Document:

<PAGE>   1
                                                                     EXHIBIT 4.1

                             LETTER OF TRANSMITTAL
                              with respect to the
                            Exchange of Common Stock
                                       of
                              BARGO ENERGY COMPANY
                           For Shares of Common Stock
                                       of
                         MISSION RESOURCES CORPORATION

     Mail or deliver this Letter of Transmittal, or a facsimile hereof, together
with the certificates representing your shares to American Stock Transfer and
Trust Company, the Exchange Agent, at the following addresses:

<TABLE>
<CAPTION>

           By Hand:                           By First Class Mail:                   By Overnight Carrier or
                                                                                         Certified Mail:
<S>                                     <C>                                      <C>
  6201 15th Ave., Third Floor             6201 15th Ave., Third Floor              6201 15th Ave., Third Floor
      Brooklyn, NY 11219                      Brooklyn, NY 11219                       Brooklyn, NY 11219
Attn: Reorganization Department         Attn: Reorganization Department          Attn: Reorganization Department
</TABLE>

     For information, contact American Stock Transfer and Trust Company at
1-800-937-5449.

                       DESCRIPTION OF SHARES SURRENDERED

<TABLE>
<CAPTION>
                            (1)                                                 (2)                           (3)
                                                                      CERTIFICATE NUMBER(S)
        NAME AND ADDRESS(ES) OF REGISTERED HOLDER(S)                 (ATTACH ADDITIONAL LIST           NUMBER OF SHARES
(PLEASE FILL IN EXACTLY AS NAME(S) APPEAR ON CERTIFICATE(S))              IF NECESSARY)             DELIVERED FOR EXCHANGE
------------------------------------------------------------         -----------------------        ----------------------
<S>                                                                  <C>                            <C>
                                                                     -----------------------        ----------------------

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

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

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

                                                                     -----------------------        ----------------------
                                                                           Total Shares
------------------------------------------------------------         -----------------------        ----------------------
</TABLE>

Please issue one certificate for the shares of Mission Common Stock to which the
undersigned is entitled in the name of the undersigned shown above (unless a
different name is indicated in the Special Issuance Instructions box below),
for delivery by mail to the address shown above (unless a different address is
indicated in the Special Delivery Instructions box or the Special Issuance
Instructions box below).

<PAGE>   2
Ladies and Gentlemen:

         In connection with the merger (the "MERGER") of Bargo Energy Company, a
Texas corporation ("BARGO"), with and into Bellwether Exploration Company, a
Delaware corporation ("BELLWETHER"), which, at the effective time of the merger
(the "EFFECTIVE TIME"), will be renamed Mission Resources Corporation ("MISSION
RESOURCES"), and pursuant to the Agreement and Plan of Merger dated January 24,
2001 (the "MERGER AGREEMENT"), as described in the joint proxy
statement/prospectus/annual report of Bargo and Bellwether dated April 24,
2001 (the "PROSPECTUS"), the undersigned hereby surrenders the number of shares
of common stock of Bargo, par value $0.01 per share ("BARGO COMMON STOCK"),
represented by the certificate(s) described above (the "CERTIFICATES"), in
exchange for $0.45 in cash (the "CASH CONSIDERATION") and 0.0958 shares of
Mission common stock, par value $0.01 per share ("MISSION COMMON STOCK"), for
each share of Bargo Common Stock tendered hereby. Undefined capitalized terms
herein are defined in the Merger Agreement.

         All authority herein conferred or agreed to be conferred shall survive
the death or incapacity of the undersigned, and any obligation of the
undersigned hereunder shall be binding upon the heirs, personal representatives,
estates, successors and assigns of the undersigned. The undersigned hereby
represents and warrants that the undersigned is the owner of the shares of Bargo
Common Stock delivered hereby and has full power and authority to submit and
exchange the shares of Bargo Common Stock delivered for exchange hereby. The
undersigned will, upon request, execute and deliver any additional documents
deemed by the Exchange Agent or Mission Resources to be necessary or desirable
to complete the exchange of the shares of Bargo Common Stock tendered for
exchange hereby.

         The undersigned hereby irrevocably constitutes and appoints the
Exchange Agent the true and lawful attorney-in-fact of the undersigned with
respect to the Certificates with full power of substitution (such power of
attorney being deemed to be an irrevocable power coupled with an interest) to
deliver such Certificates on the account books maintained by and to deliver as
the undersigned's agent the shares of Mission Common Stock to which the
undersigned is entitled upon the surrender of the Certificates.

         The undersigned understands and agrees that the method of delivery of
the shares of Bargo Common Stock and this Letter of Transmittal is at the
election and risk of the holder of the shares of Bargo Common Stock. If delivery
of the shares of Bargo Common Stock is by mail, registered mail with return
receipt requested, properly insured, is recommended. Neither this Letter of
Transmittal nor any shares of Bargo Common Stock should be sent to Mission
Resources.

         The undersigned hereby acknowledges that the undersigned has read the
Instructions accompanying this Letter of Transmittal.

<PAGE>   3
--------------------------------------------------------------------------------

                          SPECIAL ISSUANCE INSTRUCTIONS
                          (See Instructions 2, 4 and 6)

(To be completed only if the certificates for shares of Mission Common Stock and
the Cash Consideration are to be issued in the name of someone other than the
undersigned.)

Issue and mail shares of Mission Common Stock to:

    Name:
         ------------------------------------------------------------
                                (Please Print)

    Address:
            ---------------------------------------------------------

    -----------------------------------------------------------------
    (City)                          (State)                     (ZIP)

                         (COMPLETE SUBSTITUTE FORM W-9)

                   (Tax Identification or Social Security No.)

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

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

                          SPECIAL DELIVERY INSTRUCTIONS
                          (See Instructions 2, 4 and 6)

(To be completed only if the certificates for shares of Mission Common Stock and
the Cash Consideration are to be mailed to the undersigned at an address other
than that shown on the record address.)

Mail shares of Mission Common Stock to:

    Name:
         ------------------------------------------------------------
                                (Please Print)

    Address:
            ---------------------------------------------------------

    -----------------------------------------------------------------
    (City)                          (State)                     (ZIP)

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

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

BY EXECUTING THIS LETTER OF TRANSMITTAL, THE UNDERSIGNED HEREBY DELIVERS TO
MISSION RESOURCES FOR EXCHANGE THE SECURITIES INDICATED IN THE BOX ENTITLED
"DESCRIPTION OF SHARES SURRENDERED."

                                   SIGN HERE
                              (See Instruction 4)
                         (Complete Substitute Form W-9)

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

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

    -----------------------------------------------------------------
                       (Signature(s) of Holder(s))

    Dated:                                                , 2001
          ------------------------------------------------

    Name:
         ------------------------------------------------------------
                                (Please Print)

         ------------------------------------------------------------
           (Title of signer if acting in a representative capacity)

    Address:
            ---------------------------------------------------------

    -----------------------------------------------------------------
    (City)                          (State)                     (ZIP)

Telephone Number
                -----------------------------------------------------

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

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

                          SIGNATURE(S) GUARANTEED BY:

                      (To be completed only if required by
                             Instructions 2 and 4)

The undersigned hereby guarantees the signature(s) which appear(s) on this
Letter of Transmittal and the Certificates and any stock powers surrendered
pursuant to this Letter of Transmittal.

    -----------------------------------------------------------------
                 (Name of Institution Issuing Guarantee)

    By:
       --------------------------------------------------------------
                           (Authorized Signature)

    Title:
          -----------------------------------------------------------

    Address of Guaranteeing Firm:
                                 ------------------------------------

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

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

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

--------------------------------------------------------------------------------
<PAGE>   4

                                  INSTRUCTIONS

     FORMING PART OF THE TERMS AND CONDITIONS OF THIS LETTER OF TRANSMITTAL

         1. Use of Letter of Transmittal. This Letter of Transmittal, properly
completed and duly executed, together with the surrendered Certificates and any
documents required by this Letter of Transmittal, should be sent by mail or
overnight courier or delivered by hand to the Exchange Agent, in each case at
the appropriate address set forth on the front page of this Letter of
Transmittal, in order to make an effective surrender. Until all necessary steps
have been taken to surrender Certificates, no exchange shall be made. The method
of delivery of all documents is at the option and risk of the undersigned and
the delivery will be deemed made only when actually received. If delivery is by
mail, registered mail with return receipt requested, properly insured, is
recommended. A return envelope is enclosed for your convenience.

         2. Guarantee of Signatures. Signatures on this Letter of Transmittal
must be guaranteed in accordance with Rule 17Ad-15 (promulgated under the
Securities Exchange Act of 1934) by an eligible guarantor institution which is a
participant in a stock transfer association recognized program, such as a firm
that is a member of a registered national securities exchange, a member of the
National Association of Securities Dealers, Inc., by a commercial bank or trust
company having an office or correspondent in the United States or by an
international bank, securities dealer, securities broker or other financial
institution licensed to do business in its home country (an "ELIGIBLE
INSTITUTION") unless (i) the Letter of Transmittal is signed by the registered
holder(s) of the shares of Bargo Common Stock tendered therewith and such
holder(s) have not completed the "Special Issuance Instructions" or "Special
Delivery Instructions" above or (ii) the shares of Bargo Common Stock described
above are delivered for the account of an Eligible Institution. IN ALL OTHER
CASES ALL SIGNATURES MUST BE GUARANTEED BY AN ELIGIBLE INSTITUTION.

         3. Inadequate Space. If the space provided in the box entitled
"Description of Shares Surrendered" above is inadequate, the certificate numbers
and number of shares of Bargo Common Stock being delivered should be listed on a
separate signed schedule affixed hereto.

         4. Signatures on this Letter of Transmittal, Powers of Attorney and
Endorsements.

          (a)  If this Letter of Transmittal is signed by the registered
               holder(s) of the shares of Bargo Common Stock delivered herewith,
               the signature(s) of the holder on this Letter of Transmittal must
               correspond exactly with the name(s) as written on the face of the
               Certificate without alteration, or any change whatsoever.

          (b)  If any shares of Bargo Common Stock are owned of record by two or
               more joint owners, all such owners must sign this Letter of
               Transmittal.

          (c)  If any shares of Bargo Common Stock are registered in different
               names on different Certificates, it will be necessary to
               complete, sign and submit as many separate copies of this Letter
               of Transmittal and any necessary or required documents as there
               are different registrations of Certificates.

<PAGE>   5

          (d)  Do not endorse the Certificates if the Mission Common Stock
               certificate is to be issued in the name of the registered
               holder(s) unless the registered holder(s) is/are completing the
               Special Issuance Instructions.

          (e)  If the certificates of the Mission Common Stock and the Cash
               Consideration are to be issued and paid in the name of a person
               other than the signer of a Letter of Transmittal, then
               certificates representing the shares of Bargo Common Stock
               surrendered in exchange therefor must be endorsed or accompanied
               by an appropriate instrument of transfer signed exactly as the
               name of the registered owner appears on such certificates, with
               the signatures on the certificates or instruments of transfer
               guaranteed by an Eligible Institution (unless signed by an
               Eligible Institution).

          (f)  If this Letter of Transmittal or any Certificate, proxy or stock
               power is signed by a trustee, executor, administrator, guardian,
               attorney-in-fact, officer of a corporation or other person
               acting in a fiduciary or representative capacity, such person
               must so indicate when signing, and proper evidence satisfactory
               to Mission Resources of their authority to so act must be
               submitted.

          (g)  If this Letter of Transmittal is signed by a person other than
               the registered holder(s) of the shares of Bargo Common Stock
               listed, the Certificate must be endorsed or accompanied by
               appropriate stock powers, in either case signed exactly as the
               name(s) of the registered holder(s) appear(s) on the
               Certificates. Signatures on such Certificates or stock powers
               must be guaranteed by an Eligible Institution (unless signed by
               an Eligible Institution).

         5. Withholding. The Exchange Agent and Mission Resources are entitled
to deduct and withhold from the consideration otherwise payable pursuant to the
Merger described in the Prospectus to any holder of shares of Bargo Common Stock
any amounts that the Exchange Agent or Mission Resources, as the case may be, is
required to deduct and withhold with respect to the making of such payment
under the Internal Revenue Code of 1986 (the "CODE"), or any provision of state,
local or foreign tax law. To the extent that amounts are withheld, the withheld
amounts shall be treated for all purposes as having been paid to the holder of
shares of Bargo Common Stock in respect of which such deduction and withholding
was made.

         6. Special Issuance and Special Delivery Instructions. If the
Mission Common Stock and the Cash Consideration are to be issued and paid to
someone other than the holder or mailed to an address other than that shown
above, the appropriate boxes on this Letter of Transmittal should be completed.

         7. Irregularities. All questions as to the form of documents and the
validity of shares of Bargo Common Stock will be resolved by Mission Resources,
in its sole discretion, whose determination shall be final and binding. Mission
Resources reserves the absolute right to reject any deliveries of any
Certificates for exchange that are not in proper form, or the acceptance of
which would, in the opinion of Mission Resources or its counsel, be unlawful.
Mission Resources reserves the absolute right to waive any defect or
irregularity of delivery for exchange with regard to any shares of Bargo Common
Stock.

         8. Mutilated, Lost, Stolen or Destroyed Certificates. Any holder whose
Certificate(s) have been mutilated, lost, stolen or destroyed should complete
this Letter of Transmittal and attach a letter to it indicating that his/her
Certificate(s) has/have been mutilated, lost, stolen or destroyed and mail or
otherwise deliver both to the Exchange Agent at the address set forth on the
front of this Letter of

<PAGE>   6

Transmittal. The holder will then be instructed as to the steps he/she must take
in order to receive the Certificate(s) representing the Mission Common Stock.

         9. Requests for Assistance or Additional Copies. Requests for
assistance or for additional copies of this Letter of Transmittal may be
directed to the Exchange Agent at one of the addresses or telephone numbers set
forth on the cover of this Letter of Transmittal.

                            IMPORTANT TAX INFORMATION

         Under federal income tax law, a holder who delivers shares of Bargo
Common Stock for exchange is required to provide Mission Resources (as payer),
through the Exchange Agent, with the holder's correct taxpayer identification
number ("TIN") on Substitute Form W-9 or otherwise establish a basis for
exemption from backup withholding. Generally, if the holder is an individual,
the TIN is the holder's social security number. If the Exchange Agent is not
provided with the correct taxpayer identification number, the holder may be
subject to a $50 penalty, as well as various other penalties, imposed by the
Internal Revenue Service. In addition, payments made to the holder with respect
to the Mission Common Stock or the Bargo Common Stock may be subject to backup
withholding.

         Certain holders (including, among others, all corporations and certain
foreign individuals) are not subject to these backup withholding and reporting
requirements. Exempt holders should indicate their exempt status on Substitute
Form W-9. A foreign individual may qualify as an exempt recipient or other
payee by submitting to the Exchange Agent a properly completed Internal Revenue
Service Form W-8 signed under penalty of perjury, attesting to the holder's
exempt status.

         If backup withholding applies, Mission Resources is required to
withhold 31% of any payment made to the holder or other payee. Backup
withholding is not an additional federal income tax. Rather, the amount
withheld will be credited against the federal income tax liability of persons
subject to backup withholding. If withholding results in an overpayment of
taxes, a refund may be obtained from the Internal Revenue Service provided that
the required information is timely furnished to the Internal Revenue Service.

PURPOSE OF SUBSTITUTE FORM W-9

         To prevent backup withholding on payments that are made to a holder
with respect to the Mission Common Stock or the Bargo Common Stock, the holder
is required to provide the Exchange Agent with either: (i) the holder's correct
TIN by completing the form below, certifying that the TIN provided on Substitute
Form W-9 is correct (or that the holder is awaiting a TIN) and that (A) the
holder has not been notified by the Internal Revenue Service that he or she is
subject to backup withholding as a result of failure to report all interest or
dividends or (B) the Internal Revenue Service has notified the holder that he or
she is no longer subject to backup withholding; or (ii) an adequate basis for
exemption.

WHAT NUMBER TO GIVE THE EXCHANGE AGENT

         The holder is required to give the Exchange Agent the TIN (e.g., social
security number or employer identification number) of the record owner of the
Bargo Common Stock.

<PAGE>   7

              TO BE COMPLETED BY ALL HOLDERS OF BARGO COMMON STOCK
        (See Instruction 5 and "Important Tax Information" on this Letter
                                of Transmittal)

<TABLE>
<CAPTION>

                   PAYER'S NAME: MISSION RESOURCES CORPORATION

<S>                                     <C>                             <C>
       SUBSTITUTE                       Part I--PLEASE PROVIDE YOUR         Social Security Number
        FORM W-9                        TIN IN THE BOX AT RIGHT AND
Department of the Treasury              CERTIFY BY SIGNING AND                -----------------
 Internal Revenue Service               DATING BELOW.                              -----
                                                                                     OR
                                                                        Employer Identification Number

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

 Payer's Request for Taxpayer           Name (Please Print)
Identification Number (TIN) and                             -------------------------------
      Certificate                       Address
                                                -------------------------------------------

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

                                        ---------------------------------------------------
                                        City              State                    ZIP Code

                                        Part 2--Awaiting TIN  [ ]

Part 3--CERTIFICATION--UNDER THE PENALTIES OF PERJURY, I CERTIFY THAT (1) the
number shown on this form is my correct taxpayer identification number (or a TIN
has not been issued to me but I have mailed or delivered an application to
receive a TIN or intend to do so in the near future), (2) I am not subject to
backup withholding either because I have not been notified by the Internal
Revenue Service (the "IRS") that I am subject to backup withholding as a result
of a failure to report all interest or dividends or the IRS has notified me that
I am no longer subject to backup withholding, and (3) all other information
provided on this form is true, correct and complete.

Signature                                    Date
          --------------------------------        ------------------------------

You must cross out item (2) above if you have been notified by the IRS that you
are currently subject to backup withholding because of under-reported interest
or dividends on your tax return and you have not been advised by the IRS that
such backup withholding has been terminated.
</TABLE>

   FAILURE TO COMPLETE AND RETURN THIS FORM MAY RESULT IN BACKUP WITHHOLDING.

               YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU
                CHECKED THE BOX IN PART 2 OF SUBSTITUTE FORM W-9

<PAGE>   8

             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER

I certify under the penalties of perjury that a taxpayer identification number
has not been issued to me, and either (a) I have mailed or delivered an
application to receive a taxpayer identification number to the appropriate
Internal Revenue Service Center or Social Security Administration Office or (b)
I intend to mail or deliver an application in the near future. I understand that
if I do not provide a taxpayer identification number within sixty (60) days,
31% of all reportable payments made to me thereafter will be withheld until I
provide a number.

Signature                                            Date
         ------------------------------------------      -----------------------<PAGE>   1
                                                                     Exhibit 4.3

                                SIPEX CORPORATION

                      2000 NON-QUALIFIED STOCK OPTION PLAN

           1. PURPOSE. This 2000 Non-Qualified Stock Option Plan (the "Plan") is
intended to provide incentives to non-officer employees and consultants of SIPEX
Corporation (the "Company"), and of any present or future parent or subsidiary
of the Company ("Related Entities") by providing them with opportunities to
purchase stock in the Company pursuant to options ("Non-Qualified Options" or
"Options") granted hereunder which do not qualify as "incentive stock options"
("ISOs") under Section 422(b) of the Internal Revenue Code (the "Code"). No
Options may be granted pursuant to this Plan to any officer or director of the
Company or any Related Entity. 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. For purposes of this
Plan, the term "officer" shall be interpreted in accordance with the
interpretations of the National Association of Securities Dealers, Inc. ("NASD")
under the NASD Marketplace Rules.

           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, subject to paragraph 2(C) (relating to compliance with Section
           162(m) of the Code), by a committee appointed by the Board (the
           "Committee"). 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 Option
           by the Board, and subject to the terms of the Plan, the Committee
           shall have the authority to (i) determine to whom, from among the
           class of individuals and entities eligible under paragraph 3 to
           receive Options, Options may be granted; (ii) determine the time or
           times at which Options shall be granted; (iii) determine the option
           price of shares subject to each Option, which price shall not be less
           than the minimum price specified in paragraph 6; (iv) determine
           (subject to paragraph 7) the time or times when each Option shall
           become exercisable and the duration of the exercise period; (v)
           determine whether restrictions such as repurchase options are to be
           imposed on shares subject to Options and the nature of such
           restrictions, if any, and (vi) interpret the Plan and prescribe and
           rescind rules and regulations relating to it. The Committee shall
           take whatever actions it deems necessary, under Section 422 of the
           Code and the regulations promulgated thereunder, to ensure that no
           Option issued hereunder is treated as an ISO. The interpretation and
           construction by the Committee of any provisions of the Plan or of any
           Option 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
<PAGE>   2
           Committee shall be liable for any action or determination made in
           good faith with respect to the Plan or any Option 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 by a majority of the members of the
           Committee, or acts reduced to or approved in writing by a majority of
           the members of the Committee (if consistent with applicable state
           law), shall constitute 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. PERFORMANCE-BASED COMPENSATION. The Board, in its
           discretion, may take such action as may be necessary to ensure that
           Options granted under the Plan qualify as "qualified
           performance-based compensation" within the meaning of Section 162(m)
           of the Code and applicable regulations promulgated thereunder
           ("Performance-Based Compensation"). Such action may include, in the
           Board's discretion, some or all of the following (i) if the Board
           determines that Options granted under the Plan generally shall
           constitute Performance-Based Compensation, the Plan shall be
           administered, to the extent required for such Options to constitute
           Performance-Based Compensation, by a Committee consisting solely of
           two or more "outside directors" (as defined in applicable regulations
           promulgated under Section 162(m) of the Code), (ii) if any
           Non-Qualified Options with an exercise price less than the fair
           market value per share of Common Stock are granted under the Plan and
           the Board determines that such Options should constitute
           Performance-Based Compensation, such options shall be made
           exercisable only upon the attainment of a pre-established, objective
           performance goal established by the Committee, and such grant shall
           be submitted for, and shall be contingent upon shareholder approval
           and (iii) Options granted under the Plan may be subject to such other
           terms and conditions as are necessary for compensation recognized in
           connection with the exercise or disposition of such Option or the
           disposition of Common Stock acquired pursuant to such Option, to
           constitute Performance-Based Compensation.

           3. ELIGIBLE EMPLOYEES AND OTHERS. Non-Qualified Options may be
granted to any non-officer employee or consultant of the Company or any Related
Entity. The Committee may take into consideration a recipient's individual
circumstances in determining whether to grant an Option. The granting of any
Option to any individual or entity shall neither entitle such grantee to, nor
disqualify such grantee from, participation in any other grant of Options.

           4. STOCK. The stock subject to Options 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 1,000,000, subject to adjustment as provided in paragraph 13. If any Option
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
<PAGE>   3
in part or shall be repurchased by the Company, the shares of Common Stock
subject to such Option shall again be available for grants of Options under the
Plan.

           No employee or consultant of the Company or any Related Entity may be
granted Options to acquire, in the aggregate, more than 700,000 shares of Common
Stock under the Plan, subject to adjustment as provided in Paragraph 13. If any
Option 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 Option shall be included in the determination of the
aggregate number of shares of Common Stock deemed to have been granted to such
employee or consultant under the Plan.

           5. GRANTING OF OPTIONS. Options may be granted under the Plan at any
time on or after October 31, 2000 and prior to October 31, 2010. The date of
grant of an Option under the Plan will be the date specified by the Committee at
the time it grants the Option; 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.

           Subject to paragraph 2(C) (relating to compliance with Section 162(m)
of the Code), the exercise price per share specified in the agreement relating
to each Non-Qualified Option granted under the Plan (the "Agreement"), may not
be less than the fair market value of the Common Stock on the date of grant, but
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.

           7. OPTION DURATION. Subject to earlier termination as provided in
other provisions of this Plan or as specified in the Agreement relating to such
Option, each Option shall expire on the date specified by the Committee, but not
more than ten years from the date of grant.

           8. EXERCISE OF OPTION. Subject to the other provisions of this Plan,
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.
<PAGE>   4
                      D. ACCELERATION OF VESTING. The Committee shall have the
           right to accelerate the date that any installment of any Option
           becomes exercisable despite the fact that the foregoing action may
           cause the application of Sections 280G and 4999 of the Code if a
           change in control of the Company occurs.

           9. TERMINATION OF BUSINESS RELATIONSHIP. Each Option may provide that
it shall terminate before its stated expiration date, upon terms specified by
the Committee, if the optionee ceases to be an employee or consultant of the
Company, or of any Related Entity (any such relationship hereinafter referred to
as a "Business Relationship with the Company"). Nothing in the Plan or any
Option granted hereunder shall be deemed to give any optionee the right to
continue his or her Business Relationship with the Company for any period of
time. For purposes of this paragraph 9, a Business Relationship 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 or by contract. A bona fide leave of absence with the
written approval of the Committee shall not be considered an interruption of a
Business Relationship under this paragraph 9, provided that such written
approval contractually obligates the Company or any Related Entity to continue
the Business Relationship of the optionee after the approved period of absence.
In the event of such an approved leave of absence, vesting shall be suspended
(and the period of the leave of absence shall be added to all vesting dates)
unless otherwise agreed upon.

           10. DEATH; DISABILITY.

                      A. DEATH. Unless otherwise specified by the Committee, if
           an optionee's Business Relationship with the Company terminates by
           reason of death, his or her Option may be exercised, to the extent of
           the number of shares with respect to which such optionee could have
           exercised it on the date of such optionee's death, by such optionee's
           estate, personal representative or beneficiary who has acquired the
           Option by will or by the laws of descent and distribution, at any
           time prior to the earlier of the specified expiration date of the
           Option or 180 days from the date of death.

                      B. DISABILITY. Unless otherwise specified by the
           Committee, if an optionee's Business Relationship with the Company
           terminates by reason of such optionee's disability, such optionee
           shall have the right to exercise his or her Option, to the extent of
           the number of shares with respect to which such optionee could
           otherwise have exercised it on the date his or her Business
           Relationship with the Company terminated, at any time prior to the
           earlier of the specified expiration date of the Option or 180 days
           from the date of the termination of the optionee's Business
           Relationship with the Company. 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. Options shall be assignable or transferable only
to the extent provided in the agreement relating to such option.
<PAGE>   5
           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 Option
shall be subject to the restrictions set forth herein or, consistent with
paragraph 7, to such other or additional 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 or other
           reorganization in which the holders of the outstanding voting stock
           of the Company immediately preceding the consummation of such event,
           shall, immediately following such event, hold, as a group, less than
           a majority of the voting securities of the surviving or successor
           entity, or in the event of a sale of all or substantially all of the
           Company's assets or otherwise (other than a spin-off or similar
           transaction), or in the event of any other acquisition of the
           business of the Company, or determined by the Board (each, 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, 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 or successor
           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 or to be exercisable as a
           result of the Acquisition, within a specified number of days of the
           date of
<PAGE>   6
           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 or to be exercisable as a
           result of the Acquisition) 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 such optionee would have
           received if such optionee had exercised his or her Option prior to
           such recapitalization or reorganization.

                      D. DISSOLUTION OR LIQUIDATION. In the event of the
           proposed dissolution or liquidation of the Company, then the
           Committee shall, as to outstanding Options, at its discretion
           provide, upon written notice to the optionees, (i) 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 (ii) that such Options
           (including those which have not yet vested) shall be exercisable
           within a specified number of days of such notice, at the end of which
           period the Options shall terminate.

                      E. 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.

                      F. 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.

                      G. ADJUSTMENTS. Upon the happening of any of the events
           described in subparagraphs A, B or C above, the class and aggregate
           numbers of shares set forth in paragraph 4 hereof that are subject to
           Options 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.

           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
<PAGE>   7
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 optionee'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.
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
October 31, 2000. The Plan shall expire at the end of the day on October 31,
2010 (except as to Options outstanding on that date). The Board may terminate or
amend the Plan in any respect at any time.

           16. REPRICING. Without the prior approval of the Company's
stockholders, Options issued under the Plan will not be repriced, replaced or
regranted through cancellation or by lowering the Option exercise price of a
previously granted Option.

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

           18. WITHHOLDING OF ADDITIONAL INCOME TAXES. Each optionee shall pay
to the Company, or make provisions satisfactory to the Company for payment of,
any taxes required by law to be withheld in connection with Options to such
optionee no later than the date of the event creating the tax liability. The
Board may allow optionees to satisfy such tax obligations in whole or in part by
transferring shares of Common Stock, including shares retained from the Option
creating the tax obligation, valued at their fair market value (as determined by
the Board or as determined pursuant to the applicable Agreement). The Company
may, to the extent permitted by law, deduct any such tax obligations from any
payment of any kind otherwise due to an optionee.

           19. DETERMINATION OF FAIR MARKET VALUE OF COMMON STOCK. Whenever,
under the terms of any option agreement or in administering the Plan, it is
necessary or desirable to determine the fair market value of the Company's
Common Stock, the Committee shall make such determination in accordance with
this paragraph. "Fair Market Value" shall be determined as of the last business
day for which the prices or quotes discussed in this sentence are available
prior to the date such Option is granted 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
<PAGE>   8
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.
However, if the Common Stock is not publicly traded at the time an Option is
granted under the Plan, "fair market value" shall be deemed to be 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.

           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 or Related Entities with respect to the Plan. For example, the
Company may be required to file tax information returns reporting the income
received by optionees 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 Massachusetts,
or the laws of any jurisdiction in which the Company or its successors in
interest may be organized.

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