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                                                                EXHIBIT 4.2

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, OR ANY APPLICABLE STATE SECURITIES LAWS, AND MAY NOT BE SOLD OR
TRANSFERRED UNLESS SUCH SALE OR TRANSFER IS IN ACCORDANCE WITH THE
REGISTRATION REQUIREMENTS OF SUCH ACT AND APPLICABLE LAWS OR SOME OTHER
EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF SUCH ACT AND APPLICABLE LAWS
IS AVAILABLE WITH RESPECT THERETO.

                          COMMON STOCK PURCHASE WARRANT

Warrant No. C-___                                         Number of Shares ___

                                 METABOLIX, INC.

                          COMMON STOCK PURCHASE WARRANT

                   Void Unless Exercised before _____________

     This Warrant is one of the Common Stock Purchase Warrants (the "Warrants")
evidencing the right to purchase shares of Common Stock of the Company issued
pursuant to certain ___________ Stock and Warrant Purchase Agreement (each, an
"Agreement"), among the Company and the Investors named therein, a copy of which
is on file at the principal office of the Company and this Warrant shall be
subject to all of the provisions, including, without limitation, restrictions on
transfer, set forth in the Agreements.

     1. ISSUANCE. This Warrant is issued to _______________ by Metabolix,
Inc., a Delaware corporation (hereinafter with its successors called the
"Company").

     2. PURCHASE PRICE: NUMBER OF SHARES. Subject to the terms and conditions
hereinafter set forth, the registered holder of this Warrant (the "Holder"),
commencing on _______________ (the "Original Issue Date"), is entitled upon
surrender of this Warrant with the subscription form annexed hereto duly
executed, at the office of the Company, 21 Erie Street, Cambridge, Massachusetts
02139, or such other office as the Company shall notify the Holder of in
writing, to purchase from the Company at a price per share (the "Purchase
Price") of $________, fully paid and nonassessable shares of Common Stock, $.01
par value, of the Company (the "Common Stock"). Until such time as this Warrant
is exercised in full or expires, the Purchase Price and the securities issuable
upon exercise of this Warrant are subject to adjustment as hereinafter provided.

     3. PAYMENT OF PURCHASE PRICE. The Purchase Price may be paid (i) in cash or
by check, (ii) by the surrender by the Holder to the Company of any promissory
notes or other obligations issued by the Company, with all such notes and
obligations so surrendered being credited against the Purchase Price in an
amount equal to the principal amount thereof plus accrued interest to the date
of surrender, (iii) through delivery by the Holder to the Company of other
securities issued by the Company, with such securities

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being credited against the Purchase Price in an amount equal to the fair market
value thereof, as determined in good faith by the Board of Directors of the
Company (the "Board"), or (iv) by any combination of the foregoing.

The Board shall promptly respond in writing to an inquiry by the Holder as to
the fair market value of any securities the Holder may wish to deliver to the
Company pursuant to clause (iii) above.

     4. NET ISSUE ELECTION. The Holder may elect to receive, without the payment
by the Holder of any additional consideration, shares equal to the value of this
Warrant or any portion hereof by the surrender of this Warrant or such portion
to the Company, with the net issue election notice annexed hereto duly executed,
at the office of the Company. Thereupon, the Company shall issue to the Holder
such number of fully paid and nonassessable shares of Common Stock as is
computed using the following formula:

                                   X = Y (A-B)
                                       -------
                                        A

where

     X = the number of shares to be issued to the Holder pursuant to this
Section 4.

     Y = the number of shares covered by this Warrant in respect of which the
net issue election is made pursuant to this Section 4.

     A = the fair market value of one share of Common Stock, as determined in
good faith by the Board, as at the time the net issue election is made pursuant
to this Section 4.

     B = the Purchase Price in effect under this Warrant at the time the net
issue election is made pursuant to this Section 4.

The Board shall promptly respond in writing to an inquiry by the Holder as to
the fair market value of one share of Common Stock.

     5. PARTIAL EXERCISE. This Warrant may be exercised in part, and the Holder
shall be entitled to receive a new warrant, which shall be dated as of the date
of this Warrant, covering the number of shares in respect of which this Warrant
shall not have been exercised.

     6. ISSUANCE DATE. The person or persons in whose name or names any
certificate representing shares of Common Stock is issued hereunder shall be
deemed to have become the holder of record of the shares represented thereby as
at the close of business on the date this Warrant is exercised with respect to
such shares, whether or not the transfer books of the Company shall be closed.

     7. EXPIRATION DATE: AUTOMATIC EXERCISE. This Warrant shall expire at the
close of business on ____________, and shall be void thereafter.

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     8. RESERVED SHARES, VALID ISSUANCE. The Company covenants that it will at
all times from and after the Original Issue Date reserve and keep available such
number of its authorized shares of Common Stock, free from all preemptive or
similar rights therein, as will be sufficient to permit the exercise of this
Warrant in full. The Company further covenants that such shares as may be issued
pursuant to the exercise of this Warrant will, upon issuance, be duly and
validly issued, fully paid and nonassessable and free from all taxes, liens and
charges with respect to the issuance thereof.

     9. DIVIDENDS. If, after the Original Issue Date, the Company shall
subdivide the Common Stock, by split-up or otherwise, or combine the Common
Stock, or issue additional shares of Common Stock in payment of a stock dividend
on the Common Stock, the number of shares issuable on the exercise of this
Warrant shall forthwith be proportionately increased in the case of a
subdivision or stock dividend, or proportionately decreased in the case of a
combination, and the Purchase Price shall forthwith be proportionately decreased
in the case of a subdivision or stock dividend, or proportionately increased in
the case of a combination.

     10. MERGERS AND RECLASSIFICATIONS. If after the Original Issue Date there
shall be any reclassification, capital reorganization or change of the Common
Stock (other than as a result of a subdivision, combination or stock dividend
provided for in Section 9 hereof), or any consolidation of the Company with, or
merger of the Company into, another corporation or other business organization
(other than a consolidation or merger in which the Company is the continuing
corporation and which does not result in any reclassification or change of the
outstanding Common Stock), or any sale or conveyance to another corporation or
other business organization of all or substantially all of the assets of the
Company, then, as a condition of such reclassification, reorganization, change,
consolidation, merger, sale or conveyance, lawful provisions shall be made, and
duly executed documents evidencing the same from the Company or its successor
shall be delivered to the Holder, so that the Holder shall thereafter have the
right to purchase, at a total price not to exceed that payable upon the exercise
of this Warrant in full, the kind and amount of shares of stock and other
securities and property receivable upon such reclassification, reorganization,
change, consolidation, merger, sale or conveyance by a holder of the number of
shares of Common Stock which might have been purchased by the Holder immediately
prior to such reclassification, reorganization, change, consolidation, merger,
sale or conveyance, and in any such case appropriate provisions shall be made
with respect to the rights and interest of the Holder to the end that the
provisions hereof shall thereafter be applicable in relation to any shares of
stock or other securities and property thereafter deliverable upon exercise
hereof.

     11. FRACTIONAL SHARES. In no event shall any fractional share of Common
Stock be issued upon any exercise of this Warrant. If, upon exercise of this
Warrant as an entirety, the Holder would, except as provided in this Section 11,
be entitled to receive a fractional share of Common Stock, then the Company
shall pay to the Holder, in cash or by check, the cash value of such fractional
share, based upon the fair market value of one share of Common Stock as of the
date of exercise, as determined in good faith by the Board.

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     12. CERTIFICATE OF ADJUSTMENT. Whenever the Purchase Price is adjusted, as
herein provided, the Company shall promptly deliver to the Holder a certificate
setting forth the Purchase Price after such adjustment and setting forth a brief
statement of the facts requiring such adjustment.

     13. NOTICES OF RECORD DATE, ETC. In the event of:

         (a) any taking by the Company of a record of the holders of any class
     of securities for the purpose of determining the holders thereof who are
     entitled to receive any dividend or other distribution, or any right to
     subscribe for, purchase or otherwise acquire any shares of stock of any
     class or any other securities or property, or to receive any other right,

         (b) any reclassification of the capital stock of the Company, capital
     reorganization of the Company, consolidation or merger involving the
     Company, or sale or conveyance of all or substantially all of its assets,
     or

         (c) any voluntary or involuntary dissolution, liquidation or winding-up
     of the Company,

then and in each such event the Company will mail or cause to be mailed to the
Holder a notice specifying (i) the date on which any such record is to be taken
for the purpose of such dividend, distribution or right, and stating the amount
and character of such dividend, distribution or right, or (ii) the date on which
any such reclassification, reorganization, consolidation, merger, sale or
conveyance, dissolution, liquidation or winding-up is to take place, and the
time, if any is to be fixed, as of which the holders of record in respect of
such event are to be determined. Such notice shall be mailed at least 10 days
prior to the date specified in such notice on which any such action is to be
taken.

     14. AMENDMENT. The terms of this Warrant may be amended, modified or waived
only with the written consent of the Company and the holders of Warrants
representing at least two-thirds of the number of shares of Common Stock then
issuable upon the exercise of the Warrants. No such amendment, modification or
waiver shall be effective as to this Warrant unless the terms of such amendment,
modification or waiver shall apply with the same force and effect to all of the
other Warrants then outstanding.

     15. WARRANT REGISTER, LOST WARRANT, ETC.

         A. The Company will maintain a register containing the names and
     addresses of the registered holders of the Warrants. The Holder may change
     its address as shown on the warrant register by written notice to the
     Company requesting such change. Any notice or written communication
     required or permitted to be given to the Holder may be given by certified
     mail or delivered to the Holder at its address as shown on the warrant
     register.

         B. In case this Warrant shall be mutilated, lost, stolen or destroyed,
     the Company shall issue a new warrant of like tenor and denomination and
     deliver the same (i) in exchange and substitution for and upon surrender
     and cancellation of any mutilated

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     Warrant, or (ii) in lieu of any Warrant lost, stolen or destroyed, upon
     receipt of evidence reasonably satisfactory to the Company of the loss,
     theft or destruction of such Warrant (including a reasonably detailed
     affidavit with respect to the circumstances of any loss, theft or
     destruction) and of indemnity reasonably satisfactory to the Company.

         C. Subject to compliance with applicable federal and state securities
     laws, this Warrant may be transferred by the Holder with respect to any or
     all of the shares purchasable hereunder. Upon surrender of this Warrant to
     the Company, together with the assignment hereof properly endorsed, for
     transfer of this Warrant as an entirety by the Holder, the Company shall
     issue a new warrant of the same denomination to the assignee. Upon
     surrender of this Warrant to the Company, together with the assignment
     hereof properly endorsed, by the Holder for transfer with respect to a
     portion of the shares of Common Stock purchasable hereunder, the Company
     shall issue a new warrant to the assignee, in such denomination as shall be
     requested by the Holder hereof, and shall issue to such Holder a new
     warrant covering the number of shares in respect of which this Warrant
     shall not have been transferred.

     16. NO IMPAIRMENT. The Company will not, by amendment of its Amended and
Restated Certificate of Incorporation or through any reclassification, capital
reorganization, consolidation, merger, sale or conveyance of assets,
dissolution, liquidation, issue or sale of securities or any other voluntary
action, avoid or seek to avoid the observance or performance of any of the terms
of this Warrant, but will at all times in good faith assist in the carrying out
of all such terms and in the taking of all such action as may be necessary or
appropriate in order to protect the rights of the Holder.

     17. GOVERNING LAW. The provisions and terms of this Warrant shall be
governed by and construed in accordance with the internal laws of the
Commonwealth of Massachusetts without regard for the conflict of laws
principles therein.

     18. SUCCESSORS AND ASSIGNS. This Warrant shall be binding upon the
Company's successors and assigns and shall inure to the benefit of the Holder's
successors, legal representatives and permitted assigns.

     19. BUSINESS DAYS. If the last or appointed day for the taking of any
action required or the expiration of any right granted herein shall be a
Saturday or Sunday or a legal holiday in Massachusetts, then such action may be
taken or right may be exercised on the next succeeding day which is not a
Saturday or Sunday or such a legal holiday.

                  [Remainder of Page Intentionally Left Blank]

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                                           METABOLIX, INC.

Dated:
       ----------------------------

                                           By:
                                              ------------------------------
                                              Name:
                                              Title:

(Corporate Seal)

Attest:

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

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                                  SUBSCRIPTION
                   (To be signed only on exercise of Warrant)

To: Metabolix, Inc.                   Date:
                                           -----------------------------------

     The undersigned hereby subscribes for __________ shares of Common Stock
covered by this Warrant. The certificate(s) for such shares shall be issued in
the name of the undersigned or as otherwise indicated below:

                                      ----------------------------------------
                                      Signature

                                      ----------------------------------------
                                      Name for Registration

                                      ----------------------------------------
                                      Mailing Address

                            NET ISSUE ELECTION NOTICE

To:                                   Date:
   ---------------------------             -----------------------------------

     The undersigned hereby elects under Section 4 to surrender the right to
purchase _________ shares of Common Stock pursuant to this Warrant. The
certificate(s) for the shares issuable upon such net issue election shall be
issued in the name of the undersigned or as otherwise indicated below.

                                      ----------------------------------------
                                      Signature

                                      ----------------------------------------
                                      Name for Registration

                                      ----------------------------------------
                                      Mailing Address

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                                   ASSIGNMENT
                   (To be signed only on transfer of Warrant)

         For value received __________________________ hereby sells,

assigns and transfers unto ________________________________________

---------------------------------------------------------------------
 (Please print or typewrite name and address of Assignee)

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

the right represented by the within Warrant, and does hereby irrevocably
constitute and appoint _________________________ its attorney to transfer the
within Warrant on the books of the within named Company with full power of
substitution on the premises.

Dated:
       -------------------------------------

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

In the Presence of:

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                                                                    Exhibit 10.1

                                 METABOLIX INC.

                                 1995 STOCK PLAN

                        (as amended as of March 3, 2003)

     1.   PURPOSE. The purpose of the 1995 Stock Plan of Metabolix Inc. (the
"Plan") is to encourage key employees of Metabolix Inc. (the "Company") and of
any present or future parent or subsidiary of the Company (collectively,
"Related Corporations") and other individuals who render services to the Company
or a Related Corporation, by providing opportunities to participate in the
ownership of the Company and its future growth through (a) the grant of options
which qualify as "incentive stock options" ("ISOs") under Section 422(b) of the
Internal Revenue Code of 1986, as amended (the "Code"); (b) the grant of options
which do not qualify as ISOs ("Non-Qualified Options"); (c) awards of stock in
the Company ("Awards"); and (d) opportunities to make direct purchases of stock
in the Company ("Purchases"). Both ISOs and Non-Qualified Options are referred
to hereafter individually as an "Option" and collectively as "Options," Options,
Awards and authorizations to make Purchases are referred to hereafter
collectively as "Stock Rights." As used herein, the terms "parent" and
"subsidiary" mean "parent corporation" and "subsidiary corporation,"
respectively, as those terms are defined in Section 424 of the Code.

     2.   ADMINISTRATION OF THE PLAN.

          A.   BOARD OR COMMITTEE ADMINISTRATION. The Plan shall be administered
     by the Board of Directors of the Company (the "Board") or by a committee
     appointed by the Board (the "Committee"); provided that the Plan shall be
     administered: (i) to the extent required by applicable regulations under
     Section 162(m) of the Code, by two or more "outside directors" (as defined
     in applicable regulations thereunder) and (ii) to the extent required by
     Rule 16b-3 promulgated under the Securities Exchange Act of 1934 or any
     successor provision ("Rule 16b-3"), by a disinterested administrator or
     administrators within the meaning of Rule 16b-3. Hereinafter, all
     references in this Plan to the "Committee" shall mean the Board if no
     Committee has been appointed. Subject to ratification of the grant or
     authorization of each Stock Right by the Board (if so required by
     applicable state law), and subject to the terms of the Plan, the Committee
     shall have the authority to (i) determine to whom (from among the class of
     employees eligible under paragraph 3 to receive ISOs) ISOs shall be
     granted, and to whom (from among the class of individuals and entities
     eligible under paragraph 3 to receive Non-Qualified Options and Awards and
     to make Purchases) Non-Qualified Options, Awards and authorizations to make
     Purchases may be granted; (ii) determine the time or times at which Options
     or Awards shall be granted or Purchases made; (iii) determine the purchase
     price of shares subject to each Option or Purchase, which prices shall not
     be less than the minimum price specified in paragraph 6; (iv) determine
     whether each Option granted shall be an ISO or a Non-Qualified Option; (v)
     determine (subject to paragraph 7) the time or times when each Option shall
     become exercisable and the duration of the exercise period; (vi) extend the
     period during which outstanding Options may be exercised; (vii) determine
     whether restrictions such as repurchase options are to be imposed on shares
     subject to Options, Awards and Purchases and the nature of such
     restrictions, if any, and (viii) interpret the Plan and prescribe and
     rescind rules and regulations relating to it. If the Committee determines
     to issue a Non-Qualified Option, it shall take whatever actions it deems
     necessary, under Section 422 of the Code and the regulations promulgated
     thereunder, to ensure that such Option is not treated as an ISO. The
     interpretation

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                                       -2-

     and construction by the Committee of any provisions of the Plan or of any
     Stock Right granted under it shall be final unless otherwise determined by
     the Board. The Committee may from time to time adopt such rules and
     regulations for carrying out the Plan as it may deem advisable. No member
     of the Board or the Committee shall be liable for any action or
     determination made in good faith with respect to the Plan or any Stock
     Right granted under it.

          B.   COMMITTEE ACTIONS. The Committee may select one of its members as
     its chairman, and shall hold meetings at such time and places as it may
     determine. A majority of the Committee shall constitute a quorum and acts
     of a majority of the members of the Committee at a meeting at which a
     quorum is present, or acts reduced to or approved in writing by all the
     members of the Committee (if consistent with applicable state law), shall
     be the valid acts of the Committee. From time to time the Board may
     increase the size of the Committee and appoint additional members thereof,
     remove members (with or without cause) and appoint new members in
     substitution therefor, fill vacancies however caused, or remove all members
     of the Committee and thereafter directly administer the Plan.

          C.   GRANT OF STOCK RIGHTS TO BOARD MEMBERS. Subject to the provisions
     of the first sentence of paragraph 2(A) above, if applicable, Stock Rights
     may be granted to members of the Board. All grants of Stock Rights to
     members of the Board shall in all other respects be made in accordance with
     the provisions of this Plan applicable to other eligible persons.
     Consistent with the provisions of the first sentence of Paragraph 2(A)
     above, members of the Board who either (i) are eligible to receive grants
     of Stock Rights pursuant to the Plan or (ii) have been granted Stock Rights
     may vote on any matters affecting the administration of the Plan or the
     grant of any Stock Rights pursuant to the Plan, except that no such member
     shall act upon the granting to himself or herself of Stock Rights, but any
     such member may be counted in determining the existence of a quorum at any
     meeting of the Board during which action is taken with respect to the
     granting to such member of Stock Rights.

     3.   ELIGIBLE EMPLOYEES AND OTHERS. ISOs may be granted only to employees
of the Company or any Related Corporation. Non-Qualified Options, Awards and
authorizations to make Purchases may be granted to any employee, officer or
director (whether or not also an employee) or consultant of the Company or any
Related Corporation. The Committee may take into consideration a recipient's
individual circumstances in determining whether to grant a Stock Right. The
granting of any Stock Right to any individual or entity shall neither entitle
that individual or entity to, nor disqualify such individual or entity from,
participation in any other grant of Stock Rights.

     4.   STOCK. The stock subject to Stock Rights shall be authorized but
unissued shares of Common Stock of the Company, par value $.01 per share (the
"Common Stock"), or shares of Common Stock reacquired by the Company in any
manner. The aggregate number of shares which may be issued pursuant to the Plan
is one million (1,000,000), subject to adjustment as provided in paragraph 13
(such number reflects adjustment for all stock splits of the Company's Common
Stock, $.01 par value, effected in, or prior to September 1998). If any Stock
Right granted under the Plan shall expire or terminate for any reason without
having been exercised in full or shall cease for any reason to be exercisable in
whole or in part or shall be repurchased by the Company, the shares of Common
Stock subject to such Stock Right shall again be available for grants of Stock
Rights under the Plan.

     5.   GRANTING OF STOCK RIGHTS. Stock Rights may be granted under the Plan
at any time on or after June 6, 1995 and prior to June 6, 2005. The date of
grant of a Stock Right under the Plan will be

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                                       -3-

the date specified by the Committee at the time it grants the Stock Right;
provided, however, that such date shall not be prior to the date on which the
Committee acts to approve the grant.

     6.   MINIMUM OPTION PRICE; ISO LIMITATIONS.

          A.   PRICE FOR NON-QUALIFIED OPTIONS. AWARDS AND PURCHASES. The
     exercise price per share specified in the agreement relating to each
     Non-Qualified Option granted, and the purchase price per share of stock
     granted in any Award or authorized Purchase, under the Plan shall in no
     event be less than the minimum legal consideration required therefor under
     the laws of any jurisdiction in which the Company or its successors in
     interest may be organized.

          B.   PRICE FOR ISOs. The exercise price per share specified in the
     agreement relating to each ISO granted under the Plan shall not be less
     than the fair market value per share of Common Stock on the date of such
     grant. In the case of an ISO to be granted to an employee owning stock
     possessing more than ten percent (10%) of the total combined voting power
     of all classes of stock of the Company or any Related Corporation, the
     price per share specified in the agreement relating to such ISO shall not
     be less than one hundred ten percent (110%) of the fair market value per
     share of Common Stock on the date of grant. For purposes of determining
     stock ownership under this paragraph, the rules of Section 424(d) of the
     Code shall apply.

          C.   $100.000 ANNUAL LIMITATION ON ISO VESTING. Each eligible employee
     may be granted Options treated as ISOs only to the extent that, in the
     aggregate under this Plan and all incentive stock option plans of the
     Company and any Related Corporation, ISOs do not become exercisable for the
     first time by such employee during any calendar year with respect to stock
     having a fair market value (determined at the time the ISOs were granted)
     in excess of $100,000. The Company intends to designate any Options granted
     in excess of such limitation as Non-Qualified Options.

          D.   DETERMINATION OF FAIR MARKET VALUE. If, at the time an Option is
     granted under the Plan, the Company's Common Stock is publicly traded,
     "fair market value" shall be determined as of the date of grant or, if the
     prices or quotes discussed in this sentence are unavailable for such date,
     the last business day for which such prices or quotes are available prior
     to the date of grant, and shall mean (i) the average (on that date) of the
     high and low prices of the Common Stock on the principal national
     securities exchange on which the Common Stock is traded, if the Common
     Stock is then traded on a national securities exchange; or (ii) the last
     reported sale price (on that date) of the Common Stock on the Nasdaq
     National Market, if the Common Stock is not then traded on a national
     securities exchange; or (iii) the closing bid price (or average of bid
     prices) last quoted (on that date) by an established quotation service for
     over-the-counter securities, if the Common Stock is not reported on the
     Nasdaq National Market. If the Common Stock is not publicly traded at the
     time an Option is granted under the Plan, "fair market value" shall mean
     the fair value of the Common Stock as determined by the Committee after
     taking into consideration all factors which it deems appropriate,
     including, without limitation, recent sale and offer prices of the Common
     Stock in private transactions negotiated at arm's length.

     7.   OPTION DURATION. Subject to earlier termination as provided in
paragraphs 9 and 10 or in the agreement relating to such Option, each Option
shall expire on the date specified by the Committee, but not more than (i) ten
years from the date of grant in the case of Options generally and (ii) five
years from the date of grant in the case of ISOs granted to an employee owning
stock possessing

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                                       -4-

more than ten percent (10%) of the total combined voting power of all classes of
stock of the Company or any Related Corporation, as determined under paragraph
6(B). Subject to earlier termination as provided in paragraphs 9 and 10, the
term of each ISO shall be the term set forth in the original instrument granting
such ISO, except with respect to any part of such ISO that is converted into a
Non-Qualified Option pursuant to paragraph 16.

     8.   EXERCISE OF OPTION. Subject to the provisions of paragraphs 9 through
12, each Option granted under the Plan shall be exercisable as follows:

          A.   VESTING. The Option shall either be fully exercisable on the date
     of grant or shall become exercisable thereafter in such installments as the
     Committee may specify.

          B.   FULL VESTING OF INSTALLMENTS. Once an installment becomes
     exercisable it shall remain exercisable until expiration or termination of
     the Option, unless otherwise specified by the Committee,

          C.   PARTIAL EXERCISE. Each Option or installment may be exercised at
     any time or from time to time, in whole or in part, for up to the total
     number of shares with respect to which it is then exercisable,

          D.   ACCELERATION OF VESTING. The Committee shall have the right to
     accelerate the date that any installment of any Option becomes exercisable;
     provided that the Committee shall not, without the consent of an optionee,
     accelerate the permitted exercise date of any installment of any Option
     granted to any employee as an ISO (and not previously converted into a Non-
     Qualified Option pursuant to paragraph 16) if such acceleration would
     violate the annual vesting limitation contained in Section 422(d) of the
     Code, as described in paragraph 6(C).

     9.   TERMINATION OF EMPLOYMENT. Unless otherwise specified in the agreement
relating to such ISO, if an ISO optionee ceases to be employed by the Company
and all Related Corporations other than by reason of death or disability as
defined in paragraph 10, no further installments of his or her ISOs shall become
exercisable, and his or her ISOs shall terminate on the earlier of (a) sixty
(60) days after the date of termination of his or her employment, or (b) their
specified expiration dates, except to the extent that such ISOs (or unexercised
installments thereof) have been converted into Non-Qualified Options pursuant to
paragraph 16. For purposes of this paragraph 9, employment shall be considered
as continuing uninterrupted during any bona fide leave of absence (such as those
attributable to illness, military obligations or governmental service) provided
that the period of such leave does not exceed 90 days or, if longer, any period
during which such optionee's right to reemployment is guaranteed by statute. A
bona fide leave of absence with the written approval of the Committee shall not
be considered an interruption of employment under this paragraph 9, provided
that such written approval contractually obligates the Company or any Related
Corporation to continue the employment of the optionee after the approved period
of absence. ISOs granted under the Plan shall not be affected by any change of
employment within or among the Company and Related Corporations, so long as the
optionee continues to be an employee of the Company or any Related Corporation.
Nothing in the Plan shall be deemed to give any grantee of any Stock Right the
right to be retained in employment or other service by the Company or any
Related Corporation for any period of time.

     10.  DEATH: DISABILITY.

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                                       -5-

          A.   DEATH. If an ISO optionee ceases to be employed by the Company
     and all Related Corporations by reason of his or her death, any ISO owned
     by such optionee may be exercised, to the extent otherwise exercisable on
     the date of death, by the estate, personal representative or beneficiary
     who has acquired the ISO by will or by the laws of descent and
     distribution, until the earlier of (i) the specified expiration date of the
     ISO or (ii) 180 days from the date of the optionee's death.

          B.   DISABILITY. If an ISO optionee ceases to be employed by the
     Company and all Related Corporations by reason of his or her disability,
     such optionee shall have the right to exercise any ISO held by him or her
     on the date of termination of employment, for the number of shares for
     which he or she could have exercised it on that date, until the earlier of
     (i) the specified expiration date of the ISO or (ii) 180 days from the date
     of the termination of the optionee's employment. For the purposes of the
     Plan, the term "disability" shall mean "permanent and total disability" as
     defined in Section 22(e)(3) of the Code or any successor statute.

     11.  ASSIGNABILITY. No Stock Right shall be assignable or transferable by
the grantee except by will, by the laws of descent and distribution or, in the
case of Non-Qualified Options only, pursuant to a valid domestic relations
order. Except as set forth in the previous sentence, during the lifetime of a
grantee each Stock Right shall be exercisable only by such grantee.

     12.  TERMS AND CONDITIONS OF OPTIONS. Options shall be evidenced by
instruments (which need not be identical) in such forms as the Committee may
from time to time approve. Such instruments shall conform to the terms and
conditions set forth in paragraphs 6 through 11 hereof and may contain such
other provisions as the Committee deems advisable which are not inconsistent
with the Plan, including restrictions applicable to shares of Common Stock
issuable upon exercise of Options. The Committee may specify that any
Non-Qualified Option shall be subject to the restrictions set forth herein with
respect to ISOs, or to such other termination and cancellation provisions as the
Committee may determine. The Committee may from time to time confer authority
and responsibility on one or more of its own members and/or one or more officers
of the Company to execute and deliver such instruments. The proper officers of
the Company are authorized and directed to take any and all action necessary or
advisable from time to time to carry out the terms of such instruments.

     13.  ADJUSTMENTS. Upon the occurrence of any of the following events, an
optionee's rights with respect to Options granted to such optionee hereunder
shall be adjusted as hereinafter provided, unless otherwise specifically
provided in the written agreement between the optionee and the Company relating
to such Option:

          A.   STOCK DIVIDENDS AND STOCK SPLITS. If the shares of Common Stock
     shall be subdivided or combined into a greater or smaller number of shares
     or if the Company shall issue any shares of Common Stock as a stock
     dividend on its outstanding Common Stock, the number of shares of Common
     Stock deliverable upon the exercise of Options shall be appropriately
     increased or decreased proportionately, and appropriate adjustments shall
     be made in the purchase price per share to reflect such subdivision,
     combination or stock dividend.

          B.   CONSOLIDATIONS OR MERGERS. If the Company is to be consolidated
     with or acquired by another entity in a merger, sale of all or
     substantially all of the Company's assets or otherwise (an "Acquisition"),
     the Committee or the board of directors of any entity assuming the
     obligations of the Company hereunder (the "Successor Board"), shall, as to
     outstanding Options,

<Page>

                                       -6-

either (i) make appropriate provision for the continuation of such Options by
substituting on an equitable basis for the shares then subject to such Options
either (a) the consideration payable with respect to the outstanding shares of
Common Stock in connection with the Acquisition, (b) shares of stock of the
surviving corporation or (c) such other securities as the Successor Board deems
appropriate, the fair market value of which shall not materially exceed the fair
market value of the shares of Common Stock subject to such Options immediately
preceding the Acquisition; or (ii) upon written notice to the optionees, provide
that all Options must be exercised, to the extent then exercisable, within a
specified number of days of the date of such notice, at the end of which period
the Options shall terminate; or (iii) terminate all Options in exchange for a
cash payment equal to the excess of the fair market value of the shares subject
to such Options (to the extent then exercisable) over the exercise price
thereof.

     C.   RECAPITALIZATION OR REORGANIZATION. In the event of a recapitalization
or reorganization of the Company (other than a transaction described in
subparagraph B above) pursuant to which securities of the Company or of another
corporation are issued with respect to the outstanding shares of Common Stock,
an optionee upon exercising an Option shall be entitled to receive for the
purchase price paid upon such exercise the securities he or she would have
received if he or she had exercised such Option prior to such recapitalization
or reorganization.

     D.   MODIFICATION OF ISOs. Notwithstanding the foregoing, any adjustments
made pursuant to subparagraphs A, B or C with respect to ISOs shall be made only
after the Committee, after consulting with counsel for the Company, determines
whether such adjustments would constitute a "modification" of such ISOs (as that
term is defined in Section 424 of the Code) or would cause any adverse tax
consequences for the holders of such ISOs. If the Committee determines that such
adjustments made with respect to ISOs would constitute a modification of such
ISOs or would cause adverse tax consequences to the holders, it may refrain from
making such adjustments.

     E.   DISSOLUTION OR LIQUIDATION. In the event of the proposed dissolution
or liquidation of the Company, each Option will terminate immediately prior to
the consummation of such proposed action or at such other time and subject to
such other conditions as shall be determined by the Committee.

     F.   ISSUANCES OF SECURITIES. Except as expressly provided herein, no
issuance by the Company of shares of stock of any class, or securities
convertible into shares of stock of any class, shall affect, and no adjustment
by reason thereof shall be made with respect to, the number or price of shares
subject to Options. No adjustments shall be made for dividends paid in cash or
in property other than securities of the Company.

     G.   FRACTIONAL SHARES. No fractional shares shall be issued under the Plan
and the optionee shall receive from the Company cash in lieu of such fractional
shares.

     H.   ADJUSTMENTS. Upon the happening of any of the events described in
subparagraphs A, B or C above, the class and aggregate number of shares set
forth in paragraph 4 hereof that are subject to Stock Rights which previously
have been or subsequently may be granted under the Plan shall also be
appropriately adjusted to reflect the events described in such subparagraphs.
The Committee or the Successor Board shall determine the specific adjustments to
be made under this paragraph 13 and, subject to paragraph 2, its determination
shall be conclusive.

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                                       -7-

     14.  MEANS OF EXERCISING OPTIONS. An Option (or any part or installment
thereof) shall be exercised by giving written notice to the Company at its
principal office address, or to such transfer agent as the Company shall
designate. Such notice shall identify the Option being exercised and specify the
number of shares as to which such Option is being exercised, accompanied by full
payment of the purchase price therefor either (a) in United States dollars in
cash or by check, (b) at the discretion of the Committee, through delivery of
shares of Common Stock having a fair market value equal as of the date of the
exercise to the cash exercise price of the Option, (c) at the discretion of the
Committee, by delivery of the grantee's personal recourse note bearing interest
payable not less than annually at no less than 100% of the lowest applicable
Federal rate, as defined in Section 1274(d) of the Code, (d) at the discretion
of the Committee and consistent with applicable law, through the delivery of an
assignment to the Company of a sufficient amount of the proceeds from the sale
of the Common Stock acquired upon exercise of the Option and an authorization to
the broker or selling agent to pay that amount to the Company, which sale shall
be at the participant's direction at the time of exercise, or (e) at the
discretion of the Committee, by any combination of (a), (b), (c) and (d) above.
If the Committee exercises its discretion to permit payment of the exercise
price of an ISO by means of the methods set forth in clauses (b), (c), (d) or
(e) of the preceding sentence, such discretion shall be exercised in writing at
the time of the grant of the ISO in question. The holder of an Option shall not
have the rights of a shareholder with respect to the shares covered by such
Option until the date of issuance of a stock certificate to such holder for such
shares. Except as expressly provided above in paragraph 13 with respect to
changes in capitalization and stock dividends, no adjustment shall be made for
dividends or similar rights for which the record date is before the date such
stock certificate is issued.

     15.  TERM AND AMENDMENT OF PLAN. This Plan was adopted by the Board on
June 6, 1995, subject, with respect to the validation of ISOs granted under the
Plan, to approval of the Plan by the stockholders of the Company at the next
Meeting of Stockholders or, in lieu thereof, by written consent. If the approval
of stockholders is not obtained prior to June 6, 1996, any grants of ISOs under
the Plan made prior to that date will be rescinded. The Plan shall expire at the
end of the day on June 6, 2005 (except as to Options outstanding on that date).
Subject to the provisions of paragraph 5 above. Options may be granted under the
Plan prior to the date of stockholder approval of the Plan. The Board may
terminate or amend the Plan in any respect at any time, except that, without the
approval of the stockholders obtained within 12 months before or after the Board
adopts a resolution authorizing any of the following actions: (a) the total
number of shares that may be issued under the Plan may not be increased (except
by adjustment pursuant to paragraph 13); (b) the benefits accruing to
participants under the Plan may not be materially increased; (c) the
requirements as to eligibility for participation in the Plan may not be
materially modified; (d) the provisions of paragraph 3 regarding eligibility for
grants of ISOs may not be modified; (e) the provisions of paragraph 6(B)
regarding the exercise price at which shares may be offered pursuant to ISOs may
not be modified (except by adjustment pursuant to paragraph 13); (f) the
expiration date of the Plan may not be extended; and (g) the Board may not take
any action which would cause the Plan to fail to comply with Rule 16b-3. Except
as otherwise provided in this paragraph 15, in no event may action of the Board
or stockholders alter or impair the rights of a grantee, without such grantee's
consent, under any Option previously granted to such grantee.

     16.  CONVERSION OF ISOs INTO NON-QUALIFIED OPTIONS. The Committee, at the
written request or with the written consent of any optionee, may in its
discretion take such actions as may be necessary to convert such optionee's ISOs
(or any installments or portions of installments thereof) that have not been
exercised on the date of conversion into Non-Qualified Options at any time prior
to the expiration of such ISOs, regardless of whether the optionee is an
employee of the Company or a Related Corporation at the time of such conversion.
Such actions may include, but shall not be limited to,

<Page>

                                       -8-

extending the exercise period or reducing the exercise price of the appropriate
installments of such ISOs. At the time of such conversion, the Committee (with
the consent of the optionee) may impose such conditions on the exercise of the
resulting Non-Qualified Options as the Committee in its discretion may
determine, provided that such conditions shall not be inconsistent with this
Plan. Nothing in the Plan shall be deemed to give any optionee the right to have
such optionee's ISOs converted into Non-Qualified Options, and no such
conversion shall occur until and unless the Committee takes appropriate action.

     17.  APPLICATION OF FUNDS. The proceeds received by the Company from the
sale of shares pursuant to Options granted and Purchases authorized under the
Plan shall be used for general corporate purposes.

     18.  NOTICE TO COMPANY OF DISQUALIFYING DISPOSITION. By accepting an ISO
granted under the Plan, each optionee agrees to notify the Company in writing
immediately after such optionee makes a Disqualifying Disposition (as described
in Sections 421, 422 and 424 of the Code and regulations thereunder) of any
stock acquired pursuant to the exercise of ISOs granted under the Plan. A
Disqualifying Disposition is generally any disposition occurring on or before
the later of (a) the date two years following the date the ISO was granted or
(b) the date one year following the date the ISO was exercised.

     19.  WITHHOLDING OF ADDITIONAL INCOME TAXES. Upon the exercise of a
Non-Qualified Option, the grant of an Award, the making of a Purchase of Common
Stock for less than its fair market value, the making of a Disqualifying
Disposition (as defined in paragraph 18), the vesting or transfer of restricted
stock or securities acquired on the exercise of an Option hereunder, or the
making of a distribution or other payment with respect to such stock or
securities, the Company may withhold taxes in respect of amounts that constitute
compensation includible in gross income. The Committee in its discretion may
condition (i) the exercise of an Option, (ii) the grant of an Award, (iii) the
making of a Purchase of Common Stock for less than its fair market value, or
(iv) the vesting or transferability of restricted stock or securities acquired
by exercising an Option, on the grantee's making satisfactory arrangement for
such withholding. Such arrangement may include payment by the grantee in cash or
by check of the amount of the withholding taxes or, at the discretion of the
Committee, by the grantee's delivery of previously held shares of Common Stock
or the withholding from the shares of Common Stock otherwise deliverable upon
exercise of a Option shares having an aggregate fair market value equal to the
amount of such withholding taxes.

     20.  GOVERNMENTAL REGULATION. The Company's obligation to sell and deliver
shares of the Common Stock under this Plan is subject to the approval of any
governmental authority required in connection with the authorization, issuance
or sale of such shares.

          Government regulations may impose reporting or other obligations on
the Company with respect to the Plan. For example, the Company may be required
to send tax information statements to employees and former employees that
exercise ISOs under the Plan, and the Company may be required to file tax
information returns reporting the income received by grantees of Options in
connection with the Plan.

     21.  GOVERNING LAW. The validity and construction of the Plan and the
instruments evidencing Options shall be governed by the laws of the Commonwealth
of Massachusetts, or the laws of any jurisdiction in which the Company or its
successors in interest may be organized.

<Page>

                                       -9-

                  REGISTER OF AMENDMENTS TO THE 1995 STOCK PLAN

APRIL 4, 1996 AT THE ANNUAL MEETING OF STOCKHOLDERS:

a.   Paragraph 4 was adjusted to change the number of authorized shares from 109
     to 10,900 shares in connection with a 100-for-one stock split of the
     Company's Common Stock, $.01 par value.

FEBRUARY 12, 1998 AMENDED BY BOARD OF DIRECTORS, RATIFIED BY STOCKHOLDERS ON
NOVEMBER 19, 1998

a.   Paragraph 4 was amended to increase the number of authorized shares from
     10,900 to 13,400 shares.

SEPTEMBER 2, 1998 AMENDED BY BOARD OF DIRECTORS AND RATIFIED BY THE STOCKHOLDERS

a.   Paragraph 4 was amended to increase the number of authorized shares from
     13,400 to 134,000 shares in connection with a 10-for-l stock split.

NOVEMBER 19, 1998 AMENDED BY BOARD OF DIRECTORS, AND RATIFIED BY THE
STOCKHOLDERS

a.   Paragraph 4 was amended to increase the number of authorized shares from
     134,000 to 200,000 shares.

NOVEMBER 24, 1999 AMENDED BY BOARD OF DIRECTORS, AND RATIFIED BY THE
STOCKHOLDERS

a.   Paragraph 4 was amended to increase the number of authorized shares from
     200,000 to 550,000 shares.

MARCH 8, 2000 AMENDED BY BOARD OF DIRECTORS, AND RATIFIED BY THE STOCKHOLDERS

a.   Paragraph 4 was amended to increase the number of authorized shares from
     550,000 to 665,000 shares

MARCH 3, 2003 AMENDED BY BOARD OF DIRECTORS, AND RATIFIED BY THE STOCKHOLDERS ON
APRIL 10, 2003

a.   Paragraph 4 was amended to increase the number of authorized shares from
     665,000 to 1,000,000 shares

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