Document:

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                                                                   Exhibit 10.31

                        DATED this 16th day of March 1997

                                     BETWEEN

                               BIOTRANSPLANT INC.
                                     ("BTI")

                                      -and-

                            CASTELLA RESEARCH PTY LTD
                                  ("Castella")

                                      -and-

                             SECURE SCIENCES PTY LTD
                                   ("Secure")

                                      -and-

                           STEM CELL SCIENCES PTY LTD
                                 ("the Company")

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                AGREEMENT TO FURTHER VARY SHAREHOLDERS' AGREEMENT

-------------------------------------------------------------------------------

                                 HOLDING REDLICH
                             LAWYERS AND CONSULTANTS

350 Williams Street                                     Level 12, Chifley Tower
Melbourne VIC 3000                                      2 Chifley Square
                                                        Sydney NSW 2000

Tel (03) 93219999                                       Tel (02) 234 4444
Fax (03) 93219900                                       Fax (02) 234 4400

Ref: CLSCS113.27

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AGREEMENT TO FURTHER VARY SHAREHOLDERS' AGREEMENT dated the 16 day of March 1997

BETWEEN: BIOTRANSPLANT INCORPORATED a corporation organised and existing under
         the laws of the State of Delaware and having its principal office 13
         Pipp Street, Building 96, Navy Yard, Charlestown, MA, United States of
         America

                                                                         ("BTI")

AND:     CASTELLA RESEARCH PTY LTD (ACN 006 125 364) of 587 Whitehorse Road,
         Mont Albert, Victoria, Australia in its own capacity and as trustee of
         the M.R. Brandon Family Trust

                                                                    ("CASTELLA")

AND:     SECURE SCIENCES PTY LTD (ACN 064 139 948) of Level 10, 420 St. Kilda
         Road, Melbourne, Victoria, Australia in its own capacity and as
         trustee of the Secure Sciences Unit Trust

                                                                      ("SECURE")

AND:     STEM CELL SCIENCES PTY LTD (ACN 063 293 130) of Level 10, 420 St.
         Kilda Road, Melbourne, Victoria, Australia

                                                                 ("THE COMPANY")

 RECITALS

A.       By a Shareholders' Agreement dated 5 April, 1994 between BTI, Castella,
         Secure and the Company (the "Shareholders' Agreement") the Shareholders
         recorded their agreement as to how the Company would be owned,
         controlled and funded by them.

B.       The Shareholders' Agreement was varied by Variations of the
         Shareholders' Agreement made on 2 February 1996 and 20 December 1996
         (the "Second Vaiaition Agreement").

C.       Pursuant to the Second Variation Agreement:

         (a) BIT was issued with an option to subscribe for 300 "A" Shares in
         the capital of the Company for a total consideration of US
         $2,071,343.75 at any time on or before 31 December, 1996;

         (b) Castella was issued with an option to subscribe for 150 "B" SHARES
         in the capital of the Company for a total consideration of $150.00, at
         any time on or before 31 December, 1996; and

         (c) Secure was issued with an option to subscribe for 550 "B" Shares in
         the capital of the Company for a total consideration of $550.00 at any
         time on or before 31 December, 1996

                                       2
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D.       None of BTI, Castella and Secure have exercised the options issued to
         them pursuant to the Second Variation Agreement.

E.       BTI has agreed to provide an amount of equity capital to the Company.

F.       In line with the intent of the Shareholders' Agreement that on the
         provision by BTI of equity capital to the Company such shares in the
         Company would be issued to maintain the shareholdings of BTI, Castella
         and Secure in the Company in the ratios set out in Recital J, the
         Shareholders have agreed to cause the Company to allot to BTI a certain
         addition number of "A" shares in the capital of the Company at a
         premium and to allot to Castella and Secure certain additional "B"
         Shares in the capital of the Company at par.

G.       The Shareholders and the Company have also agreed that the Company will
         allot to BTI, Castella and Secure fresh options on the terms set out in
         this Agreement.

H.       Clause 18.5 of the Shareholders' Agreement provides that the
         Shareholders' Agreement may not be modified, amended, added to or
         otherwise varied except by a document in writing signed by each of the
         parties or signed on behalf of each party by a director under hand.

I.       The parties wish by this Agreement to record the matters set out in
         Recitals E to G and to vary the Shareholders' Agreement to the extent
         necessary to take account of those matters.

IT IS AGREED

1.       DEFINITIONS AND INTERPRETATION
         ------------------------------

1.1      DEFINITIONS

         In this Agreement (including in the Recitals), unless the contrary
         intention appears, each defined word and expression has the meaning
         assigned to that word or expression in the Shareholders' Agreement.

1.2      INTERPRETATION

         Clauses 1.3 and 1.4 of the Shareholders' Agreement are incorporated in
         and form part of this Agreement as if each referenced to "this
         Agreement" in those clauses were a reference to this Agreement to vary
         the Shareholders' Agreements.

1.3      RECITALS

         The parties acknowledge and agree that the Recitals are true and
         correct and accurately reflect the circumstances in which this
         Agreement was entered into.

                                       3
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2.       ISSUE OF SHARES
         ---------------

2.1      ISSUE OF SHARES TO BTI

         On the date of this Agreement BTI must subscribe for, and be issued
         with 300 "A" Shares in the capital of the Company issued at a price of
         $2,862.75 per share (being $1.00 par and $2,862.75 premium per share)
         for a total consideration of $859,125.00.

2.2      Issue of Shares to Castella

         On the date of this Agreement Castella must subscribe for and be issued
         with 150 "B" Shares in the capital of the Company issued at the par
         price of $1.00 per share for a total consideration of $150.00 payable
         on the date of this Agreement.

2.3      ISSUE OF SHARES TO SECURE

         On the date of this Agreement Secure must subscribe for and be issued
         with 550 "B" Shares in the capital of the Company issue at the par
         price of $1.00 per share for a total consideration of $550.00 payable
         on the date of this Agreement.

3.       ISSUE OF OPTIONS
         ----------------

3.1      Issue of Options to BTI

         (a)      On the date of this Agreement, the Company must issue to BTI
                  an option (the Option Terms attaching) to subscribe for, fully
                  pay up and be issued with a further 300 "A" Shares in the
                  capital of the Company for a total consideration of US
                  $1,405,951.50 at any time on or before 31 December, 1997 ("the
                  option").

         (b)      If BTI exercises the option the Company will issue BTI 300 "A"
                  Shares in the capital of the Company at a price per share of
                  A$1.00 (being the par value) plus a premium per share
                  calculated in A$ as at the date of the exercise of the option.

3.2      ISSUE OF OPTION TO CASTELLA

         On the date of this Agreement, the Company must issue to Castella an
         option (with the Option Terms attaching) to subscribe for, fully pay up
         and be issued with a further 150 "B" Shares in the capital of the
         Company issued at a price of $1.00 per share for a total consideration
         of $150.00 at any time on or before 31 December, 1997.

3.3      Issue of Option to Secure

         On the date of this Agreement, the Company must issue to Secure an
         option (the Options Terms attaching) to subscribe for, fully pay up and
         be issued with a further 550 "B" Shares in the capital of the Company
         issued at a price of $1.00 per share for a total consideration of
         $550.00 at any time on or before 31 December, 1997.

                                       4
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4.       VARIATION OF SHAREHOLDERS' AGREEMENT
         ------------------------------------

4.1      VARIATION

         In consideration of the mutual agreements made by each party under this
         Agreement, the parties agree, pursuant to cause 18.5 of the
         Shareholders' Agreement, to vary clause 2.5 of the Shareholders'
         Agreement to the extent necessary to give effect to the provisions of
         Clauses 2 and 3 of this Agreement.

4.2      CONFIRMATION OF SHAREHOLDERS' AGREEMENT

         The parties confirm that the terms and conditions of the Shareholders'
         Agreement (as varied by this Agreement) remain in full force and
         effect.

                                       5

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SIGNED AS AN AGREEMENT on the date first appearing

SIGNED by BIOTRANSPLANT INC.        )

by its director ELLIOT LEBOWITZ     )                       /s/ ELLIOT LEBOWITZ
                                                            -------------------
in the presence of:                 )

-------------------------------------
(Witness)

SIGNED by CASTELLA RESEARCH         )

PTY LTD by its director MAL BRANDON )                       /s/ MAL BRANDON
                                                            -------------------
in the presence of:                 )

-------------------------------------
(Witness)

SIGNED by SECURE SCIENCES PTY LTD   )

by its director PETER MOUNTFORD     )                       /s/ PETER MOUNTFORD
                                                            -------------------
in the presence of:                 )

-------------------------------------
(Witness)

SIGNED by STEM CELL SCIENCES        )

PTY LTD by its director MEL BRANDON )                       /s/ MEL BRANDON
                                                            -------------------
in the presence of:                 )

-------------------------------------
(Witness)

                                       6<PAGE>

                                                                    EXHIBIT 10.1

                                 EMC CORPORATION

               1985 STOCK OPTION PLAN, as amended January 17, 2001

1.       PURPOSE.
         -------

         The purpose of the EMC Corporation 1985 Stock Option Plan is to enable
EMC Corporation to provide a special incentive to a limited number of key
employees of the Company and its Subsidiaries, if any, who are in a position to
have a significant effect upon the Company's business and earnings. In order to
accomplish this purpose, the Plan authorizes the grant to such key employees of
options to purchase Common Stock of the Company. Increased ownership of Common
Stock will provide such key employees with an additional incentive to take into
account the long-term interests of the Company.

2.       DEFINITIONS.
         -----------

         As used herein, the following words or terms have the meanings set
forth below. The masculine gender is used throughout the Plan but is intended to
apply to members of both sexes.

         2.1 "Board of Directors" means the Board of Directors of the Company.

         2.2 "Code" means the Internal Revenue Code of 1986, as amended from
time to time, or any successor statute.

         2.3 "Committee" means the Committee appointed by the Board of Directors
to administer the Plan or the Board of Directors as a whole if no appointment is
made.

         2.4 "Common Stock" means the Common Stock of the Company.

         2.5 "Company" means EMC Corporation, a corporation established under
the laws of The Commonwealth of Massachusetts.

         2.6 "Fair Market Value" in the case of a share of Common Stock on a
particular day, means the fair market value as determined from time to time by
the Board of Directors or, where appropriate, by the Committee, taking into
account all information which the Board of Directors, or the Committee,
considers relevant.

         2.7 "Incentive Stock Option" means a stock option that satisfies the
requirements of Section 422 of the Code.

         2.8 "Participant" means an individual holding a stock option or stock
options granted to him under the Plan.

         2.9 "Plan" means the EMC Corporation 1985 Stock Option Plan set forth
herein.

         2.10 "Subsidiary" or "Subsidiaries" means a corporation or corporations
in which the Company owns, directly or indirectly, stock possessing 50 percent
or more of the total combined voting power of all classes of stock.

         2.11 "Ten Percent Stockholder" means any person who, at the time an
option is granted, owns or is deemed to own stock (as determined in accordance
with Sections 422 and 424 of the Code) possessing more than ten percent (10%) of
the total combined voting power of all classes of stock of the Company or its
parent or a subsidiary.

                                   Page 1 of 7

<PAGE>

3.       ADMINISTRATION.
         --------------

         3.1 The Plan shall be administered by the Committee and, to the extent
provided herein, the Board of Directors. A majority of the members of the
Committee shall constitute a quorum, and all determinations of the Committee
shall be made by a majority of its members. Any determination of the Committee
under the Plan may be made without notice or meeting of the Committee by a
writing signed by a majority of the Committee members.

         3.2 Subject to the provisions set forth herein, each of the Committee
and the Board of Directors shall have full authority to determine the provisions
of options to be granted under the Plan. Subject to the provisions set forth
herein, the Committee shall have full authority to interpret the terms of the
Plan and of options granted under the Plan, to adopt, amend and rescind rules
and guidelines for the administration of the Plan and for its own acts and
proceedings and to decide all questions and settle all controversies and
disputes which may arise in connection with the Plan; PROVIDED, HOWEVER, that
any change to the terms of an option granted hereunder shall be approved by the
Board of Directors to the extent such change would be deemed to be a new option
grant or such terms relate to a subsequent transaction that would not be exempt
from Section 16(b) of the Securities Exchange Act of 1934 in the absence of such
approval.

         3.3 The decision of the Committee or the Board of Directors, as
applicable, on any matter as to which the Committee or the Board of Directors,
as applicable, is given authority under subsection 3.2 shall be final and
binding on all persons concerned.

         3.4 Nothing in the Plan shall be deemed to give any officer or
employee, or his legal representatives or assigns, any right to participate in
the Plan, except to such extent, if any, as the Committee or the Board, as
applicable, may have determined or approved pursuant to the provisions of the
Plan.

4.       SHARES SUBJECT TO THE PLAN.
         --------------------------

         4.1 The maximum number of shares of Common Stock that may be delivered
upon the exercise of options granted under the Plan shall be 288,000,000,
subject to adjustment in accordance with the provisions of Section 8.

         4.2 If any option granted under the Plan terminates without having been
exercised in full (including an option which terminates by agreement between the
Company and the Participant), the number of shares of Common Stock as to which
such option has not been exercised prior to termination shall be available for
future grants within the limits set forth in subsection 4.1.

         4.3 Shares of Common Stock delivered upon the exercise of options shall
consist of shares of authorized and unissued Common Stock, except that the Board
of Directors may from time to time in its discretion determine in any case the
shares to be so delivered shall consist of shares of authorized and issued
Common Stock reacquired by the Company and held in its Treasury. No fractional
shares of Common Stock shall be delivered upon the exercise of an option.

5.       ELIGIBILITY FOR OPTIONS.
         -----------------------

         Employees eligible to receive options under the Plan shall be those key
employees of the Company and its Subsidiaries, if any, who, in the opinion of
the Committee, are in a position to have a significant effect upon the Company's
business and earnings. Members of the Board of Directors of the Company or a
Subsidiary who are not employed as regular salaried officers or employees of the
Company or a Subsidiary may not participate in the Plan.

                                   Page 2 of 7

<PAGE>

6.       GRANT OF OPTIONS.
         ----------------

         6.1 From time to time while the Plan is in effect, each of the
Committee and the Board of Directors may, in its absolute discretion, select
from among the persons eligible to receive options (including persons to whom
options were previously granted) those persons to whom options are to be
granted.

         6.2 Each of the Committee and the Board of Directors shall, in its
absolute discretion, determine the number of shares of Common Stock to be
subject to each option granted by it under the Plan.

         6.3 No Incentive Stock Option may be granted under the Plan after May
16, 1995, but options theretofore granted may extend beyond that date.

7.       PROVISIONS OF OPTIONS.
         ---------------------

         7.1 INCENTIVE STOCK OPTIONS OR OTHER OPTIONS. Options granted under the
Plan may be either Incentive Stock Options or options which do not qualify as
Incentive Stock Options, as the Committee or the Board of Directors shall
determine at the time of each grant of options hereunder.

         7.2 STOCK OPTION CERTIFICATES OR AGREEMENTS. Options granted under the
Plan shall be evidenced by certificates or agreements in such form as the
Committee shall from time to time approve. Such certificates or agreements shall
comply with the terms and conditions of the Plan and may contain such other
provisions not inconsistent with the terms and conditions of the Plan as the
Committee shall deem advisable. In the case of options intended to qualify as
Incentive Stock Options, the certificates or agreements shall contain such
provisions relating to exercise and other matters as are required of incentive
stock options under the Code.

         7.3 TERMS AND CONDITIONS. All options granted under the Plan shall be
subject to the following terms and conditions to the extent applicable and to
such other terms and conditions not inconsistent therewith as the Committee or
the Board of Directors shall determine:

                  7.3.1 Exercise Price. The exercise price per share of Common
         Stock with respect to each option shall be as determined by the
         Committee but in the case of an Incentive Stock Option not less than
         100% (110% in the case of an Incentive Stock Option granted to a Ten
         Percent Stockholder) of the Fair Market Value per share at the time the
         option is granted. In the case of an option which does not qualify as
         an Incentive Stock Option, the exercise price per share of Common Stock
         shall be not less than par value. However, for those employees subject
         to Section 16 of the Securities Exchange Act of 1934, the per share
         exercise price for an option which does not qualify as an Incentive
         Stock Option shall not be less than 50% of the Fair Market Value at the
         time the option is granted.

                  7.3.2 VALUE OF SHARES OF COMMON STOCK SUBJECT TO INCENTIVE
         STOCK OPTIONS. Each eligible employee may be granted Incentive Stock
         Options only to the extent that, in the aggregate under this Plan and
         all incentive stock option plans of the Company and any related
         corporation, such Incentive Stock Options do not become exercisable for
         the first time by such employee during any calendar year in a manner
         which would entitle the employee to purchase more than $100,000 in fair
         market value (determined at the time the Incentive Stock Options were
         granted) of Common Stock in that year. Any options granted to any
         employee in excess of such amount will be granted as Non-Qualified
         Options.

                  7.3.3 PERIOD OF OPTIONS. An option shall be exercisable during
         such period of time as the Committee or the Board of Directors may
         specify (subject to subsection 7.4 below), but in the case of an
         Incentive Stock Option not after the expiration of ten years (five
         years in the case of an Incentive Stock Option granted to a Ten Percent
         Stockholder) from the date the option is granted.

                                   Page 3 of 7

<PAGE>

                  7.3.4  EXERCISE OF OPTIONS.
                         -------------------

                           7.3.4.1 Each option shall be made exercisable at such
                  time or times as the Committee or the Board of Directors shall
                  determine. In the case of an option made exercisable in
                  installments, the Committee or the Board of Directors may
                  later determine to accelerate the time at which one or more of
                  such installments may be exercised.

                           7.3.4.2 Any exercise of an option shall be in writing
                  signed by the proper person and delivered or mailed to the
                  General Counsel of the Company, accompanied by an option
                  exercise notice and payment in full for the number of shares
                  in respect to which the option is exercised.

                           7.3.4.3 In the event an option is exercised by the
                  executor or administrator of a deceased Participant, or by the
                  person or persons to whom the option has been transferred by
                  the Participant's will or the applicable laws of descent and
                  distribution, the Company shall be under no obligation to
                  deliver stock thereunder until the Company is satisfied that
                  the person or persons exercising the option is or are the duly
                  appointed executor or administrator of the deceased
                  Participant or the person or persons to whom the option has
                  been transferred by the Participant's will or by the
                  applicable laws of descent and distribution.

                           7.3.4.4 The Committee or the Board of Directors may
                  at the time of grant condition the exercise of an option upon
                  agreement by the Participant to subject the Common Stock to
                  any restrictions on transfer or repurchase rights in effect on
                  the date of exercise, upon representations of continued
                  employment and upon other terms not inconsistent with this
                  Plan. Any such conditions shall be set forth in the option
                  certificate or other document evidencing the option.

                           7.3.4.5 In the case of an option that is not an
                  Incentive Stock Option, the Committee shall have the right to
                  require that the individual exercising the option to remit to
                  the Company an amount sufficient to satisfy any federal,
                  state, or local withholding tax requirements (or makes other
                  arrangements satisfactory to the Company with regard to such
                  taxes) prior to the delivery of any Common Stock pursuant to
                  the exercise of the option. In the case of an Incentive Stock
                  Option, if at the time the Incentive Stock Option is exercised
                  the Committee determines that under applicable law and
                  regulations the Company could be liable for the withholding of
                  any federal or state tax with respect to a disposition of the
                  Common Stock received upon exercise, the Committee may require
                  as a condition of exercise that the individual exercising the
                  Incentive Stock Option agree (i) to inform the Company
                  promptly of any disposition (within the meaning of Section 422
                  (a) (1) of the Code and the regulations thereunder) of Common
                  Stock received upon exercise, and (ii) to give such security
                  as the Committee deems adequate to meet the potential
                  liability of the Company for the withholding of tax, and to
                  augment such security from time to time in any amount
                  reasonably deemed necessary by the Committee to preserve the
                  adequacy of such security.

                           7.3.4.6 In the case of an option that is exercised by
                  an individual that is subject to taxation in a foreign
                  jurisdiction, the Committee shall have the right to require
                  the individual exercising the option to remit to the Company
                  an amount sufficient to satisfy any federal or withholding
                  requirement of that foreign jurisdiction (or make other
                  arrangements satisfactory to the Company with regard to such
                  taxes prior to the delivery of any Common Stock pursuant to
                  the exercise of the option).

                  7.3.5 PAYMENT FOR AND DELIVERY OF STOCK. The shares of stock
         purchased on any exercise of an option granted hereunder shall be paid
         for in full in cash or, if permitted by the terms of the option, in
         shares of unrestricted Common Stock at the time of such exercise or, if
         so permitted, a

                                   Page 4 of 7

<PAGE>

         combination of such cash and Common Stock. A Participant shall not have
         the rights of a stockholder with respect to awards under the Plan
         except as to stock actually issued to him.

                  7.3.6 LISTING OF STOCK, WITHHOLDING AND OTHER LEGAL
         REQUIREMENTS. The Company shall not be obligated to deliver any stock
         until all federal and state laws and regulations which the Company may
         deem applicable have been complied with, nor, in the event the
         outstanding Common Stock is at the time listed upon any stock exchange,
         until the stock to be delivered has been listed or authorized to be
         added to the list upon official notice of issuance to such exchange. In
         addition, if the shares of stock subject to any option have not been
         registered in accordance with the Securities Act of 1933, as amended,
         the Company may require the person or persons who wishes or wish to
         exercise such option to make such representation or agreement with
         respect to the sale of stock acquired on exercise of the option as will
         be sufficient, in the opinion of the Company's counsel, to avoid
         violation of said Act, and may also require that the certificates
         evidencing said stock bear an appropriate restrictive legend.

                  7.3.7 NON-TRANSFERABILITY OF OPTIONS. No option may be
         transferred by the Participant otherwise than by will, by the laws of
         descent and distribution or pursuant to a qualified domestic relations
         order, and during the Participant's lifetime the option may be
         exercised only by him or her; PROVIDED, HOWEVER, that the Board of
         Directors or the Committee, as applicable, in its discretion, may allow
         for transferability of non-qualified stock options by the Participant
         to "Immediate Family Members". Immediate Family Members means children,
         grandchildren, spouse or common law spouse, siblings or parents of the
         Participant or to bona fide trusts, partnerships or other entities
         controlled by and of which the beneficiaries are Immediate Family
         Members of the Participant. Any option grants that are transferable are
         further conditioned on the Participant and Immediate Family Members
         agreeing to abide by the Company's then current stock option transfer
         guidelines.

                  7.3.8 DEATH. If a Participant dies at a time when he is
         entitled to exercise an Incentive Stock Option, then at any time or
         times within three years after his death such Incentive Stock Option
         may be exercised, as to all or any of the shares which the Participant
         was entitled to purchase thereunder immediately prior to his death, by
         his executor or administrator or the person or persons to whom the
         Incentive Stock Option is transferred by will or the applicable laws of
         descent and distribution, and except as so exercised such Incentive
         Stock Option shall expire at the end of such three-year period. In no
         event, however, may any Incentive Stock Option granted under the Plan
         be exercised after the expiration of ten years (five years in the case
         of an Incentive Stock Option granted to a Ten Percent Stockholder) from
         the date the Incentive Stock Option was granted.

                  7.3.9 TERMINATION OF EMPLOYMENT. If the employment of a
         Participant terminates for any reason other than his death, all options
         held by the Participant shall thereupon expire on the date of
         termination unless the option by its terms, or the Committee or the
         Board of Directors by resolution, shall allow the Participant to
         exercise any or all of the options held by him after termination. In
         the case of an Incentive Stock Option, the Incentive Stock Option shall
         in any event expire at the end of three months after such termination
         of employment, or after the expiration of ten years (five years in the
         case of an Incentive Stock Option granted to a Ten Percent Stockholder)
         from the date the Incentive Stock Option was granted, whichever occurs
         first. If the Committee or the Board of Directors so decides, an option
         may provide that a leave of absence granted by the Company or
         Subsidiary is not a termination of employment for the purpose of this
         subsection 7.3.9, and in the absence of such a provision the Committee
         may in any particular case determine that such a leave of absence is
         not a termination of employment for such purpose. The Committee shall
         also determine all other matters relating to continuous employment.

                  7.3.10 CANCELLATION AND RESCISSION OF OPTIONS. The following
         provisions of this Section 7.3.10 shall apply to options granted on or
         after July 1, 1998 to (i) Participants who are classified by the
         Company or a Subsidiary as an executive officer, senior officer, or
         officer (collectively, an "Officer") of the Company or a Subsidiary;
         and (ii) certain other Participants designated by the

                                   Page 5 of 7

<PAGE>

         Committee or the Board of Directors to be subject to the terms of this
         Section 7.3.10 (such designated Participants together with Officers
         referred to collectively as "Senior Participants"). The Committee or
         the Board of Directors may cancel, rescind, suspend or otherwise limit
         or restrict any unexpired option at any time if the Senior Participant
         engages in "Detrimental Activity" (as defined below). Furthermore, in
         the event a Senior Participant engages in Detrimental Activity at any
         time prior to or during the six months after any exercise of an option,
         such exercise may be rescinded until the later of (i) two years after
         such exercise or (ii) two years after such Detrimental Activity. Upon
         such rescission, the Company at its sole option may require the Senior
         Participant to (i) deliver and transfer to the Company the shares of
         Common Stock received by the Senior Participant upon such exercise,
         (ii) pay to the Company an amount equal to any realized gain received
         by the Senior Participant from such exercise, or (iii) pay to the
         Company an amount equal to the market price (as of the exercise date)
         of the Common Stock acquired upon such exercise minus the respective
         exercise price. The Company shall be entitled to set-off any such
         amount owed to the Company against any amount owed to the Senior
         Participant by the Company. As used in this subsection 7.3.10,
         "Detrimental Activity"shall include: (i) the failure to comply with the
         terms of the Plan or certificate or agreement evidencing the option;
         (ii) the failure to comply with any term set forth in the Company's Key
         Employee Agreement (irrespective of whether the Senior Participant is a
         party to the Key Employee Agreement); (iii) any activity that results
         in termination of the Senior Participant's employment for cause; (iv) a
         violation of any rule, policy, procedure or guideline of the Company;
         or (v) the Senior Participant being convicted of, or entering a guilty
         plea with respect to a crime whether or not connected with the Company.
         Further, if the Company commences an action against such Senior
         Participant (by way of claim or counterclaim and including declaratory
         claims), in which it is preliminarily or finally determined that such
         Senior Participant engaged in Detrimental Activity or otherwise
         violated this Section 7.3.10, the Senior Participant shall reimburse
         the Company for all costs and fees incurred in such action, including
         but not limited to, the Company's reasonable attorneys' fees.

                  7.3.11 JURISDICTION AND GOVERNING LAW. The parties submit to
         the exclusive jurisdiction and venue of the federal or state courts of
         the Commonwealth of Massachusetts, County of Middlesex, to resolve
         issues that may arise out of or relate to the Plan or the same subject
         matter. The Plan shall be governed by the laws of the Commonwealth of
         Massachusetts, excluding its conflicts or choice of law rules or
         principles that might otherwise refer construction or interpretation of
         this Plan to the substantive law of another jurisdiction.

         7.4 AUTHORITY OF THE COMMITTEE. The Committee shall have the authority,
either generally or in particular instances, to waive compliance by a
Participant with any obligation to be performed by him under an option and to
waive any condition or provision of an option, except that the Committee may not
(i) increase the total number of shares covered by any Incentive Stock Option
(except in accordance with Section 8), (ii) reduce the option price per share of
any Incentive Stock Option (except in accordance with Section 8) or (iii) extend
the term of any Incentive Stock Option to more than ten years, subject, however,
to the provisions of Section 10.

8.       CHANGES IN STOCK.
         ----------------

         In the event of a stock dividend, stock split or other change in
corporate structure or capitalization affecting the Common Stock that becomes
effective after the adoption of the Plan by the Board of Directors, the
Committee shall make appropriate adjustments in (i) the number and kind of
shares of stock on which options may thereafter be granted hereunder, (ii) the
number and kind of shares of stock remaining subject to each option outstanding
at the time of such change and (iii) the option price. The Committee's
determination shall be binding on all persons concerned. Subject to any required
action by the stockholders, if the Company shall be the surviving corporation in
any merger or consolidation (other than a merger or consolidation in which the
Company survives but in which a majority of its outstanding shares are converted
into securities of another corporation or are exchanged for other
consideration), any option granted hereunder shall pertain and apply to the
securities which a holder of the number of shares of stock of the Company then
subject to the option would have been entitled to receive, but a dissolution or

                                   Page 6 of 7

<PAGE>

liquidation of the Company or a merger or consolidation in which the Company is
not the surviving corporation or in which a majority of its outstanding shares
are so converted or exchanged shall cause every option hereunder to terminate;
provided that if any such dissolution, liquidation, merger or consolidation is
contemplated, the Company shall either arrange for any corporation succeeding to
the business and assets of the Company to issue to the Participants replacement
options (which, in the case of Incentive Stock Options, satisfy, in the
determination of the Committee, the requirements of Section 424 of the Code) on
such corporation's stock which will to the extent possible preserve the value of
the outstanding options or shall make the outstanding options fully exercisable
at least 20 days before the effective date of any such dissolution, liquidation,
merger or consolidation. The existence of the Plan shall not prevent any such
change or other transaction and no Participant thereunder shall have any right
except as herein expressly set forth.

9.       EMPLOYMENT RIGHTS.
         -----------------

         Neither the adoption of the Plan nor any grant of options confers upon
any employee of the Company or a Subsidiary any right to continued employment
with the Company or a Subsidiary, as the case may be, nor does it interfere in
any way with the right of the Company or a Subsidiary to terminate the
employment of any of its employees at any time.

10.      DISCONTINUANCE, CANCELLATION, AMENDMENT AND TERMINATION.
         -------------------------------------------------------

         The Committee or the Board of Directors may at any time discontinue
granting options under the Plan and, with the consent of the Participant, may at
any time cancel an existing option in whole or in part and grant another option
to the Participant for such number of shares as the Committee or the Board of
Directors specifies. The Board of Directors may at any time or times amend the
Plan for the purpose of satisfying the requirements of any changes in applicable
laws or regulations or for any other purpose which may at the time be permitted
by law or may at any time terminate the Plan as to any further grants of
options, provided that no such amendment shall without the approval of the
stockholders of the Company (a) increase the maximum number of shares available
under the Plan, (b) change the group of employees eligible to receive options
under the Plan, (c) reduce the exercise price of outstanding incentive options
or reduce the price at which incentive options may be granted, (d) extend the
time within which options may be granted, (e) alter the Plan in such a way that
incentive options granted or to be granted hereunder would not be considered
incentive stock options under Section 422 of the Code, or (f) amend the
provisions of this Section 10, and no such amendment shall adversely affect the
rights of any employee (without his consent) under any option previously
granted.

11.      EFFECTIVE DATE.
         --------------

         The Plan shall become effective upon its adoption by the Board of
Directors, and options may be granted under the Plan from and after the date of
such adoption; provided, however, that if prior to May 16, 1986 the stockholders
of the Company have not approved the Plan, the Plan shall terminate to the
extent that it relates to the issuance of Incentive Stock Options and all
Incentive Stock Options theretofore granted shall terminate and cease to be of
any force or effect. No Incentive Stock Option granted hereunder shall be
exercisable unless and until the Plan has been so approved.

                                   Page 7 of 7

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