this Agreement, the Company agrees to pay Consultant a
monthly consulting fee of $2,000 per month through July 1982 and $1,000 per
month thereafter, payable on or about the first day of each month, far
consulting services to be provided by him under this Agreement. The monthly
consulting fee may be increased upon annual review by a majority of the
disinterested members of the Board of Directors of the Company.

      In addition to the payment of such consulting fees, the Company will
reimburse Consultant for all travel and living expenses incurred by him as a
result of his performance of consulting services under this Agreement. The
Company shall also provide Consultant with an automobile for use on the
Company's business and will pay all insurance, maintenance and operating
expenses associated therewith.

      In consideration of the payment of the monthly consulting fee described
above, Consultant agrees to make himself available not less than two days each
month to consult with officers and scientists of the Company as requested from
time to time by an appropriate official of the Company and at specific dates
mutually agreed upon in advance.

      Consultant agrees that (i) during the term of this Agreement and (ii) for
a period of up to one year immediately following the termination of this
Agreement for any reason if, at the option of the Company, it pays Consultant,
in a lump sum, an amount equal to 90% of the consulting fees paid to him by the
Company for the preceding 12 months, Consultant shall not directly or
indirectly, except as a passive investor in publicly held companies and except
for investments held at the date hereof, engage in, or own or control any
interest in, or act as a director, officer or employee of, or consultant or



scientific advisor to, any firm, corporation or institution directly or
indirectly (a) engaged in a business substantially similar to that of the
Company or any of its subsidiaries or (b) in competition with the Company or any
of its subsidiaries. Consultant further agrees that during the term of this
Agreement he will not undertake any new commitments as a director, officer or
employee of, or consultant or scientific advisor to, any commercial, for-profit
firm, corporation or institution, whether or not engaged in competition with or
in a business substantially similar to that of the Company.

      Nothing in the preceding paragraph shall prohibit Consultant from being a
member of the faculty or staff of a university, college or other educational or
non-profit research institution and performing the attendant and customary
obligations of such position.

      The Company may permit Consultant to engage in the prohibited activities
described in this section upon such conditions, if any, as the Company may deem
appropriate. Such permission shall be set forth in a written instrument executed
by the Company.

2. OWNERSHIP OF INVENTIONS

      "Invention" as used in this Agreement means any invention, discovery or
innovation with regard to biotechnology, genetic engineering or recombinant DNA
technology, whether or not patentable, made, conceived, or first actually
reduced to practice by Consultant, solely or jointly with others, in the course
of, in connection with, or as a result of, his service as a consultant to the
Company, including any art, method, process, machine, manufacture, design or
composition of matter, or any improvement thereof, or any variety of plant or
microorganism.

      Each Invention made, conceived or first actually reduced to practice by
Consultant, whether by himself or jointly with others, during the term of this
Agreement and each Invention made, conceived or first actually reduced to
practice by Consultant, whether by himself or jointly with others, within one
year after the termination of this Agreement which relates in any way to work he
performed for the Company during the term of this Agreement, shall be promptly
disclosed in writing to the President of the Company (or such other officer of
the Company as the President may designate). Such report shall be sufficiently
complete in technical detail and appropriately illustrated by sketch or diagram
to convey to one skilled in the art to which the Invention pertains, a clear
understanding of the nature, purpose, operation, and, to the extent known, the
physical, chemical, biological or electrical characteristics of the Invention.
Each Invention, as herein defined, shall be the sole and exclusive property of
the Company.

      Consultant agrees to execute an assignment to the Company or its nominee
of his entire right, title and interest in and to any Invention, without
compensation beyond that provided in this Agreement. Consultant further agrees,
upon the request of the Company and at its expense, that he will execute any
other instrument and document necessary or desirable in applying for and
obtaining patents in the United States and in any foreign country with respect
to any Invention. Consultant further agrees, whether or not he is then a
consultant of the Company, to cooperate to the extent and in the manner
reasonably requested by the Company in the prosecution or defense of any claim
involving a patent covering any Invention or any litigation or other claim or
proceeding involving any Invention covered by this Agreement, but all expenses
thereof shall be paid by the Company.



3. CONFIDENTIAL INFORMATION

      "Confidential Information," as used in this Agreement, means information
of the Company which is proprietary or confidential to it and includes
proprietary or confidential information as to any Invention, formula, apparatus,
equipment, trade secrets, research, report, technical data, as well as costs,
users or purchasers of the Company's services, research or products, or other
proprietary or confidential matters possessed, owned or used by the Company that
may be communicated to, acquired by, or learned of by Consultant in the course
of, in connection with, or as a result of, his consulting with the Company.
Confidential Information does not include (i) information which is or later
becomes publicly known under circumstances involving no breach of this
Agreement; (ii) information already known to Consultant (other than by previous
disclosure to him by the Company or through services performed by him for the
Company) as evidenced by his written records at the time of its receipt from the
Company; and (iii) information lawfully and in good faith made available to
Consultant without restriction on disclosure by a third party; provided,
however, that Confidential Information disclosed to Consultant by the Company
shall not be deemed to be available to the public or in his prior possession
merely because it is embraced by more general information available to the
public or in his prior possession.

      Consultant agrees that he will not (except as required in the course of
consulting with the Company), both during the term of this Agreement and
thereafter, communicate or divulge to, or use for his own benefit or the benefit
of any other person, firm or organization, any Confidential Information.

      Records, files, memoranda, reports, price lists, customer lists, drawings,
plans, sketches and documents and the like, relating to the business of the
Company, which Consultant shall use or prepare or come into contact with in the
course of, in connection with or as a result of, consulting with the Company,
shall remain the Company's sole and exclusive property and shall be subject to
the obligations of this Section 3.

      The obligations assumed by Consultant under this Section 3 are subject to
the understanding that Consultant is a member of the faculty of the
Massachusetts Institute of Technology ("MIT") and that, as such, he must fulfill
certain obligations to MIT, including, among other things, teaching, directing
laboratory operations and publishing. As a member of the faculty of MIT,
Consultant is also responsible for ensuring that any consulting agreement he
enters into is not in conflict with the patent and copyright policy of MIT or in
conflict with other MIT commitments. In the event of any conflict between this
Agreement and the conditions of Consultant's appointment to the faculty of MIT,
the latter will prevail.

      Publications by Consultant in academic or other journals, magazines or the
like are covered by the restrictions imposed by this Section 3 to the following
extent:

      Consultant agrees to submit each proposed publication which contains
information regarding Inventions to the President of the Company (or such other
officer or consultant to the Company as the President may designate) for advance
review to determine whether or not such publication contains Confidential
Information. Consultant may proceed with publication unless he is notified
within fourteen days of such submission by the Company that such publication
contains Confidential Information which the Company desires to keep
confidential, which notice shall specify with particularity such Confidential
Information. Consultant may thereafter proceed with publication only if he is
able to delete the



Confidential Information specified by the Company. Consultant may publish the
results of his and his laboratory's research which does not contain information
regarding Inventions without advance review by the Company.

4. MISCELLANEOUS

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

      All notices, requests, demands and other communications to be given
pursuant to this Agreement shall be in writing and shall be deemed to have been
duly given if delivered by hand or mailed by registered or certified mail,
return receipt requested, postage prepaid, as follows:

      If to the Company, to:
            Repligen Corporation
            50 Staniford Street
            Boston, Massachusetts 02114
            Attention: President

      If to Consultant, to:
            Dr. Paul R. Schimmel
            44 Sanderson Road
            Lexington, Massachusetts 02173

or such other address as either party hereto shall have designated by notice in
writing to the other party.

      At any time this Agreement may be amended, supplemented or otherwise
modified, but only by an instrument in writing signed by the parties hereto.

      Consultant is an independent contractor under this Agreement. He is not an
employee of the Company and will not be entitled to participate in, or receive
any benefit or right as an employee under any employee benefit and welfare plan,
including, without limitation, employee insurance, pension, savings and security
plans, as a result of his entering into this Agreement.

      This Agreement and the legal relations among the parties hereto shall be
governed by and construed in accordance with the laws of the Commonwealth of
Massachusetts.

      In case any provision hereof shall, for any reason, be held to be invalid
or unenforceable in any respect, such invalidity or unenforceability shall not
affect any other provision hereof, and this Agreement shall be construed as if
such invalid or unenforceable provision had not been included herein. If any
provision hereof shall, for any reason, be held by a court to be excessively
broad as to duration, geographical scope, activity or subject, it shall be
construed by limiting and reducing it to make it enforceable to the extent
compatible with applicable law as then in effect.

      This Agreement shall inure to the benefit of and be binding upon the
parties hereto and their respective heirs, successors, assigns and personal
representatives.



      Neither this Agreement nor any rights hereunder shall be assignable by any
party hereto without the prior written consents of the other parties.

IN WITNESS WHEREOF, the undersigned have duly executed and delivered this
Agreement as of the date first above written.

                                  REPLIGEN CORPORATION
                                  /s/ William M. Jackson
                                  ----------------------

                                  /s/ Paul R. Schimmel
                                  --------------------
                                  Dr. Paul Schimmel