Document:

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                                                                Exhibit 10.16

                                                                       1/4/00

                                      LEASE

                                 By and Between

                        1050 HINGHAM STREET REALTY TRUST
                                    Landlord

                                       and

                                 BIOSPHERE, INC.
                                     Tenant

                               1050 HINGHAM STREET
                             ROCKLAND, MASSACHUSETTS
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                                 REFERENCE DATA

As used in this Lease, the following terms shall have the respective meaning set
forth below except when and to the extent reference is made to particular
Sections of the Lease:

Date of Lease:         January 7, 2000

Landlord:              Thomas J. Teuten and John H. Spurr, Jr., Trustees of 1050
                       Hingham Street Realty Trust

Landlord's Address:    20 Winthrop Square, Boston, Massachusetts 02110-1229.

Tenant:                BioSphere, Inc., a Delaware corporation.

Tenant's Address:      111 Locke Drive, Marlboro, Massachusetts 01757

Property:              Landlord's land and improvements thereon known as 1050
                       Hingham Street, Rockland, Massachusetts 02370.

Building:              The three-story building located on the Property.

Leased Premises:       A portion of the first (1st) floor of the Building as
                       shown on Exhibit A.

Rentable Square
Footage of the Leased
Premises:              7,797 square feet to be certified by Landlord's
                       Architect.

Total Rentable
Square Footage of the
Building:              39,771 square feet.

Use of Leased
Premises:              Administrative offices for a medical device company and
                       ancillary uses related thereto including research and
                       development and light manufacturing to the extent
                       described in Exhibit D attached hereto and incorporated
                       herein, provided that such research and development
                       involve no hazardous materials, solid waste, noise or
                       fumes beyond the Leased Premises or any impact on the
                       Building, its operations or the operations of other
                       tenants in the Building.

Lease Term:            Five (5) years.

Specified Commencement
Date:                  March 15, 2000.

      Landlord's Initials________                 Tenant's Initials_________

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Commencement Date:     The Specified Commencement Date or such other date as
                       determined in accordance with the terms of Section 3.

Base Rent:             Lease         Annual            Monthly
                       Year        Base Rent         Installment
                       -----       ---------         -----------
                       1 - 3       $155,940.00       $12,995.00
                       4 & 5       $161,787.75       $13,482.31

Lease Security:        An irrevocable letter of credit (the "Letter of Credit")
                       or cash Security Deposit of $140,000, to be reduced as
                       scheduled below, subject to Section 4.

                       Lease Year           Amount
                       ----------           ------
                           1              $140,000
                           2               115,500
                           3                92,400
                           4                64,400
                           5                33,600

Base Operating Costs:  Operating costs for the calendar year 2000, grossed up to
                       reflect 100% occupancy for a full calendar year.

Base Taxes:            Taxes for the fiscal year ended June 30, 1999.

Electricity:           $6,627.45 per year or $552.29 per month.

Tenant's Proportionate
Share:                 19.605%

Broker:                Meredith & Grew, Incorporated.

Insurance:             $1,000,000/$3,000,000 per occurrence public liability;
                       $1,000,000 per occurrence property damage.
                       Personal Property  insurance for all risks to full
                       insurable value of personalty in the Leased Premises.

Landlord's Initial
Construction:          Landlord shall provide a buildout subject to the
                       conditions of Schedule A and Tenant Construction
                       Contribution of up to $31,188 toward the cost of design
                       and construction of Landlord's Initial Construction to
                       the extent such cost exceeds $140,346.

      Landlord's Initials________                 Tenant's Initials_________

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                               TABLE OF CONTENTS
                               -----------------
                                                             Page
                                                             ----

            1.    Leased Premises.............................1

            2.    Use.........................................1

            3.    Lease Term..................................2

            4.    Base Rent, Security Deposit.................2

            5.    Operating Cost Escalation...................3

            6.    Tax Escalation..............................5

            7.    Building and Equipment......................7

            8.    Property of Tenant..........................8

            9.    Services....................................8

            10.   Removal of Goods and Tenant's Repairs.......9

            11.   Improvements, Alterations and Ownership.....9

            12.   Inspection.................................11

            13.   Casualty...................................11

            14.   Condemnation - Eminent Domain..............13

            15.   Indemnification............................14

            16.   Liability Insurance........................15

            17.   Damage to Property of Tenant...............15

            18.   Injury and Damage..........................15

            19.   Waiver of Subrogation......................15

            20.   Assignment, Mortgaging and Subletting......16

            21.   Signs and Drapes...........................18

            22.   Landlord's Insurance.......................18

            23.   Inflammables, Odors........................18

            24.   Default....................................18

            25.   Subordination..............................20

            26.   Holdover...................................21

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                               TABLE OF CONTENTS
                               -----------------
                                                             Page
                                                             ----

            27.   Notices....................................21

            28.   Rules and Regulations......................22

            29.   Quiet Enjoyment............................22

            30.   Disputes; Landlord's Reasonableness;
                  Arbitration................................22

            31.   Seisin.....................................22

            32.   Binding Agreement..........................22

            33.   Notice of Lease............................23

            34.   Landlord's Right to Cure...................23

            35.   Hazardous Materials........................23

            36.   First Offer for Basement Space.............23

            37.   General Provisions.........................24

                  Exhibit A1 - Lease Plan
                  Exhibit A2 - Site Plan
                  Exhibit B - Rules and Regulations
                  Exhibit C - Cleaning Specifications
                  Exhibit D - Clarification of Light Manufacturing Use

                  Schedule A - Landlord's Initial Construction
                  Schedule B - Building Standard

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This Lease is made and entered into as of the Date of Lease by and between
Landlord and Tenant (both defined in the Reference Data section) on the
following terms and conditions which the Landlord and Tenant covenant and agree
to keep and perform.

l. Leased Premises. In consideration of the rents and covenants herein
stipulated to be paid and performed by Tenant and upon the terms and conditions
herein specified, Landlord hereby leases to Tenant, and Tenant hereby hires and
takes from Landlord, the Leased Premises (as defined in the Reference Data
section) as indicated by outlining and diagonal marking on the plan labeled
Exhibit A1 which is attached hereto and incorporated herein, excluding elevator
shafts, stairs and other common elements of the Building, on the terms
hereinafter stated, which Leased Premises are hereby agreed to contain the
Rentable Square Footage of the Leased Premises (as defined in the Reference Data
section). The Tenant shall have the right to use in common with others the
elevators, stairs and entrances and exits of the Building and the grounds of the
Property, including the walkways and parking areas as shown in Exhibit A2. At
the present time there are approximately 250 parking spaces. Landlord shall
maintain available for use of Tenants in the Building and their visitors, a
minimum of four (4) parking spaces per 1,000 r.s.f. of total office and basement
area (49,208 r.s.f.) except for reasonable interruption for repairs or
improvements of the parking lot. Landlord reserves the right, on reasonable
notice and at no additional capital cost to Tenant, to change the traffic
patterns on the Property, including without limitation the access to and egress
from the Property, if Landlord reasonably determines that such change will
improve traffic conditions on the Property or adjacent roads.

2. Use. Tenant may use the Leased Premises only for the Use of Leased Premises
(defined in the Reference Data section). Such use and occupation shall at all
times be in compliance with the ordinances of the Town of Rockland, the laws of
The Commonwealth of Massachusetts and the United States of America and any
regulations under any thereof. Tenant shall not use, permit or suffer anything
to be done in the Leased Premises or anything to be brought into or kept in the
Leased Premises, in either case, which occasions undue hazard, discomfort or
annoyance to any other tenants or occupants of the Building, or which in
Landlord's reasonable judgment may tend to impair the reputation or appearance
of the Building and tend to interfere with the proper and economic operation of
the Building by Landlord. Tenant agrees that, except as set forth in the
following sentence for "Kitchen Areas," it shall not use the Leased Premises or
any part thereof, or permit the Leased Premises or any part thereof to be used,
for the preparation or dispensing of food, whether by vending machines or
otherwise. Notwithstanding the preceding sentence of this Section, but subject
to the other terms and conditions of this Section and this Lease, Tenant may
install at its own expense so-called hot-cold water fountains, coffee makers,
beverage vending machines, microwave ovens, refrigerators and sinks ("Kitchen
Areas") for the heating and consumption of food on the Leased Premises by
Tenant's employees only, provided that no cooking, frying, etc. are carried on
in the Leased Premises to such extent as creates odors of any kind beyond the
Kitchen Areas or requires special exhaust venting, and provided further that the
installation and operation of such Kitchen Areas shall not result in any
increase in Landlord's insurance premiums or costs unless such increase is fully
paid for, in advance, by Tenant. Tenant hereby acknowledges that the Building is
not engineered to provide any such special venting.

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3. Lease Term. Subject to the terms, covenants, agreements and conditions
contained herein, Tenant shall have and hold the Leased Premises for the Lease
Term (defined in the Reference Data section), commencing on the Commencement
Date and terminating on the last day of the month in which the date immediately
preceding the applicable anniversary of the "Commencement Date" shall occur (the
"Expiration Date"), unless sooner terminated pursuant to any of the terms and
conditions of this Lease or pursuant to law. The "Commencement Date" shall be
the later to occur of (i) the Specified Commencement Date (defined in the
Reference Data section) or (ii) the date on which Landlord's Initial
Construction (defined in Section 11(a)) is Substantially Complete (as defined in
Schedule A), and in any event on the date on which Tenant occupies any portion
of the Leased Premises for its business purposes, which shall not include entry
for purposes of preparing the Leased Premises for occupancy. In the event
Landlord fails to deliver the Leased Premises to Tenant with the Landlord's
Initial Construction Substantially Completed on or prior to June 24, 2000 then
Tenant may cancel this Lease, without further liability of Tenant to Landlord
upon seven (7) days written notice from Tenant to Landlord; provided however,
that if, within two (2) business days after receipt of such notice, Landlord
provides evidence reasonably satisfactory to Tenant that the Leased Premises
shall be available for occupancy in accordance with this Lease prior to July 15,
2000, then Tenant agrees to revoke such termination as long as the Leased
Premises are so delivered.

After the beginning of the Lease Term, Landlord and Tenant shall, upon the
request of either, execute a letter agreement or other acknowledgment specifying
the dates on which the Lease Term begins and ends.

4. Base Rent; Security Deposit:

      (a) Tenant covenants to pay to Landlord during and through the Lease Term,
      inclusive, annual "Base Rent" equal to the amounts specified in the
      Reference Data section.

      Such annual rent is payable in equal monthly installments, in advance, on
      the first day of every calendar month during the Lease Term hereof, and a
      proportionate part of such monthly installment is payable for any fraction
      of a calendar month occurring at the beginning or end of the Lease Term
      (such annual rent is hereinafter called the "Base Rent"). Tenant will pay
      the Base Rent without notice, demand or deduction, except as specified
      above, to the Landlord at Landlord's Address (defined in the Reference
      Data section), or at such other place as is designated from time to time
      by notice from Landlord to Tenant.

      (b) Upon execution of this lease, Tenant shall pay to Landlord a security
      deposit, the "Security Deposit", (or in lieu thereof, a letter of credit
      as provided below) specified in the Reference Data section as "Lease
      Security", which shall be held as security for the Tenant's performance as
      herein provided and refunded to the Tenant at the end of this Lease,
      subject to Tenant's satisfactory compliance with the conditions hereof.
      The Security Deposit shall be kept in a separate interest bearing bank
      account subject to withdrawal by Landlord under the terms and conditions
      provided below. Provided Tenant is not in default hereunder, Landlord
      shall pay any interest accrued and posted to the account to Tenant on or
      before July 31 and December 31 of each calendar year during the Lease
      Term. Tenant shall be responsible for all taxes, fees, charges or other
      expenses associated with such account. At Tenant's option, on

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      one occasion during the Lease Term, Tenant may substitute for the Security
      Deposit a letter of credit (the "Letter of Credit"). Such Letter of Credit
      shall be irrevocable and issued by a banking institution and in a form
      reasonably acceptable to Landlord. If the Letter of Credit is issued for a
      term shorter than the remainder of the Lease Term, Tenant shall provide
      Landlord with a renewal Letter of Credit no later than thirty (30) days
      prior to the expiration of such Letter of Credit. If all or any part of
      the Lease Security shall be applied to any obligation of Tenant under the
      Lease, Tenant shall immediately upon request by Landlord restore the Lease
      Security to it's original amount. Provided Tenant has not been in default
      of any of the terms of this Lease prior to or at the time of any scheduled
      reduction, the amount of the Lease Security shall be reduced on the first
      day after the Lease Year specified to the amount specified in the
      Reference Data section. Tenant shall not have the right to call upon
      Landlord to apply all or any part of the Lease Security to cure any
      default or fulfill any obligation of Tenant, and such use shall be solely
      in the description of Landlord.

5. Operating Cost Escalation. As used in this Section 5, these words and terms
shall have the following meanings:

      (a) "Operating Costs" shall mean all costs incurred and expenditures made
      by the Landlord in the operation and management of the Building and the
      Property, exclusive of financing expenses and real estate taxes, as
      determined in accordance with generally accepted accounting principles.
      Operating Costs include, without limitation, costs of janitorial service,
      heating, electricity and air-conditioning (except to the extent payable
      directly by Tenant as set forth in Section 9 below); maintenance and
      repairs to the Building (except for the obligations of Tenant within the
      Leased Premises) and the Building HVAC systems and equipment, supplies,
      maintenance of the parking areas and grounds, snow removal, management
      fees, wages, salaries, benefits, payroll taxes and unemployment
      compensation insurance for employees of Landlord, and all the costs for
      the cleaning, operation, maintenance or security of the Property;
      insurance relating to the Property; legal fees related to the management
      of tenants and operation of the Property (except for the negotiation of
      Leases and otherwise to the extent such legal fees are charged to
      individual tenants) payments other than Taxes (as hereinafter defined) to
      the Town of Rockland including, but not limited to, water and sewer
      charges; amortization of capital expenditures, including the cost of money
      connected therewith, which result in reduction of the increase or rate of
      increase in operating expenses; and all other expenses customarily
      incurred in connection with the operation of first class office buildings.
      Operating costs shall not include:

1)    cost of alterations of Tenant space;
2)    depreciation, interest and principal payments on mortgages, and other debt
      costs; if any;
3)    real estate broker's leasing and brokerage commissions or compensations
      and advertising and other marketing expenses;
4)    costs of special services provided to some; but not substantially all of
      the tenants of the Building;
5)    rental under any ground or underlying lease or leases;
6)    wages, salaries or other compensation paid to employees above the level of
      Building Manager;

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7)    any expenditures of which Landlord has been or will be reimbursed (other
      than pursuant to rent adjustment, escalation or general expense
      reimbursement in leases), including insurance and condemnation proceeds,
      services contracts and warranties;
8)    the cost of correcting defects in the construction of the Building (latent
      or otherwise), provided that the foregoing shall not exclude the costs of
      normal repair, maintenance and replacement;
9)    any compensation paid to clerks, attendants or other persons in commercial
      concessions operated by Landlord; if any;
10)   accounting fees to the extent not specifically related to the operation of
      the Building;
11)   any fees and expenses paid to an agent, contractor or manager which is
      related to Landlord to the extent such fees or expenses are in excess of
      the customary market amounts which would be paid in the absence of such
      relationship;
12)   expenses for repairs or the work occasioned by condemnation or by a
      casualty except amount below the deductible of any insurance policy
      carried by Landlord on the Building, provided such deductible does not
      exceed $10,000;
13)   fines and penalties for violation of governmental laws, regulatory orders
      or conditions;
14)   environmental compliance or remediation to the extent considered
      acceptable cost under GAAP;
15)   capital expenditures, except as specified above; and

16)   reserves for future capital expenditures.

      If the Building shall not have been fully occupied during any portion of a
      year for which Operating Costs are being computed, Operating Costs for
      such year or portion thereof shall be reasonably projected by Landlord to
      the estimated Operating Costs that would have been incurred if the
      Building had been fully occupied for such year, and such projected amount
      shall be deemed to be the Operating Costs for such year.

      (b) "Operating Escalation Statement" shall mean a statement in writing
      signed by Landlord, setting forth the amounts payable by Tenant for a
      specified computation year pursuant to this Section.

      (c) "Tenant's Proportionate Share" shall mean that percentage defined in
      the Reference Data section which is a fraction, the numerator of which is
      the Rentable Square Footage of the Leased Premises and the denominator of
      which is the Total Rentable Square footage of the Building (both as
      defined in the Reference Data section).

      Operating Costs Excess: If in any calendar year occurring during the Lease
      Term, the Operating Costs for such year exceed the Base Operating Costs
      (as defined in the Reference Data section), the Tenant shall pay to the
      Landlord as additional rent an amount (hereinafter called the "Operating
      Costs Excess") equal to the Tenant's Proportionate Share of any such
      excess. Beginning with the first installment of Base Rent, and continuing
      thereafter during the Lease Term, Tenant shall pay to Landlord on the
      first day of each calendar month one-twelfth (1/12) of the sum equal to
      Landlord's reasonable estimate of Operating Costs Excess for such calendar
      year, and such payments shall be credited to the Operating Costs Excess,
      if any, payable for the current calendar year. After the end of each
      calendar year, Landlord shall give

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      to Tenant the Operating Escalation Statement which shall show the actual
      Operating Costs Excess together with the total of estimated payments
      applied. Any balance due Landlord shall be payable by Tenant thirty (30)
      days following receipt by Tenant of the Operating Cost Escalation
      Statement, with any excess estimated payments credited by Landlord to
      Tenant against the Rent next due hereunder, provided that any excess
      credit shall be repaid to Tenant within ninety (90) days following the end
      of the calendar year in which occurs the expiration of the Lease Term,
      subject to set off against sums due from Tenant to Landlord.

      Part Years: If this Lease shall commence or terminate in the middle of a
      computation year, Tenant shall be liable for only that portion of the
      Operating Costs Excess in respect of such computation year represented by
      a fraction the numerator of which is the number of days of the Lease Term
      which falls within the computation year and the denominator of which is
      three hundred sixty-five (365).

      Data: Upon request made within thirty (30) days of receipt of any
      Operating Escalation Statement, Landlord shall promptly provide to Tenant
      reasonable data to permit Tenant to verify the Operating Costs contained
      therein, but Tenant may not dispute any such element of cost or expenses
      not objected to within thirty (30) days of receipt of such data. Any
      obligation of Tenant under this Section 5 which shall not have been paid
      at the expiration of the Lease Term shall survive such expiration and
      shall be paid when and as the amount of same shall be determined together
      with interest thereon at the Lease Interest Rate (defined in Section 24)
      from the date the Operating Cost Excess was first due to Landlord.

6. Tax Escalation: As used in this Section 6, these words and terms shall have
the following meanings:

      (a) "Taxes" shall mean all real estate tax payments to the Town of
      Rockland or payments in lieu of thereof, all taxes, assessments and
      betterments levied, assessed or imposed by any governmental authority upon
      or against the Building and the Property or payments in lieu thereof, but
      excluding water and sewer charges. If, at any time during the Lease Term,
      any tax or excise on rents or other taxes, however described, are levied
      or assessed against Landlord with respect to the rent reserved hereunder,
      either wholly or partially in substitution for, or in addition to, real
      estate taxes assessed or levied on the Property, or payments in lieu
      thereof, such tax or excise on rents shall be included in Taxes; however,
      Taxes shall not include franchise, estate, inheritance, succession,
      capital levy, transfer, income or excess profits taxes assessed on
      Landlord.

      (b) "Tax Escalation Statement" shall mean a statement in writing signed by
      Landlord, setting forth the amounts payable by Tenant for a specified
      computation year pursuant to this Section.

      Tax Excess: If in any real estate tax fiscal year occurring during the
      Lease Term, the Taxes for such year exceed the Base Taxes (as defined in
      the Reference Data section), the Tenant shall pay to the Landlord as
      additional rent an amount (hereinafter called the "Tax Excess") equal to
      the Tenant's Proportionate Share of any such excess. Beginning with the
      first installment of Base Rent, and continuing thereafter during the Lease
      Term, Tenant shall pay to Landlord

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      on the first day of each calendar month one-twelfth (1/12) of the sum
      equal to Landlord's reasonable estimate of the Tax Excess for such fiscal
      year, and such payments shall be credited to the Tax Excess, if any,
      payable for the applicable fiscal year. Such estimated payments shall be
      timed so that Landlord has the amounts available on the due dates for tax
      bills in the Town of Rockland. During the fiscal year, Landlord shall give
      to Tenant Tax Escalation Statement(s) based upon tax bills received from
      time to time from the Town of Rockland, showing the Tax Excess together
      with the total of estimated payments applied. Any balance due Landlord
      shall be payable by Tenant thirty (30) days following receipt by Tenant of
      each Tax Escalation Statement. Any excess estimated payments shall be
      carried to the credit of Tenant until the issuance of the last such Tax
      Escalation Statement for each fiscal year and if the statement indicates
      an overpayment, it shall be credited by Landlord to Tenant against the
      Rent next due hereunder, provided that any excess credit shall be repaid
      to Tenant within thirty (30) days following the end of the fiscal year in
      which occurs the expiration of the Lease Term, subject to set off against
      sums due from Tenant to Landlord.

      Part Years: If this Lease shall commence or terminate in the middle of a
      computation year Tenant shall be liable for only that portion of the Tax
      Excess in respect of such computation year represented by a fraction the
      numerator of which is the number of days of the herein Lease Term which
      falls within the computation year and the denominator of which is
      three-hundred sixty-five (365).

      Refunds: If, after Tenant shall have made any payment of Tax Excess to
      Landlord pursuant to this Section, Landlord shall receive a refund of
      taxes paid during or with respect to any real estate tax fiscal year
      during the Lease Term hereof as a result of abatement of such Taxes by
      legal proceedings, settlement or otherwise (without either party having an
      obligation to undertake any such proceedings), Landlord shall pay or
      credit to Tenant, Tenant's Proportionate Share of the refund (less the
      proportional, pro rata expenses, including administrative costs, attorneys
      fees and appraisers fees, incurred in connection with obtaining any such
      refund), as relates to Taxes paid by Tenant to Landlord with respect to
      any such fiscal year for which a refund is obtained. Tenant shall have no
      right to seek or to control any abatement, dispute, or other proceedings
      with the Town of Rockland or any other governmental agency or entity in
      connection with the Property.

      Data: Landlord shall promptly provide to Tenant, upon request made within
      thirty (30) days of receipt of any Tax Escalation Statement, reasonable
      data to permit Tenant to verify the Taxes contained therein, but Tenant
      may not dispute any such element of cost or expenses not objected to
      within sixty (60) days of receipt of such Tax Escalation Statement. Any
      obligation under this Section of the Tenant which shall not have been paid
      at the expiration of the Lease Term shall survive such expiration and
      shall be paid when and as the amount of same shall be determined together
      with interest thereon at the Lease Interest Rate from the date the Tax
      Excess was first due to Landlord.

      The additional rent required to be paid by Tenant pursuant to this
      Section, together with the Base Rent and the additional rent required to
      be paid by Tenant pursuant to this Lease, is hereinafter collectively
      called the "Rent."

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7. Building and Equipment: Unless any such damage or violation is caused by
Landlord or its employees or agents, Tenant shall maintain the Leased Premises
and will make all changes and repairs required to keep the Leased Premises in
good repair and condition and in compliance with all applicable laws, orders,
rules or regulations of any governmental agency having jurisdiction including,
without limitation, repairs to doors, locks, hardware, carpets, walls, ceilings,
electrical and lighting fixtures, fixtures and glass in the Leased Premises.
Tenant shall maintain Kitchen Areas and all similar areas in a clean and
sanitary condition free of all vermin, wash any dishes and perform any cleaning
necessary to maintain Kitchen Areas or any other areas in the Leased Premises in
which beverages or foods may be prepared, dispensed or consumed. Tenant shall be
responsible for any damage to the Leased Premises arising out of frozen
sprinkler system pipes caused by Tenant's failure to keep windows in the Leased
Premises closed during cold weather. Landlord shall keep in serviceable
condition and repair the structure and exterior of the Building and the
plumbing, electrical and service lines furnished by Landlord, unless any such
need for repair shall be caused by the negligence or misconduct of Tenant or any
party acting under Tenant. Landlord shall comply with applicable governmental
rules, regulations, laws and ordinances affecting the Building, unless the
violation is caused by Tenant or Tenant's use of the Leased Premises or Tenant's
neglect in connection therewith. The Landlord shall keep the grounds, parking
areas, walkways, common corridors, stairways, elevators and all other public
portions of the Building and Property in serviceable repair and in a reasonably
clean and safe condition, such repair and condition to be to the equivalent
standard prevalent in other office buildings on the South Shore of similar age,
location and condition. Tenant, at its own expense, shall supply all light bulbs
and ballasts having energy efficient characteristics and otherwise reasonably
acceptable to Landlord, tubes or similar devices for lighting the Leased
Premises and Landlord may (but shall be under no obligation to do so) offer to
supply such devices for a fee to be established by Landlord, in its sole
discretion, and to be paid by Tenant to Landlord in addition to any other
payments pursuant to the terms of this Lease. Landlord reserves the right to
interrupt, curtail, stop and suspend the furnishing of any services and the
operation of the plumbing, electrical, heating, ventilation and air-conditioning
systems when necessary by reason of accident or emergency or for repairs,
alterations, replacements or improvements which may become necessary in the
reasonable judgment of Landlord or when Landlord cannot secure supplies or
labor, or by reason of any other cause beyond its control, without liability or
any abatement of rent being due thereby.

Notwithstanding the foregoing or any other provision of the Lease, however,
Tenant shall not be responsible for compliance with any such laws, regulations,
or the like requiring (i) structural repairs or modifications or (ii) repairs or
modifications to the utility or building service equipment or (iii) installation
of new building service equipment, such as fire detection or suppressions
equipment, unless such repairs, modifications, or installations shall be due to
Tenant's particular manner of use of the Leased Premises (as opposed to office
use and research and development generally).

Notwithstanding the above, Landlord shall make reasonable, good faith efforts to
avoid the interruption of any services which it is obligated to provide. Tenant
shall be entitled to an abatement of Rent for interruption of services only to
the extent covered by Landlord's interruption insurance. Tenant shall cooperate
with Landlord by giving Landlord prompt written notice of the need for any
repairs to equipment which Landlord is responsible for or of any interruption in
Building services

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for which Landlord is responsible.

In the event of any emergency situation involving an actual risk to human life
or public safety which would otherwise be the responsibility of Tenant, Landlord
shall have the right, but shall not be required, to pay such sums or to do any
act which is necessary to abate said emergency on a temporary basis. If, and in
the event of, the exercise of such right Landlord incurs costs which are the
responsibility of the Tenant under this Lease, Tenant shall promptly reimburse
Landlord upon receipt of actual proof of the costs incurred.

8. Property of Tenant: Tenant shall not place a load upon any floor of the
Leased Premises which exceeds the floor load per square foot of area which such
floor was designed to carry or which is allowed by law. Business machines and
mechanical equipment and Tenant's other personal property shall be placed and
maintained by Tenant at its expense in settings sufficient to absorb and prevent
vibration, noise and annoyance. Tenant covenants and agrees that all of Tenant's
property of every kind, nature and description which may be in or upon the
Leased Premises or Building, in the public corridors, or on the sidewalks,
areaways and approaches adjacent thereto, during the Lease Term hereof, and any
movement of such property shall be at the sole risk and hazard of Tenant, and
Tenant hereby indemnifies and agrees to save Landlord harmless from and against
any liability, loss, injury, claim or suit resulting directly or indirectly
therefrom.

9. Services:

      (a) Except if such is interrupted for reasons beyond Landlord's control or
      must be stopped for necessary repairs in the reasonable judgment of the
      Landlord, the Landlord shall provide:

            1. Access to the Building to duly authorized employees of Tenant 24
            hours per day, seven days per week by means of an access control
            system.

            2. Necessary elevator facilities.

            3. Heat and air conditioning to the Leased Premises without
            additional charge during regular business hours (from 8:00 a.m. to
            6:00 p.m. Monday through Friday and 9:00 a.m. to 1:00 p.m. on
            Saturday, except customary holidays, as designated by the Landlord).
            By reasonable advance arrangement with the Building's manager, heat
            or cooling can be furnished at other times at an hourly rate to be
            established by Landlord, in its reasonable discretion, and to be
            paid by the Tenant to Landlord in addition to any other payments
            pursuant to this Lease.

            4. Cleaning of the Leased Premises and the lobby, elevators, public
            corridors, washrooms, and stairs which Tenant has the right to use
            in common with others, all in accordance with the Cleaning
            Specifications attached to this Lease as Exhibit C and made a part
            hereof.

            5. Normal lighting of the main lobby, elevators, washrooms and
            stairs, but not for the Leased Premises.

                                       8
<PAGE>

            6. Shoveling of snow and sanding of ice in the parking areas and on
            walkways on the Property in a manner provided by comparable office
            buildings in the vicinity.

      (b) Electricity, for all uses within the Leased Premises except general
      heating and air conditioning referred to in subparagraph 3 above, is to be
      paid for by Tenant. Since electricity is not presently metered to the
      Leased Premises, it is agreed that a fixed amount as specified as Cost of
      Electricity in the Reference Data Section shall be paid by Tenant for
      electricity in addition to the Rent. Landlord may at its cost install a
      utility meter. Tenant shall thereafter pay the billing authority all bills
      for electricity, and this obligation to pay the Cost of Electricity shall
      cease. Upon request of the Landlord, the Tenant shall promptly furnish to
      the Landlord evidence of such payment.

10. Removal of Goods and Tenant's Repairs. At the expiration of the Lease Term,
the Tenant shall remove its goods and effects (except as elsewhere provided
herein) and will peaceably yield up to Landlord the Leased Premises in as good
order and condition as when delivered to it, excepting ordinary wear and tear,
repairs required to be made by Landlord and damage by fire or casualty or taking
by eminent domain.

Tenant shall be responsible for all damage or injury to the Leased Premises,
fixtures, appurtenances and equipment of Landlord, or to the Building, caused by
Tenant's installation or removal of furniture, fixtures or equipment.

11. Improvements, Alterations and Ownership.

      (a) Landlord's Initial Construction. Landlord agrees to perform work and
      make installations in the Leased Premises as set forth in Schedule A. Such
      work and installations are referred to as "Landlord's Initial
      Construction." All of the terms, covenants and conditions of Schedule A.
      are incorporated in this Lease by reference and shall be deemed a part of
      this Lease as though fully set forth in the body of this Lease.

      (b) Alterations. Other than Landlord's Initial Construction, Tenant shall
      not make or perform, or permit the making or performance of, any
      alterations, installations, decorations, improvements, additional or other
      physical changes in or about the Leased Premises (referred to collectively
      as "Alterations" without Landlord's prior consent, which consent shall not
      be unreasonably withheld, conditioned or delayed. Notwithstanding the
      foregoing provisions of this Section or Landlord's consent to any
      Alterations, all Alterations shall be made and performed in conformity
      with and subject to the following provisions: All Alterations shall be
      made and performed at Tenant's sole cost and expense and at such time and
      in such manner as Landlord may, from time to time, reasonably designate;
      all Alterations shall, when completed, be of such a character as not to
      materially reduce the economic value of the Building below its value
      immediately before such Alterations; no Alterations shall diminish or
      reduce the structural integrity of the Building; alterations shall be made
      only by contractors or mechanics approved by Landlord, such approval not
      unreasonably to be withheld; no Alteration shall affect any part of the
      Building other than the Leased Premises or adversely

                                       9
<PAGE>

      affect any service required to be furnished by Landlord to Tenant or to
      any other tenant or occupant of the Building or reduce the value or
      utility of the Building; no Alteration shall affect the outside appearance
      of the Building; no Alteration shall affect the color or style of any
      Venetian blinds (except that Tenant may remove any Venetian blinds
      provided that they are promptly replaced by Tenant with building standard
      blinds or blinds substantially identical to building standards); all
      business machines and mechanical equipment shall be placed and maintained
      by Tenant in settings sufficient, in Landlord's reasonable judgment, to
      absorb and prevent vibration, noise and annoyance to other tenants or
      occupants of the Building; Tenant shall submit to Landlord detailed plans
      and specifications (including layout, architectural, mechanical and
      structural drawings) for each proposed Alteration and shall not commence
      any such Alteration without first obtaining Landlord's approval of such
      plans and specifications; prior to the commencement of each Alteration,
      Tenant shall have procured and paid for, and exhibited to Landlord, so far
      as the same may be required from time to time, all permits and
      authorizations of all municipal departments and governmental subdivisions
      and authorities having or claiming jurisdiction; prior to the commencement
      of each proposed Alteration, Tenant shall furnish to Landlord duplicate
      original policies of workmen's compensation insurance or certificates
      thereof reasonably satisfactory to Landlord covering all persons to be
      employed in connection with such Alteration, including those to be
      employed by all contractors and subcontractors, and of comprehensive
      public liability insurance (including property damage coverage) in which
      Landlord and its agents shall be named as parties insured, which policies
      shall be issued by companies, and shall be in form and amounts, reasonably
      satisfactory to Landlord and shall be maintained by Tenant until the
      completion of such Alteration; no Alterations in or to the electrical
      facilities in or serving the Leased Premises shall exceed the capacity of
      the existing feeders or wiring installations then serving the Leased
      Premises; electrical and air conditioning certificates, and all other
      permits, approvals and certificates required by all governmental
      authorities shall be timely obtained by Tenant and submitted to Landlord;
      all Alterations, once commenced, shall be made promptly and in a good and
      workmanlike manner; notwithstanding Landlord's approval of plans and
      specifications for any Alteration, all Alterations shall be made and
      performed in full compliance with all applicable laws, orders and
      regulations (including, but not limited to, the energy conservation
      provisions of the Massachusetts Building Code) of Federal, State, County
      and Municipal authorities and with all directions of all public officers,
      and with all applicable rules, orders, regulations and requirements of the
      New England Fire Insurance Rating Organization or any similar body; all
      Alterations shall be made and performed in accordance with the Rules and
      Regulations; all materials and equipment to be installed, incorporated or
      located in the Leased Premises as a result of any Alteration shall be new
      and first quality; no such materials or equipment shall be subject to any
      lien, encumbrance, chattel mortgage or title retention or security
      agreement or any kind; Tenant, before commencement of such Alteration,
      shall furnish to Landlord and its mortgagees a statutory lien bond and a
      performance bond or other security reasonably satisfactory to Landlord and
      such mortgagees in an amount at least equal to the estimated cost of such
      Alteration; in the event Landlord or its agents employ any independent
      architect or engineer to examine any plans or specifications submitted by
      Tenant to Landlord in connection with any proposed Alteration, Tenant
      agrees to pay to Landlord a sum equal to any reasonable fees incurred by
      Landlord in connection therewith.

                                       10
<PAGE>

      (c) No Consent or Request of Landlord. Nothing in this Lease shall be
      deemed or construed in any way as constituting the consent or request of
      Landlord, express or implied, by inference or otherwise, to any
      contractor, subcontractor, laborer or materialman, for the performance of
      any labor or the furnishing of any material for any specific Alteration
      to, or repair of, the Leased Premises, the Building, or any part of
      either. Any mechanic's or other lien filed against the Leased Premises or
      the Building or the Property for work claimed to have been done for, or
      materials claimed to have been furnished to, Tenant, or based upon any act
      or omission or alleged act or omissions of Tenant, shall be discharged by
      Tenant, at Tenant's sole cost and expense, within ten (10) days after the
      filing of such lien.

      (d) Labor Conflict. Tenant shall not knowingly, at any time prior to or
      during the Lease Term, directly or indirectly employ, or permit the
      employment of, any contractor, mechanic or laborer in the Leased Premises,
      whether in connection with any Alteration or otherwise, if such employment
      will interfere or cause any conflict with other contractors, mechanics or
      laborers engaged in the construction, maintenance or operation of the
      Building by Landlord, Tenant or others. In the event of any such
      interference or conflict, Tenant, upon request of demand of Landlord shall
      cause all contractors, mechanics or laborers causing such interference or
      conflict to leave the Building immediately.

      (e) Ownership of Improvements. All appurtenances, fixtures, improvements,
      additions and other property attached to or installed in the Leased
      Premises, whether by Landlord or Tenant or others, and whether at
      Landlord's expense, or Tenant's expense, or the joint expense of Landlord
      or Tenant or others, shall be and remain the property of Landlord, except
      that any such fixtures, improvements, additions and other property which
      is (i) installed at the sole expense of Tenant with respect to which
      Tenant has not been granted any credit or allowance by Landlord, whether
      pursuant to Schedule A or otherwise, (ii) which are removable without
      material damage to the said premises, and (iii) as to which Tenant shall
      have given notice to Landlord requesting the identification of such
      property without reasonable objection by Landlord, shall be and remain the
      property of Tenant and are referred to as "Tenant's Personal Property".
      Any replacements of any property of Landlord, whether made at Tenant's
      expense or otherwise, shall be and remain the property of Landlord.

12. Inspection. The Landlord and its authorized representatives shall have the
right at all reasonable times to enter the Leased Premises for reasonable
business purposes including, without limitation, inspecting the same and to be
accompanied by representatives of mortgagees, insurers or similar persons, to
make repairs or replacements therein as required by this Lease, to introduce
conduits and pipes or ducts as may be necessary in Landlord's reasonable
judgment; and to exhibit the Leased Premises to prospective tenants or others,
provided, however, that the Landlord shall use reasonable efforts not to unduly
disturb Tenant's use and occupancy. Landlord shall not be liable to Tenant in
any manner for any expense, loss or damage occurring by reason of the aforesaid
entries, nor shall the exercise of any such right be deemed an eviction or
disturbance of Tenant's use or possession, unless caused by the negligence or
misconduct of Landlord, its agents or invitees.

13. Casualty. If the Leased Premises, but not including other improvements made
by Tenant within the Leased Premises (but including Landlord's Initial
Construction), or any part thereof shall

                                       11
<PAGE>

be damaged by fire or other casualty, Landlord shall proceed with reasonable
diligence, and at the expense of Landlord, to repair or cause to be repaired
such damage; provided, however, that Landlord's obligations with respect to
restoration shall not require Landlord to expend more than the net proceeds of
insurance recovered and available to Landlord. Landlord shall have no
responsibility for any repairs or damage to or replacements of, Tenant's
personal property and property which Tenant may be required to remove as
provided in this Lease. All such repairs and replacements shall be promptly made
by and at the expense of Tenant. If the Leased Premises, but not including the
Improvements within the Leased Premises, or any part thereof, shall have been
rendered unfit for use and occupation hereunder by reason of such damage for a
period of five (5) or more days, the Base Rent or a just and proportionate part
thereof, according to the nature and extent to which the Leased Premises shall
have been so rendered unfit, shall be suspended or abated retroactive to the
date on which such portion of the Leased Premises became unfit for occupancy,
until the Leased Premises (except as to the property which is to be repaired by
or at the expense of Tenant) shall have been restored as nearly as practicably
may be to the condition in which they were immediately prior to such fire or
other casualty. Within sixty (60) days of such damage, Landlord shall give
Tenant notice ("Landlord's Notice") in writing of its reasonable estimate of the
length of time it will take to restore such damage ("Estimated Time to Repair").
If the Estimated Time to Repair is one hundred eighty (180) days or less from
the date of casualty, Landlord shall proceed to make repairs. If Landlord fails
to substantially so restore (to a condition of Substantial Completion as defined
in Schedule A-1) the Leased Premises within one hundred eighty (180) days from
the date of such damage, (as such period may be extended on account of delays in
such completion which are beyond the reasonable control of Landlord), Tenant
may, if it has paid all sums then payable to Landlord, terminate this Lease by
notice to Landlord and this Lease shall terminate forty-five (45) days after
delivery of such notice fully as if such date were the original expiration date
of this Lease; provided, that if Landlord substantially restores the Leased
Premises within such forty-five (45) day period such termination shall be deemed
null and void and the Lease will continue as if such restoration occurred within
the one hundred eighty (180) day period. Landlord shall not be liable for delays
in the making of any such repairs which are due to governmental regulations,
casualties and strikes, unavailability of labor and materials, and other causes
beyond the control of Landlord, nor shall Landlord be liable for any
inconvenience or annoyance to Tenant or injury to the business of Tenant
resulting from such delays in repairing such damage. If the Estimated Time to
Repair, as specified in Landlord's notice, exceeds one hundred eighty (180)
days, Tenant may terminate the Lease by giving written notice ("Tenant's
Notice") to Landlord within five (5) business days of its receipt of Landlord's
Notice specifying the Estimated Time to Repair, the effective date of such
termination to be thirty (30) days from the date of Tenant's Notice.
Notwithstanding the foregoing, if either (a) the Leased Premises shall be
damaged materially by any such fire or other casualty during the last year of
the Lease Term, or (b) all or any substantial part of the Leased Premises or the
Building is so damaged by such fire or other casualty that repair or
reconstruction (may reasonably be expected to take longer than one hundred eight
(180) days from the date of such casualty to complete (in the reasonable
judgment of Landlord) whether or not the Leased Premises shall have been damaged
by such fire or other casualty, then in either such case this Lease and the term
hereof may be terminated at the election of the Landlord by notice in writing of
its election so to terminate given within sixty (60) days of the occurrence of
such casualty, to be effective not less than thirty (30) days after the day on
which such termination notice is received. In the event of any such termination,
this Lease and the Lease Term hereof shall expire as of such effective
termination date

                                       12
<PAGE>

and the Base Rent and additional rent shall be apportioned as of such date; and
if the Leased Premises or any part thereof shall have been rendered unfit for
use and occupation by reason of such damage the Base Rent for the period from
the date of the fire or other casualty to the effective termination date, or a
just and proportionate part thereof, according to the nature and extent to which
the Leased Premises shall have been so rendered unfit, shall be abated.

14. Condemnation - Eminent Domain.

      (a) In the event that the Leased Premises or any substantial part thereof,
      or the whole or any substantial part of the Building, or the access
      thereto, shall be taken or appropriated by eminent domain or shall be
      condemned for any public or quasi-public use, or (by virtue of any such
      taking, appropriation or condemnation) shall suffer any damage (direct,
      indirect or consequential) for which Landlord or Tenant shall be entitled
      to compensation, then (and in any such event) this Lease and the Lease
      Term hereof may be terminated at the election of Landlord by a notice in
      writing of its election so to terminate which shall be given by Landlord
      to Tenant within sixty (60) days following the date on which Landlord
      shall have received notice of such taking, appropriation or condemnation.
      If the entire Leased Premises or such portion thereof or the access
      thereto shall be so taken, appropriated or condemned, such that Tenant
      shall be precluded from effectively utilizing the Leased Premises in the
      reasonable judgment of Landlord, then (and in any such event) this Lease
      and the Lease Term hereof may be terminated at the election of Tenant by a
      notice in writing of its election so to terminate which shall be given by
      Tenant to Landlord within sixty (60) days following the date on which
      Tenant shall have received notice of such taking, appropriation or
      condemnation. Upon the giving of any such notice of termination (either by
      Landlord or Tenant) this Lease and the Lease Term hereof shall terminate
      on or retroactively as of the date on which Landlord or Tenant, as the
      case may be, shall be required to vacate any portion of the area so taken,
      appropriated or condemned or shall be deprived of the means of access
      thereto, provided, however, that Landlord may in Landlord's notice of
      termination elect to terminate this Lease and the Lease Term hereof
      retroactively as of the date on which such taking, appropriation or
      condemnation became legally effective. In the event of such termination
      this Lease and the Lease Term hereof shall expire as of such effective
      termination date and the Rent shall be apportioned as of such date.

      (b) If neither party (having the right so to do) elect to terminate this
      Lease and the Lease Term hereof, Landlord shall, with reasonable diligence
      and at Landlord's expense, restore the remainder of the Leased Premises
      (but not any of Tenant's Personal Property), or the remainder of the means
      of access, as nearly as practicably may be to the condition prior to such
      taking, appropriation or condemnation, in which event the Rent shall be
      adjusted in a manner such that (i) a just proportion of the Base Rent and
      additional rent, according to the nature and extent of the taking,
      appropriation or condemnation and the resulting permanent injury to the
      Leased Premises and the means of access thereto, shall be permanently
      abated and (ii) a just proportion of the remainder of the Base Rent and
      additional rent, according to the nature and extent of the taking,
      appropriation or condemnation and the resultant injury sustained to the
      Leased Premises and the means of access thereto, shall be abated until
      what remains of the Leased Premises (other than any property to Tenant)
      and the means of access thereto shall have been

                                       13
<PAGE>

      restored for permanent use and occupation by Tenant hereunder. Landlord
      shall not be liable for any delays in such restoration which are due to
      governmental regulations, casualties, strikes, unavailability of labor or
      materials, or other causes beyond Landlord's control nor shall Landlord be
      liable for any inconvenience or annoyance to Tenant or injury to the
      business of Tenant resulting from such delays in such restoration.
      Landlord expressly reserves and Tenant hereby assigns to Landlord all
      rights to compensation and damages created, accrued or accruing by reason
      of any such taking, appropriation or condemnation, but not including
      relocation assistance payments by a governmental agency or entity for
      which Tenant may be eligible.

      (c) If the Leased Premises or any part thereof or the access thereto shall
      be taken, appropriated or condemned for any temporary use (i) this Lease
      shall be and remain unaffected thereby and Tenant shall continue to pay
      the full amount of the Rent hereunder, (ii) Tenant shall be entitled to
      receive for itself any award made for such use allocable to the Lease
      Term, and (iii) Tenant shall be responsible for any repairs necessary to
      restore the Leased Premises to their condition prior to such taking,
      appropriation or condemnation, provided that if any such taking,
      appropriation or condemnation extends beyond the Lease Term, the costs of
      such repairs shall be allocated between Landlord and Tenant in proportion
      to the amount of any award each receives. Any taking, appropriation or
      condemnation continuing in excess of one year shall be deemed to be a
      permanent taking, appropriation or condemnation and shall be governed by
      paragraph (a) and (b) above.

15. Indemnification. Tenant hereby indemnifies and covenants to save Landlord
harmless from and against any and all claims, liabilities or penalties asserted
by or on behalf of any person, firm corporation, public authority or other
entity:

      (a) On account of or based upon any injury to person, or loss of or damage
      to property, sustained or occurring on the Leased Premises on account of
      or based upon the act, omission, fault, negligence or misconduct of any
      person other than Landlord or its servants, agents or employees;

      (b) On account of or based upon any injury to person, or loss of or damage
      to property, sustained or occurring in or about the Property and other
      than on the Leased Premises (and, in particular, without limiting the
      generality of the foregoing, on or about the elevators, stairways, public
      corridors, sidewalks, concourses, arcades, approaches, areaways, roof or
      other appurtenances and facilities used in connection with the Building or
      the Leased Premises) arising out of the use or occupancy of the Building
      or the Leased Premises by the Tenant or by any person claiming by, through
      or under Tenant, and caused by the act, omission, fault, negligence or
      misconduct of any person other than Landlord or its servants, agents or
      employees, and in addition to and not in limitation of the foregoing
      subdivision (a);

      (c) On account of or based upon (including monies due on account of) any
      work or thing whatsoever done (other than by Landlord or its contractors,
      or agents or employees of either) on the Leased Premises during the Lease
      Term and during the period of time, if any, prior to the Commencement Date
      when Tenant may have been given access to the Leased Premises;

                                       14
<PAGE>

      and

      (d) In respect of any of the foregoing, from and against all costs,
      expenses (including, without limitation, reasonable attorneys' fees) and
      liabilities incurred in or in connection with any such claim, or any
      action or proceeding brought thereon; and in case any action or proceeding
      be brought against Landlord by reason of any such claim, Tenant upon
      notice from Landlord shall at Tenant's expense resist or defend such
      action or proceeding and employ counsel therefor reasonably satisfactory
      to Landlord, it being agreed that such counsel as may act for insurance
      underwriters of Tenant engaged in such defense shall be deemed
      satisfactory.

16. Liability Insurance. Tenant agrees to maintain public liability insurance
and property damage liability insurance in the amounts set forth in the
Reference Data section and to submit and maintain copies of such policies with
the Landlord. The insurers under such policies shall be reasonably satisfactory
to Landlord and such policies shall name as insured parties Landlord, Tenant and
any Mortgagee of which Tenant has received notice or otherwise has actual
knowledge, as their interest may appear, and shall provide twenty (20) days
prior written notice to Landlord or any such Mortgagee of lapse or cancellation.

17. Damage to Property of Tenant. In addition to and not in limitation of the
foregoing, Tenant covenants and agrees that all Tenant's furniture, fixtures and
property of every kind, nature and description which may be in or upon the
Leased Premises or Building, in the public corridors, or on the sidewalks,
areaways and approaches adjacent thereto, during the term hereof, shall be at
the sole risk and hazard of Tenant, and that if the whole or any part thereof
shall be damaged, destroyed, stolen or removed for any cause or reason
whatsoever no part of said damage or loss shall be charged to, or borne by
Landlord. Tenant agrees to maintain all risk insurance on the full insurable
value of all personalty located on the Leased Premises and to submit and
maintain copies of such policies with Landlord.

18. Injury and Damage. Landlord shall not be liable for any injury or damage to
persons or property resulting from fire, explosion, falling plaster, steam, gas,
electricity, electrical disturbance, water, rain or snow or leaks from any part
of the Building or from the pipes, appliances or plumbing works or from the
roof, street or subsurface or from any other place or by dampness or by any
other cause of whatever nature, unless caused by or due to the act, omission,
fault, negligence or misconduct of Landlord, or its agents, servants or
employees; nor shall Landlord or its agents be liable for any such damage caused
by other tenants or persons in the Building or caused by operations in
construction of any private, public or quasi-public work; nor shall Landlord be
liable for any latent defect in the Leased Premises or in the Building.

19. Waiver of Subrogation / Landlord's Insurance.

      (a) Tenant and Landlord covenant that with respect to any property
      insurance coverage carried by either Tenant or Landlord in connection with
      the Leased Premises or the Building whether or not such insurance is
      required by the terms of this Lease, such insurance shall provide for the
      waiver by the insurance carrier of any subrogation rights against
      Landlord, its agents, servants and employees under Tenant's insurance
      policies or against Tenant, its agents,

                                       15
<PAGE>

      servants, and employees under Landlord's insurance policies, where such
      waiver of subrogation rights does not require the payment of an additional
      premium or, if an additional premium is required to be paid, the other
      party offers to pay such premium after being notified of such additional
      premium.

      (b) Notwithstanding any other provision of this Lease, (i) Landlord shall
      not be liable to Tenant for any loss or damage, whether or not such loss
      or damage is caused by the negligence of Landlord, its agents, servants or
      employees, to the extent that such loss or damage is covered by valid and
      enforceable insurance carried by Tenant; and (ii) Tenant shall not be
      liable to Landlord for any loss or damage, whether or not such loss or
      damage is caused by the negligence of Tenant or its agents, servants or
      employees, to the extent that such loss or damage is covered by valid and
      enforceable insurance carried by Landlord.

      (c) Landlord shall procure and keep in force "all risk" property insurance
      on the Building with terms and coverage required by any institutional
      mortgagee of the Building or, if there exists no such mortgagee, as
      reasonably determined by Landlord to be consistent with similar policies
      customary for first class buildings in the Greater Boston marketplace.

20. Assignment, Mortgaging and Subletting.

      (a) Tenant covenants and agrees that neither this Lease nor the Lease Term
      and estate hereby granted, nor any interest herein or therein, will be
      assigned, mortgaged, pledged, encumbered or otherwise transferred, and
      that neither the Leased Premises, nor any part thereof, will be encumbered
      in any manner by reason of any act or omission of Tenant, or used or
      occupied, or permitted to be used or occupied, by anyone other than
      Tenant, its servants, agents and employees, or for any use or purpose
      other than as above stated, or be sublet, or offered, or advertised for
      subletting, without in each case, Landlord's prior written consent.
      Landlord may refuse to consider a request for such consent and may
      withhold such consent unless Tenant shall have agreed to reimburse
      Landlord promptly for reasonable expenses, including legal expenses,
      incurred by Landlord in connection with such request. If Tenant shall
      propose any subletting of more than half of the Leased Premises or any
      assignment of this Lease, Landlord shall have the option of terminating
      this Lease by giving notice thereof to Tenant.

      Any assignment of this Lease made hereunder shall be upon the express
      condition that the assignee and Tenant shall promptly execute, acknowledge
      and deliver to Landlord an agreement in form and substance satisfactory to
      Landlord whereby assignee shall agree to be personally bound by the terms,
      covenants, and conditions of this Lease on Tenant's part to be performed
      and whereby assignee shall expressly agree that the provisions of this
      Section shall, notwithstanding such assignment or transfer, continue to be
      binding upon it with respect to all future assignments and transfer. Any
      sublease of the Leased Premises or any part thereof shall be expressly
      subject to the terms of this Lease and shall contain the agreement of the
      subtenant thereunder that, upon Landlord's written request, it will pay
      all rents under the sublease directly to Landlord. If, pursuant to the
      provisions of this Section, Tenant sublets the Leased Premises or any part
      thereof, Tenant shall pay to Landlord as additional rent at the times and
      in the manner specified by Landlord, an amount equal to the difference
      between all amounts

                                       16
<PAGE>

      which Tenant receives from a subtenant by virtue of such subletting (less
      the amortization of reasonable costs incurred by Tenant in direct
      connection with such subletting) and the total of the Rent due under this
      Lease for the sublet area proportioned on a square foot basis; provided
      said difference is greater than zero. No such assignment or subletting of
      the Leased Premises by Tenant shall relieve Tenant from the observance or
      performance of any of the terms, covenants and conditions of this Lease.

      (b) If this Lease be assigned, or if the Leased Premises or any part
      thereof be sublet or occupied by anybody other than Tenant and its
      employees, Landlord, after default by Tenant hereunder, may collect the
      rents from such assignee, subtenant or occupant, as the case may be, and
      apply the net amount collected to the Rent herein reserved, but no such
      assignment, subletting, occupancy or collection shall be deemed a waiver
      of the requirements set forth in subparagraph (a) of this Section, the
      acceptance by Landlord of such assignee, subtenant or occupant, as the
      case may be, as a tenant, or a release by Tenant of its covenants,
      agreements and obligations contained in this Lease. The consent by
      Landlord to an assignment or subletting shall not in any way be construed
      to relieve Tenant from obtaining the express consent in writing of
      Landlord to any further assignment or subletting. No assignment,
      subletting or use of the Leased Premises shall affect the purpose for
      which the Leased Premises may be used as stated in Section 2.

      (c) Notwithstanding the foregoing, Tenant may assign this Lease or
      sublease any portion of the Leased Premises to any entity which is a
      parent or subsidiary corporation of Tenant or to any entity with which
      Tenant may merge or consolidate or to which Tenant may sell all of
      substantially all of its assets as a going concern in exchange for
      assumption of all or substantially all of its liabilities (any of the
      foregoing entities being hereinafter referred to as a "Successor") but
      only if such Successor is of comparable character, quality and financial
      capacity as Tenant as of the date thereof, in Landlord's judgment;
      provided that simultaneously with any such assignment, Tenant shall
      deliver to Landlord an agreement in form and substance reasonably
      satisfactory to Landlord which contains an appropriate covenant of
      assumption by such assignee, and provided further that in the case of any
      such assignment or sublease to a Successor, Tenant shall have submitted to
      Landlord prior thereof financial information reasonably satisfactory to
      Landlord evidencing that such Successor has at least an equivalent net
      worth and other financial resources as Tenant and a general business
      reputation comparable to or superior to that of Tenant.

      (d) The listing of any name other than that of Tenant, whether on the
      doors or the Leased Premises or on the Building directory, or otherwise,
      shall not operate to vest any right or interest in this Lease or in the
      Leased Premises or be deemed to be the written consent of Landlord
      mentioned in this Section, it being expressly understood that any such
      listing is a privilege extended by Landlord revocable at will by written
      notice to Tenant.

      (e) Tenant further covenants and agrees that it will not sublease space
      from or take an assignment of a lease covering space in the Building from
      any other Building tenant, without Landlord's prior written consent.

                                       17
<PAGE>

      (f) Subject to the foregoing provisions of this Section, including,
      without limitation, Landlord's right to terminate this Lease in accordance
      with paragraph (a) above, Landlord agrees to not unreasonably withhold its
      consent to a subletting of all or a portion of the Leased Premises,
      provided that the Landlord shall determine, in its reasonable discretion,
      that (i) the prospective subtenant or assignee has personal references and
      the financial capacity to meet all of the obligations of this Lease and to
      carry out its business in a manner consistent with the level of Landlord's
      operation of the Building, (ii) the use of the Leased Premises under such
      sublease or assignment shall be for a first-class office use which is
      consistent with the mix of tenants in and the character of the Building,
      (iii) such use shall not materially burden the common areas or operating
      systems of the Building, and (iv) space reasonably comparable to that
      proposed to be sublet is not available from Landlord in the Building.

21. Signs and Drapes. No signs may be put on or in any window by Tenant. Tenant
may hang its own drapes, provided that such drapes are of a neutral color and
are completely screened from view from the exterior of the Building at all times
by building standard Venetian blinds. Any signs or lettering in the public
corridors or on the doors must be submitted to Landlord and its architect for
written approval of the size, color, design and location of such signs or
lettering before installation. Any sign of Tenant in the Leased Premises or in
the Building must comply with any applicable sign ordinances, and may not
conflict with the terms restricting signs in any other lease of space in the
Building. Notwithstanding the foregoing, Landlord shall provide the initial
building standard signage in the lobby directory.

22. Landlord's Insurance. Tenant will not do or omit to do or keep anything in,
upon or about the Leased Premises, the Building or any adjacent areas which may
prevent the obtaining of any fire, liability or other insurance upon or written
in connection with the Leased Premises, the Building or such adjacent areas or
which may make any such insurance void or voidable or otherwise invalidate the
obligations of the insurer contained therein, or which may create any extra
premiums or increase the rate of any such insurance over that normally
applicable to office buildings. Tenant agrees to pay to Landlord, upon demand,
the amount of any extra premiums or any increase in the rate of such insurance
which results from the business carried on in the Leased Premises by Tenant,
whether or not Landlord has consented to such business. If Tenant installs any
electrical equipment that overloads the lines in the Leased Premises, Tenant
shall, at its expense, make whatever changes are necessary to comply with the
requirements of the insurance underwriter or governmental authorities having
jurisdiction, but such changes shall be made in accordance with the provisions
of Section 11.

23. Inflammables, Odors. Tenant shall not bring or permit to be brought into or
keep in or on the Leased Premises or elsewhere in the Building, any inflammable,
combustible or explosive fluid, material, chemical or substance, or cause or
permit any odors or cooking or other processes, or any unusual or other
objectionable odors to emanate from or permeate the Leased Premises, except as
used in the ordinary course of businesses customarily located in first class
office buildings.

24. Default. If the Tenant shall default in the payment of the Rent or any other
charges due hereunder; or if the Tenant shall default in the performance of any
other of its obligations and such default shall continue for ten (10) days after
written notice thereof by the Landlord to the Tenant (except that if the Tenant
cannot reasonably cure any such default within said ten (10) day period,

                                       18
<PAGE>

this period may be extended for a reasonable time not to exceed thirty (30)
days, provided that the Tenant commences to cure such default within the ten
(10) day period and proceeds diligently thereafter to effect such cure); or if
the Tenant shall file a petition under any bankruptcy, insolvency law or code,
or if such a petition is filed against Tenant and not dismissed within sixty
(60) days; or if the Tenant shall be adjudicated bankrupt or insolvent according
to law; or if the Tenant shall make any assignment for the benefit of creditors;
or if the Tenant shall file any petition seeking a reorganization, arrangement
or similar relief; or if a receiver, custodian, trustee or similar agent of the
Leased Premises or of all or a substantial part of Tenant's assets shall be
authorized or appointed and not removed within sixty (60) days in the case of an
involuntary appointment; or if Tenant's interest in this Lease is taken upon
execution or other process of law in any action against Tenant; then the
Landlord may lawfully enter the Leased Premises and repossess the same as the
former estate of the Landlord, or terminate this Lease by written notice to
Tenant and, in either event, expel the Tenant and those claiming through or
under the Tenant, and remove their effects (forcibly, if necessary but in
conformity with applicable laws), without being deemed guilty of any manner of
trespass and without prejudice to any other remedy which the Landlord may have
for arrears of Rent and other charges due hereunder or proceeding on account of
breach of covenant, and upon entry or notice as aforesaid, this Lease shall
terminate. The Tenant covenants, in case of any default by Tenant hereunder, to
pay the Landlord all actual and reasonable costs of enforcing its rights under
this Lease (including, without limitation, reasonable attorney's fees and
expenses), loss of rent, reletting expenses, and brokerage fees together with,
as agreed liquidated damages, either of the following options as selected by
Landlord: (i) the amount by which, at the termination of the Lease, the
aggregate of the Rent (including, without limitation, the Operating Costs Excess
and the Tax Excess payments projected on the basis of experience under this
Lease) and other sums payable hereunder projected over a period from such
termination until the normal expiration date of the Lease Term exceeds the
aggregate projected fair market rental value of the Leased Premises for such
period discounted at the then current rate for U.S. Treasury obligations with a
maturity coinciding as closely as possible with the end of the Lease Term, or
(ii) an amount equal to the Rent (including, without limitation, Operating Costs
Excess and Tax Excess payments projected on the basis of experience under this
Lease) and other sums which would have been payable had the Lease not so
terminated (subject to off-set for net rents actually received from reletting
after subtraction of the expenses of reletting), payable upon the due dates as
specified herein.

Landlord may bring legal proceedings for the recovery of such damages, or any
installments thereof, from time to time at its election, and nothing contained
herein shall be deemed to require Landlord to postpone suit until the date when
the Lease Term would have expired if it had not been terminated hereunder.

Nothing herein contained shall be construed as limiting or precluding the
recovery by Landlord from Tenant of any sums or damages (including, without
limitation, reasonable attorneys' fees and expenses) to which, in addition to
the damages particularly provided above, Landlord may lawfully be entitled by
reason of any default hereunder on the part of Tenant.

Landlord and Tenant agree that, for the purpose of computing liquidated damages,
the Tax Excess payments and the Operating Costs Excess payments for the period
between the termination of this Lease pursuant to this Section and the normal
expiration date shall be computed by multiplying both

                                       19
<PAGE>

the Tax Excess payment and the Operating Costs Excess payment for the year
immediately preceding the year in which termination occurs times the number of
years remaining in the full Lease Term hereby granted on the assumption that the
amount of such Tax Excess payment and Operating Costs Excess payment for the
immediately preceding year would have remained constant for each subsequent year
during the full Lease Term. If this Lease and the Lease Term hereof shall
terminate pursuant to this Section prior to the determination of the initial Tax
Excess payment or Operating Costs Excess payment, the Tax Excess payment and the
Operating Costs Excess payment shall be reasonably estimated by Landlord.

Payment of Base Rent, Additional Rent, any other payment due as Rent, Operating
Costs Excess, Tax Excess and any other obligations of Tenant which are not paid
on the date due plus the applicable grace period, if any, shall, at the option
of Landlord, bear interest at the rate equal to prime rate published in the Wall
Street Journal, plus five (5%) percent per annum, or such lesser rate as may be
the highest rate allowed by law (the "Lease Interest Rate") from the due date
and shall be compounded monthly). If Tenant shall fail to make any payment,
including, without limitation, electricity, telephone or other charges which
Tenant makes directly to a utility or other company when due, and such failure
shall threaten the continued provision of such service to the Leased Premises,
Landlord or other tenants in the Building, Landlord may make such payment on
Tenant's behalf, and such amount shall be due from Tenant as Rent with interest
at the Lease Interest Rate.

25. Subordination.

      (a) This Lease and all rights of Tenant hereunder are, and shall remain
      unconditionally subject and subordinate in all respects to all mortgages
      which are or may hereafter be placed on or affect such Lease and/or the
      Property of which the Leased Premises are a part, or any part of such real
      property, and/or Landlord's interest or estate therein, and to each
      advance made and/or hereafter to be made under any such mortgages, and to
      all renewals, modifications, consolidations, replacements and extensions
      thereof provided that the holder of record thereof enters into a written
      agreement with Tenant binding upon the successors and assigns of the
      parties thereto by the terms of which such holder will agree, (a) to
      recognize the rights of Tenant under this Lease, (b) in the event of
      acquisition of title by said holder through foreclosure proceedings or
      otherwise, to perform Landlord's obligations hereunder arising after the
      date of such holder's acquisition of title, and (c) to accept Tenant as
      tenant of the Leased Premises under the terms and conditions of this
      Lease, and Tenant agrees to recognize such holder or any other person
      acquiring title to the Leased Premises as Landlord. This Section shall be
      self-operative and no further instrument of subordination shall be
      required. In confirmation of such subordination, Tenant shall execute and
      deliver promptly any certificate acknowledging or confirming such
      subordination that Landlord and/or any mortgagee and/or their respective
      successors in interest may request.

      (b) No act or failure to act on the part of Landlord which would entitle
      Tenant under the terms of this Lease, or by law, to be relieved of
      Tenant's obligations hereunder or to terminate this Lease shall result in
      a release or termination of such obligations or a termination of this
      Lease unless (i) Tenant shall have first given written notice of
      Landlord's act or failure to act to the holder of any mortgages of whom
      Tenant has been given written notice specifying the

                                       20
<PAGE>

      act or failure to act on the part of Landlord which could or would give
      basis to Tenant's rights; and (ii) the holder or holders of such
      mortgages, after receipt of such notice, have failed or refused to correct
      or cure the condition complained of within a reasonable time thereafter,
      but nothing contained in this sentence shall be deemed to impose any
      obligation on any such holders to correct or cure any such condition.
      "Reasonable time" as used above means and includes a reasonable time to
      obtain possession of the Building if any such holder elects to do so and a
      reasonable time (not to exceed ninety (90) days) to correct or secure the
      condition if such condition is determined to exist.

      (c) From time to time, within ten (10) days next following Landlord's
      request, Tenant shall deliver to Landlord a written statement executed and
      acknowledged by Tenant, in form reasonably satisfactory to Landlord, (i)
      stating that this Lease is then in full force and effect and has not been
      modified (or, if modified, setting forth the specific nature of all
      modifications), and (ii) setting forth the date to which the Base Rent has
      been paid, and (iii) stating whether or not, to the best knowledge of
      Tenant, Landlord is in default under this Lease, and, if Landlord is in
      default, setting forth the specific nature of all such defaults. Tenant
      acknowledges that any statement delivered pursuant to this paragraph may
      be relied upon by any purchaser or owner of the Building, or the Property
      or any part thereof, or Landlord's interest in the Building or the
      Property or by an mortgagee, or by any assignee of any mortgagee.

      (d) Tenant hereby agrees that this Lease shall be subject and subordinate
      to all the terms, conditions and provisions of any Master Deed,
      Declaration of Trust or By-Laws of any condominium regime created for the
      Building and which includes the Leased Premises and Tenant shall execute
      any reasonable instrument confirming said subordination and recognizing
      and consenting to said condominium regime, provided that Tenant's rights
      and obligations hereunder shall not be adversely affected thereby.

26. Holdover. If the Tenant remains in the Leased Premises beyond the expiration
or earlier termination of the Lease Term such holding over shall not be deemed
to create any tenancy, but the Tenant shall be a Tenant-at-Sufferance only and
shall pay rent to Landlord at the times and manner determined by Landlord at a
daily rate in an amount equal to two times the daily rate of the Rent and other
sums payable under this Lease as of the last day of the Lease Term.

27. Notices. Any notice or demand by Tenant to Landlord shall be served by hand
delivery, recognized overnight courier service, or registered or certified mail
addressed to the Landlord at the address above indicated, and until otherwise
directed in writing by the Landlord, and any notice or demand by Landlord to
Tenant shall be served by any of the same means addressed to Tenant at the
Leased Premises with a courtesy copy to Hale and Dorr LLP, 60 State Street,
Boston, MA 02109, Attn: Paul Jakobowski, Esq. (provided that the failure to
provide such copy shall not affect the effectiveness, enforceability or the
service of such notice) until otherwise directed in writing by Tenant. Any such
notice shall be deemed to have been given when it is received or on the date
that delivery is referred during normal business hours.

                                       21
<PAGE>

28. Rules and Regulations. Tenant will faithfully observe and comply with the
Rules and Regulations annexed hereto as Exhibit B and such other and further
reasonable Rules and Regulations as Landlord hereafter at any time or from time
to time may make and may communicate in writing to Tenant, which in the judgment
of Landlord shall be necessary for the reputation, safety, care or appearance of
the Building, or the preservation of good order therein, or the operation or
maintenance of the Building, or any equipment relating thereto, or the comfort
of Tenant or others in the Building. If this Lease shall conflict with any such
Rules and Regulations, the provisions of this Lease shall control. Landlord
shall not have any duty or obligation to enforce the Rules and Regulations or
the terms, covenants or conditions in any other lease as against any other
tenant and Landlord shall not be liable to Tenant for violation of the same by
other tenants, their servants, employees, agents, visitors, invitees or
licensees.

29. Quiet Enjoyment. The Tenant shall upon paying the Rent reserved herewith and
performing all of the terms, covenants and condition on Tenant's part to be
observed and performed, peaceably and quietly have and hold the Leased Premises
without hindrance or molestation by any person or persons lawfully claiming by,
through or under Landlord, subject, however, to the terms of this lease.

30. Disputes; Landlord's Reasonableness; Arbitration. Notwithstanding any other
provisions hereof to the contrary, Tenant's sole remedy in any dispute with
respect to the reasonableness of any failure or refusal of Landlord to grant its
consent or approval to any request for such consent or approval pursuant to any
of the provisions of this Lease with respect to which Landlord has covenanted
not unreasonably to withhold such consent or approval, shall be an action for
specific performance. If the determination of any such proceedings shall be
adverse to Landlord, Landlord shall be deemed to have granted the requested
consent or approval, but that shall be Tenant's sole remedy in such event and
Landlord shall not be liable to Tenant for any damages or for a breach of
Landlord's covenant not unreasonably to withhold such consent or approval, or
otherwise. Any dispute which Landlord and Tenant shall agree to submit to
arbitration shall be finally determined by arbitration in accordance with the
rules and regulations then obtaining of the American Arbitration Association or
its successor. Any such determination shall be final and binding upon the
parties, whether or not a judgment shall be entered in any court. In making a
determination, the arbitrators shall not subtract from, add to, or otherwise
modify any of the provisions of this Lease.

Landlord and Tenant may, at their own expense, be represented by counsel and
employ expert witnesses in any such arbitration.

31. Seisin. In the event of a sale or other disposition of the Building and/or
Property by Landlord, Landlord shall be entirely freed and relieved from the
performance and observance thereafter of all covenants and obligations of
Landlord hereunder, provided that the Landlord's successor shall thereupon
assume and agree thereafter to perform and observe, any and all of such
covenants and obligations of Landlord.

32. Binding Agreement. This Lease shall bind and inure to the benefit of the
parties hereto and their respective heirs, representatives, successors or
assigns. This Lease contains the entire agreement of the parties and many not be
modified except by an instrument in writing.

                                       22
<PAGE>

33. Notice of Lease. Tenant agrees that it will not record this Lease. Landlord
and Tenant shall, upon request of either, execute and deliver a notice of this
Lease in such recordable form as may be permitted by applicable statute.

34. Landlord's Right to Cure. If Tenant shall default in the observance or
performance of any term, covenant or condition on its part to be observed or
performed under this Lease, Landlord, without being under any obligation to do
so and without waiving such default, may remedy such default for the account and
at the expense of Tenant, immediately and without notice in case of emergency,
or in any other case, if Tenant, shall fail to remedy such default with all
reasonable diligence within the time set forth under Section 24 and after
Landlord shall be notified Tenant of such default. If Landlord makes any
expenditures or incurs any obligations of the payment of money in connection
therewith, including, but not limited to, reasonable attorneys fees, such sums
paid or obligations incurred, with interest at the Lease Interest Rate, shall be
paid to Landlord by Tenant as Rent hereunder.

35. Hazardous Materials. Tenant agrees to properly handle, store, use and
dispose of all hazardous material, as may be defined by applicable law. Without
limiting the foregoing, Tenant shall not dispose of such material on or into any
property of Landlord, any sewage or drainage system, or any trash receptacle
provided by Landlord. Prior to storing, handling, using, or disposing of any
hazardous material on the Leased Premises or the Property of Landlord, Tenant
shall notify Landlord of such activity and provide all reasonable evidence that
such material shall be dealt with in accordance with the terms of this Lease.
Tenant shall indemnify and hold Landlord harmless from all claims, including
costs and attorneys' fees arising from Tenant's possession of such materials.
This provision shall survive termination of this Lease.

36. First Offer for Basement Space.

      (a) Provided Tenant shall not be in default hereunder, then, if after the
      initial leasing of the basement of the Building, all or a portion of the
      basement becomes available for leasing and Tenant has notified Landlord
      that it has a need for additional space, then Landlord shall give notice
      of such availability to Tenant (the "Offer Notice") and Tenant shall have
      the option, exercisable only by notice given to Landlord within fifteen
      (15) days from the receipt of the Offer Notice and subject to the
      provisions hereof, to lease and add to the Leased Premises the space which
      is the subject of the proposal referred to in the Offer Notice, for a term
      to commence on the date designated in such Notice and ending on the
      Expiration Date (unless sooner terminated pursuant to this Lease or law),
      in an "as-is" condition, at rent and other conditions as described in the
      Offer Notice, and upon all the other then executory terms, covenants and
      conditions contained in this Lease. The terms contained in the Offer
      Notice shall be determined in good faith by the Landlord to reflect the
      fair market value for the premises described therein. Tenant may only
      exercise such option on all of the space so offered (the "Applicable Added
      Space").

      (b) No space shall be deemed to be "available for leasing" or otherwise
      subject to the provisions of this Section if the tenant of such space or
      any assignee or subtenant thereof enters into any agreement with Landlord
      relating to such space. It is understood and agreed that time

                                       23
<PAGE>

      is of the essence with respect to the exercise of any option set forth in
      this Section.

      (c) The lease term applicable to any space as to which Tenant can exercise
      the option under this Section shall be for at least three (3) years.
      Accordingly, the option set forth in this Section shall not be exercisable
      if the proposed term applicable to any such space commences on a date
      which is less than three (3) years prior to the Expiration Date then in
      effect.

      (d) With Tenant's notice, Tenant's shall provide Landlord with a complete
      description of its proposed operation in the Applicable Added Space, and
      if Landlord determines that such operation is not compatible and
      consistent with: (i) the Use of the Leased Premises; (ii) Landlord's
      operation of the Building; and (iii) other uses in the Building and the
      tenant mix therein, it may revoke Tenants option and render it null and
      void.

      (e) On the effective commencement date of the term applicable to the
      Applicable Added Space, this Lease shall be deemed modified as follows:

            (i) The Leased Premises shall include the Applicable Added Space
            (together with all appurtenances, fixtures, improvements, additions
            and other property attached thereto or installed therein at the
            commencement of the term applicable to the Applicable Added Space or
            at any time during said term, other than Tenant's Personal Property)
            for all purposes of this Lease;

            (ii) The Base Rent shall be increased by the base rent set forth in
            the proposal referred to in the Applicable Offer Notice with respect
            to the Applicable Added Space.

            (iii) Additional Rent shall include all other rent and charges
            proposed in the Offer Notice.

      (f) Upon request of Landlord, Tenant shall execute and deliver to Landlord
      an instrument, in reasonably satisfactory form and suitable for recording,
      stating that Tenant has not exercised an option which became available to
      it pursuant to this Section to lease any Applicable Added Space, if that
      be the case, or stating that Tenant has exercised such option, if that be
      the case, and setting forth all of the modifications to the Lease
      resulting from the application of the provisions of this Section,
      including, but not limited to, the effective commencement date of the term
      applicable to the Applicable Added Space. Neither Landlord's failure to
      request that Tenant execute such instrument nor Tenant's failure to comply
      with the provisions of this paragraph shall, however, vitiate the
      provisions of this Section.

37. General Provisions.

      (a) Except as provided in Section 30, the various rights and remedies
      contained in this Lease and reserved to each of the parties shall not be
      exclusive of any other right or remedy of such party, but shall be
      construed as cumulative and shall be in addition to every other remedy now
      or hereafter existing at law, in equity, or by statute. No delay or
      omission of the right to exercise any power by either party shall impair
      any such right or power or shall be construed

                                       24
<PAGE>

      as a waiver of any default or as acquiescence in any default. One or more
      waivers of any covenant, term or condition of this Lease by either party
      shall not be construed by the other party as a waiver of a subsequent
      breach of the same covenants, term or condition. The consent or approval
      of either party to or of any act by the other party of a nature requiring
      consent or approval shall not be deemed to waive or render unnecessary
      consent to or approval of any subsequent similar act.

      (b) Payments to Landlord under this Lease are rental for the use of the
      Leased Premises, and nothing herein contained shall be deemed or construed
      to make Landlord a partner or associate of Tenant in the conduct of any
      business, nor as rendering Landlord liable for any debts, liabilities or
      obligations incurred by Tenant in the conduct of any business it being
      expressly agreed that the relationship between the parties is, and shall
      at all times remain, that of Landlord and Tenant.

      (c) All amounts payable by Tenant to Landlord under any provision of this
      Lease, other than the Base Rent, shall be deemed to be additional rental
      for the use of the Leased Premises, and Landlord shall have the same
      remedies for the nonpayment of such amounts as for non-payment of other
      rents.

      (d) Where the words "Landlord" and "Tenant" are used in this Lease they
      shall include Landlord and Tenant and shall apply to persons, both men and
      women, associations, partnerships and corporations, and in reading this
      Lease the necessary grammatical changes required to make the provisions
      hereof mean and apply to them shall be made in the same manner as if
      written into the Lease.

      (e) Tenant hereby declares that in entering into this Lease, Tenant relied
      solely upon the statements contained in this Lease and Landlord and Tenant
      both fully understand that no agents or representatives of either Landlord
      or Tenant, respectively, have authority to in any manner change, add to or
      detract from the terms of this Lease.

      (f) The invalidity of one or more of the provisions of this Lease shall
      not affect the remaining portions of this Lease; and, if any one or more
      of the provisions of this Lease should be declared invalid by final order,
      decree or judgment of a court of competent jurisdiction, this Lease shall
      be construed as if such invalid provisions had not been included in this
      Lease.

      (g) Tenant hereby agrees for itself and each succeeding holder of the
      Tenant's interest or any portion thereof under this Lease that any
      judgment, decree or award obtained against the Landlord or any succeeding
      owner of Landlord's interest which is in any manner related to this Lease,
      the Leased Premises, or the Tenant's use and occupancy of the Leased
      Premises or the Building of which the Leased Premises are a part, or the
      land on which such Building is situated, whether at law or in equity,
      shall be satisfied out of Landlord's Property to the extent then owned by
      the Landlord and each such succeeding owner and further agrees to look
      only to such assets and to no other assets of the Landlord or each
      succeeding owner for satisfaction. Neither the Trustees executing this
      Lease not any beneficiaries of such Trust nor any subsequent Landlord
      shall have any personal liability hereunder.

                                       25
<PAGE>

      (h) Force Majeure: Whenever either party hereto is required to do or
      complete any act, matter or thing, the time for doing or completion
      thereof shall be extended by a period of time equal to the number of days
      on or during which party is prevented from, or is unreasonably interfered
      with, the doing or completion of such act, matter or thing because of
      strikes, lock-outs, embargoes, unavailability of labor or materials, wars,
      insurrections, rebellions, civil disorder, declaration of national
      emergencies, acts of God, or other causes beyond such party's reasonably
      control (financial inability excepted); provided, however, nothing
      contained in this subsection shall excuse Tenant from the prompt payment
      of any rental or other charge required of Tenant hereunder except as may
      be expressly provided elsewhere in this Lease. Time is of the essence of
      all forms and provisions of this Lease.

IN WITNESS WHEREOF, the parties hereto have executed this Lease in triplicate,
the original as a sealed instrument, on the day and year first above written.

LANDLORD:                              TENANT:
1050 HINGHAM STREET REALTY TRUST       BIOSPHERE, INC.

By:/s/ ILLEGIBLE                    By: /s/ John M. Carnuccio
-----------------------------        ---------------------------------
   Trustee and not individually
                                    John M. Carnuccio, President & CEO
                                    ----------------------------------
                                            Print Name and Title

Wpa:1050BioSpherelse5.doc

                                       26
<PAGE>

                                   EXHIBIT A1
                                   ----------

                                   LEASE PLAN

                                       27
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                                   EXHIBIT A2
                                   ----------

                                    SITE PLAN

                                       28
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                                    EXHIBIT B
                                    ---------

                               1050 HINGHAM STREET
                              RULES AND REGULATIONS

1.    The regular business hours for the Building shall be from 8:00 a.m. to
      6:00 p.m. Monday through Friday and from 9:00 a.m. to 1:00 p.m. Saturday,
      except customary holidays, as designated by Landlord. Landlord reserves
      the right to exclude from the office portions of the Building, at all
      times other than during such regular business hours, all persons who do
      not present a building pass signed by Landlord. Landlord will furnish
      passes for persons for whom any tenant requests such passes. Tenant shall
      be responsible for all persons for whom it requests such passes and shall
      be liable to Landlord for all wrongful acts of such persons.

2.    The parking areas, driveways, walkways, entrances, passages, courts,
      elevators, vestibules, stairways, corridors or halls of the Building shall
      not be obstructed or encumbered or used for any purpose other than ingress
      and egress to and from the premises demised to any tenant or occupant. All
      loitering is strictly prohibited.

3.    No awnings, antennae or other projections shall be attached to the outside
      walls, windows or roof of the Building without the prior consent of
      Landlord. No curtains, blinds, shades or screens shall be attached or hung
      in, or used in connections with, any window or door of the Leased Premises
      without the prior consent of Landlord. Such awnings, projections,
      curtains, blinds, shades, screens, or other fixtures must be of a quality,
      type, design and color, and attached in a manner, approved by Landlord.

4.    No sign, advertisement, object, notice or other lettering shall be
      exhibited, inscribed, painted or affixed on any part of the outside or
      inside (if visible from outside) of the Leased Premises or of the Building
      without the prior consent of Landlord. Interior signs on doors and
      directory tables, if any, shall be of a size, color and style approved by
      Landlord.

5.    The sashes, sash doors, skylights, windows, transoms and doors that
      reflect or admit light and air into the atrium, halls, passageways or
      other public places in the Building shall not be covered or obstructed,
      nor shall any bottles, parcels, or other articles be placed in any window
      sills.

6.    No show cases or other articles shall be put in front of or affixed to any
      part of the exterior of the Building, nor placed in the halls, corridors,
      vestibules or other parts of the Building except as expressly permitted in
      writing by Landlord.

7.    All waste, rubbish and refuse shall be kept in proper receptacles upon the
      Leased Premises and nothing shall be thrown or swept into or upon the
      corridors, passageways, stairways or other parts of the Building. The
      water and wash closets and other plumbing fixtures shall not be used for
      any purposes other than those for which they were designed and
      constructed, and no sweepings, rubbish, rags or other substances shall be
      thrown therein nor shall water be wasted

                                       29
<PAGE>

      by improper use of faucets, sinks or toilets or otherwise. Tenant shall
      not dispose of any hazardous or toxic materials or substances, as such
      materials or substances may be defined in any applicable federal, state or
      local statute, law, regulation, or ordinance, in or on the Leased
      Premises, or the Building or any fixtures, plumbing or receptacles
      therein. Tenant shall be responsible for any violation of this rule by
      Tenant or Tenant's agents, clerks, invitees or employees.

8.    Tenant shall not mark, paint, drill into, or in any way deface any part of
      the Building or the Leased Premises. No boring, cutting or stringing of
      wires shall be permitted, except with the prior consent of the Landlord,
      and as Landlord may direct. Tenant shall not install any resilient tile or
      similar floor covering in the Leased Premises except in manner approved by
      Landlord.

9.    No bicycles, vehicles or animals of any kind shall be brought into or kept
      in or about the Leased Premises or the Building. Bicycles may be stored in
      racks, if any, furnished for such purpose by Landlord in a common area of
      the Property. No cooking shall be done or permitted in the Building by any
      tenant without the approval of Landlord. Tenant shall not cause or permit
      any unusual or objectionable odors to emanate from the Leased Premises.

10.   Without the prior consent of Landlord, no space in the Building shall be
      used for manufacturing except as specified herein, or for the sale of
      merchandise, goods or property of any kind at auction, fire, bankruptcy,
      going out of business or similar sale.

11.   No additional locks, bolts or other closing or locking devices shall be
      placed upon any of the doors, windows, transoms or other openings by
      Tenant without written permission from the Landlord, and upon termination
      of his leasehold, Tenant shall restore to the Landlord all keys to
      offices, toilets or other rooms furnished to or otherwise procured by
      Tenant. In the event of the loss of any keys furnished by Landlord, Tenant
      shall pay to the Landlord the cost hereof.

12.   All removals from the Building, or the carrying in or out of the Building
      or the Leased Premises of any safes, freight, furniture, or bulky matter
      of any description must take place at such time and in such manner as
      Landlord or its agents may determine, from time to time. If any such
      matter requires special handling, only a person holding a Master Rigger's
      license or otherwise experienced and approved by all appropriate
      authorities for such handling, shall be employed to perform such special
      handling. Tenant shall not place, or permit to be placed, on any part of
      the floor or floors of the Leased Premises a load exceeding the floor load
      per square foot which such floor was designed to carry and which is
      allowed by law. Landlord reserves the right to prescribe the weight and
      position of safes and other heavy matter, which must be placed so as to
      distribute the weight. Landlord reserves the right to inspect all freight
      to be brought into the Building and to exclude from the Building all
      freight which violates any of the Building Rules or the provisions of
      Tenant's lease. Tenant shall pay for all damages caused by such moving.

13.   Tenant shall not use or occupy, or permit any portion of the Leased
      Premises to be used or occupied, as an office for a public stenographer or
      typist, for a barber or manicure shop, or as an employment bureau. Tenant
      shall not engage or pay any employees in the Building, except

                                       30
<PAGE>

      actually working for Tenant in the Building, nor advertise for laborers
      giving any address at the Building.

14.   Tenant, before closing and leaving the Leased Premises at any time, shall
      see that all entrances are locked.

15.   Tenant shall, at its expense, provide artificial light in the Leased
      Premises for Landlord's agents, contractors, and employees while
      performing janitorial or other cleaning services and making repairs or
      alterations in said premises.

16.   The Leased Premises shall not be used, or permitted to be used, for
      lodging or sleeping, or for any immoral or illegal purpose. Canvassing,
      soliciting and peddling in the Building are prohibited and Tenant shall
      cooperate in seeking their prevention.

17.   Tenant shall properly dispose of edible refuse in sealed containers and
      encourage cleanliness among employees to prevent infestation of vermin. If
      the Leased Premises become infested with vermin, Tenant, at its sole cost
      and expense, shall cause Leased Premises to be exterminated from time to
      time, to the satisfaction of the Landlord, and shall employ such
      exterminators therefor as shall be approved by Landlord.

18.   Tenant shall always conduct its operation in the Leased Premises under its
      present trade name, unless Landlord shall otherwise consent in writing.

19.   Tenant shall not use the walkway and parking areas adjacent to the
      Building for business purposes without the prior written consent of the
      Landlord.

20.   Tenant shall receive and deliver goods and merchandise only in the manner,
      at such times, and in such locations as may be reasonably designated by
      Landlord. There shall not be used in any space, or in the common areas of
      the Building any equipment which may damage or deface the Building, either
      by Tenant or by jobbers or others under Tenant's control, in the delivery
      of merchandise or otherwise.

21.   Tenant shall comply with all reasonable requests of Landlord or its agents
      as such requests pertain to safety and security in the Building.

22.   The requirements of Tenant and any complaints of Tenant will be attended
      to by notice to Landlord or upon application at the office of Landlord.
      Employees of Landlord have no authority and shall perform no work or do
      anything outside of the regular duties, unless under special instruction
      of the Landlord.

23.   In order that the good will and reputation of the Building may be
      maintained, no newspaper, magazine or other kind of advertising shall be
      issued by any Tenant wherein any office or other space in the Building is
      given as an address unless Tenant reasonably determined in good faith that
      such advertising could not have any adverse impact on the character of the
      Building or its Landlords.

                                       31
<PAGE>

24.   No Tenant shall do, or permit or suffer anything to be done, on the Leased
      Premises or in the Building which will interfere with the rights,
      privileges and conveniences of any other tenant or which will conflict
      with the provisions of any insurance policy covering the Building or any
      part thereof or which will violate any law, ordinance or rule or
      regulation of any governmental authority.

25.   Landlord reserves the right to rescind, amend or waive any rule or
      regulation at any time prescribed for the Building when, in its judgment,
      it deems it necessary, desirable or proper for its best interest and for
      the best interests of the tenants, and no alteration or waiver of any rule
      or regulation in favor of one tenant shall operate as an alteration or
      waiver in favor of any other tenant. Landlord shall not be responsible to
      any tenant for the non-observance or violation by any other tenant of any
      of the rules or regulations at any time prescribed for the Building.
      Tenant shall conform to all other reasonable rules established by Landlord
      and uniformly applied relative to the operation and use of the Building.

                                       32
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                                    EXHIBIT C
                                    ---------

                               1050 HINGHAM STREET
                      SPECIFICATIONS FOR CLEANING SERVICES

FREQUENCY - Five (5) nights per week, Monday through Friday, except holidays.

WORK  AREA - 1050 Hingham Street Main lobby and floors 1, 2, and 3

I.    GENERAL CLEANING SERVICES

      Nightly
        - Dust sweep flooring with specially treated mops to insure dust-free
            floors.
        - Wash flooring in building entrance foyers.
        - Vacuum carpet areas and rugs.
        - Empty and damp wipe all ashtrays.
        - Empty and damp wipe ashtrays and receptacles in corridors.
        - Clean cigarette urns and replace sand or water as necessary.
        - Empty waste and remove to specific area.
        - Dust office furniture and equipment.
        - Clean and sanitize drinking fountains.
        - Dust counter tops.
        - Vacuum carpeted stairwells.
        - Damp mop and spray buff floors in the lobby.
        - Damp mop and spray buff resilient tile floors. (1/5th of entire area
            to be completed each night.
        - Vacuum carpeting in elevator.
        - Sweep stairs.
        - Clean entrance door glass.
        - Keep service rooms in clean and orderly condition.
        - Clean exposed surfaces in kitchen areas, provided that all utensils
            and kitchen equipment shall be kept clean and removed from such
            surfaces.

      Weekly
        - Dust window sills, ledges and baseboards.
        - Remove finger marks from light switches, door, door frames.
        - Spot-clean glass partition.
        - Damp mop stairs.

      Periodic Cleaning:
        - Strip, seal and refinish all vat floors once per year.

II.   LAVATORY CLEANING SERVICES (Nightly)

                                       33
<PAGE>

        - Sweep and wash flooring with approved germicidal detergent solution.
        - Wash mirrors, powder shelves, bright work, etc. including
            flushometers, piping and toilet seat hinges.
        - Wash both sides of toilet seats, wash basins, bowls and urinals with
            approved germicidal detergent solution.
        - Dust partitions, tile walls, dispensers, doors and receptacles.
        - Empty and clean towel and sanitary disposal receptacles.
        - Remove wastepaper and refuse to a designated area in the premises.
        - Fill toilet tissue, soap and towel dispensers with supplies as
            furnished.

III.  GENERAL CLEANING SERVICES

      Periodic Cleaning:
        - Dust venetian blinds.
        - Accomplish high dusting every three months, which includes the
            following:
        - Dust pictures, frames, charts, graphics and similar wall hangings
            not reached in nightly cleaning.
        - Dust exterior of lighting fixtures.
        - Dust overhead pipes, sprinklers, etc.
        - Dust window frames.
        - Dust vertical surfaces, such as partitions, ventilating louvers,
            etc. not reached in nightly cleaning.
        - Vacuum upholstered furniture every three months.
        - Damp mop corridors and heavy traffic areas nightly.

IV.   LAVATORY CLEANING SERVICES

      Periodic Cleaning
      -     Machine scrub flooring with an approved germicidal detergent
            solution quarterly.
      -     Wash partitions, tile walls and enamel surfaces with an approved
            germicidal solution once a month.
      -     Dust exterior of lighting fixtures once a month.
      -     Accomplish high dusting once a month.

                                       34
<PAGE>

                                    EXHIBIT D
                                    ---------

                    CLARIFICATION OF LIGHT MANUFACTURING USE

Landlord has permitted Tenant to conduct limited research and development and
light manufacturing within the Leased Premises. It is the intention that these
activities be limited, and Tenant hereby provides the following description of
its research and development ("R&D") and limited manufacturing activities
included in the Use of the Leased Premises upon which Landlord's approval is
based.

Tenant is engaged in developing medical applications that incorporate the use of
its plastic particles called microspheres for an emerging category of procedures
called embolotherapy. At the present time, all production activities are
accomplished at its Paris, France facility.

The following describes Tenant's anticipated activities in the short,
intermediate and long-term future:

o     Other than administrative, marketing sales and finance, the Leased
      Premises will be used for only a portion of Tenant's research and
      development ("R & D") activities and none of its manufacturing. These R &
      D activities will involve bench top modeling and testing that incorporates
      standard plastic and metal processing technologies. These are accomplished
      using hand tools or small mechanized or powered tools that generally use
      little power and the process generates little or no heat or noise and no
      volatile, toxic or detectable fumes.

o     Tenant plans to establish a separate manufacturing capability in the
      Leased Premises. This will resemble closely the present manufacturing area
      of the Paris facility. It will be limited to an area of approximately 500
      square feet. This is a highly conditioned "clean room" environment but
      contains little equipment or mechanized tooling. The operations are simple
      chemical operations involving the use of several of the raw material and
      processing components used to manufacture the present product.

o     Tenant will engage in development of complementary products and
      technologies that may include other "particle technologies" that
      incorporate other materials or combinations of materials. This will
      involve some light chemical, mechanical and/or thermal forming processes.
      This will require an expansion of the manufacturing area to a total of
      approximately 1,000 square feet.

o     Almost all of the components used to produce Tenant's product are
      inherently non-toxic or non-hazardous. All handling and disposal will be
      done in accordance with all pertinent local, state or federal regulatory
      standards in effect at the time.

o     All operations conducted in the Leased Premises will be conducted using
      equipment and materials which use little power and generate little or no
      heat or noise and no volatile, toxic or detectable fumes.

                                       35
<PAGE>

o     In the event Tenant proposes to enter into a sublease or assignment of
      this Lease, Landlord shall have the absolute right to withhold its consent
      to any subtenant or assignee which proposes to conduct manufacturing and
      research and development activities in the Leased Premises, unless such
      assignee is a Successor conducting operations substantially identical to
      those conducted by Tenant.

Such activities will be considered within the Use of the Leased Premises if they
otherwise comply with the terms of this lease, including without limitation the
following:

o     All activities, processes, transportation and handling of materials and
      waste are in strict conformance with all environmental, zoning, OSHA, and
      other applicable laws, orders, and conditions, and Tenant provides
      reasonably satisfactory proof of such conformance to Landlord promptly
      upon request.

o     None of such uses require utility, HVAC, floor loading or other physical
      parameters materially beyond those customary in office uses and provided
      in the Building.

o     Activities associated with the use shall not be more intrusive, disruptive
      or materially more demanding of the Property or the Building beyond the
      Leased Premises including, without limitation, use of the loading dock and
      other delivery areas.

o     Such uses will be limited to areas within the Leased Premises reasonably
      acceptable to Landlord, with recognition that the Building shall operate
      as a first class office building, and such uses should be as inapparent as
      possible outside the Leased Premises.

o     Tenant's use shall not materially adversely impact other tenants, the
      operation or facilities of the Property, or the compliance with any law,
      order or condition.

                                       36
<PAGE>

                                   SCHEDULE A

                        LANDLORD'S INITIAL CONSTRUCTION

I. (1) Landlord and Tenant have agreed upon a schematic plan (the "Schematic
Plan") for construction of Landlord's Initial Construction a copy of which is
attached hereto as Exhibit A-1. Landlord shall cause Landlord's Architect to
complete and deliver to Tenant a plan ("Tenant's Plan") consistent with the
Schematic Plan, for the construction of the Leased Premises to prepare for
Tenant's occupancy. Tenant's Plan shall contain all details of Tenant's proposed
improvements to the Leased Premises which are required to permit such
construction by Landlord, including, without limitation, selections of wall
coverings, selection of paint colors, selection of carpeting, door keying
schedule, and the heat factor, if any, of all equipment intended to be used in,
and the human load factor proposed for, each room or other area. Tenant's Plan
shall also include as many requests for pricing of alternatives as Tenant wishes
to consider prior to authorizing Landlord to commence the work pursuant to
Paragraph III below. All of the improvements shown on Tenant's Plan as it is
finally approved by Landlord and Tenant are hereinafter referred to as
"Landlord's Initial Construction." Landlord shall allow Tenant and its agents
and employees access to the Leased Premises at all reasonable times from and
after the date hereof for the purpose of developing Tenant's Plan. Landlord
agrees to reasonably cooperate with Tenant and Tenant's agents, employees and
contractors during the development of Tenant's Plan. Tenant agrees that in order
to prepare Tenant's Plan, Landlord's Architect will need the full cooperation of
Tenant in making decisions with respect to such plan concerning colors, carpets
and other details described above. Tenant shall approve or request modifications
to Tenant's Plan within two (2) business days of receipt from Landlord's
Architect. Tenant agrees to act promptly and within the schedule set forth by
Landlord's Architect for the making of all decisions and approvals required.

      (2) Landlord has contracted with Landlord's Architect for all aspects of
Tenant's Plan which constitute a Building Standard installation, and provided
Tenant uses Landlord's Architect for the preparation of Tenant's Plan, that
portion of the cost of preparation of Tenant's Plan related to a Building
Standard installation shall be paid by Landlord provided that Tenant agrees to
pay to Landlord's Architect promptly after receipt of statements therefore the
cost of completing any part of Tenant's Plan as is not covered by the foregoing
description. The foregoing is intended solely as a benefit to Tenant based upon
Landlord's contractual relationship with Landlord's Architect, and Tenant shall
have no obligation to utilize Landlord's Architect for the preparation of
Tenant's Plan.

      (3) Tenant's Plan shall be subject to Landlord's approval, which Landlord
agrees not to unreasonably withhold or delay. In this connection, any
disapproval or withholding of approval of such Plan by Landlord shall not be
deemed unreasonable if the work designated on such Plan (i) is not in accordance
with the Building Standard or other standards adopted by Landlord consistent
with the terms and conditions of this Lease and timely communicated to Tenant
for construction in the Building, and with all applicable codes and governmental
regulations, including, without limitation, the energy conservation provisions
of the Massachusetts Building Code, (ii) will require the use of contractors of
a type other than those normally engaged by Landlord in the construction of the
Building without Landlord's prior approval, which shall not be unreasonably
withheld or delayed,

                                       37
<PAGE>

(iii) will tend in Landlord's reasonable judgment to delay completion of
Landlord's Initial Construction (as shown on such Plan) beyond the specified
Commencement Date, (iv) is not practicable and consistent with existing physical
conditions in the Building and the plans for the Building which have been filed
with appropriate government authorities, (v) will materially impair Landlord's
ability to perform any of Landlord's obligations under the Lease in the
reasonable judgment of Landlord, (vi) will adversely affect any portion of the
Building other than the Leased Premises or (vii) will exceed the capacity of the
existing feeders or wiring installations serving the Leased Premises.

II. Upon Landlord's and Tenant's approval of Tenant's Plan in accordance with
Paragraph I above, Landlord will promptly negotiate a proposal from a contractor
acceptable to Landlord for Landlord's Initial Construction as shown on Tenant's
Plan including such alternative pricing for any items included in Tenant's Plan
which are beyond the scope of work agreed upon between Landlord and Tenant
("Alternates"). The prices for Alternates specified in Tenant's Plan submitted
by all contractors shall be submitted to Tenant for review forthwith after
receipt.

III. Tenant shall have two (2) business days in which to review such material
concerning Alternates and to approve some alternative combination of work and
the price therefor and to authorize Landlord to commence the work or to
disapprove such work and pricing. The price submitted by the contractor for all
of Landlord's Initial Construction which is in addition to work agreed herein to
be paid for by Landlord (the "Extra Work"), including the price for any
alternative combination of work selected by Tenant pursuant to the preceding
sentence, is hereinafter referred to as "Landlord's Extra Work Price". Any
failure by Tenant to authorize Landlord to perform any element of Landlord's
Initial Construction including any alternative selected as aforesaid within two
(2) business days of submission to Tenant of the material referred to above
shall be deemed a Tenant Delay within the meaning of subparagraph C of Paragraph
V of this Schedule A.

IV. Landlord agrees to construct so much of Landlord's Initial Construction as
constitutes a Building Standard installation as per Schedule A-2 (using
quantities of Building Standard materials necessary to meet the requirements of
Tenant's Plan) at Landlord's sole cost and expense. In addition, Landlord shall
provide glass walls for two conference rooms.

In the event the cost of design and construction of Landlord's Initial
Construction (not including Extra Work) exceeds $140,346, Tenant shall pay to
Landlord the excess cost up to a maximum sum of $31,188 to be defined as
"Tenant's Construction Contribution." Landlord shall be responsible for any
costs in excess of $171,534.00 (not including Extra Work and costs resulting
from Tenant Delays or revisions to Tenant's Plan).

Landlord will also construct Alternates selected by Tenant, the cost of which
shall be borne by Tenant (Extra Work Price). Landlord shall bill all or a
portion of the Extra Work Price and Tenant's Construction Contribution to Tenant
as work progresses. Tenant shall pay all amounts due within ten (10) days.

                                       38
<PAGE>

V.    Completion of Landlord's Initial Construction.

      A.    Landlord's Initial Construction shall be constructed in a good and
            workmanlike manner with reasonable diligence and in accordance with
            applicable laws and codes and Tenant's Plan and related
            specifications, and shall constitute a single non-recurring
            obligation on the part of Landlord. In the event this Lease is
            renewed or extended, for a further term by agreement or by operation
            of law, or if Tenant shall exercise any option to lease or add
            additional rentable area to the Leased Premises, Landlord's
            obligation to perform Landlord's Initial Construction shall not
            apply to any such renewal, extension or expansion.

      B.    In accordance with Section 3 of the Lease, unless it occurs prior to
            the Specified Commencement Date, the date on which Substantial
            Completion of Landlord's Initial Construction in the Initial
            Occupancy Area occurs shall constitute the Commencement Date.
            "Substantial Completion" of Landlord's Initial Construction or words
            of similar import shall mean completion of Landlord's Initial
            Construction exclusive of punch list items, i.e., details of
            construction, mechanical adjustment and decoration, the completion
            of which will not materially interfere with Tenant's use and
            occupancy of the Leased Premises for its normal business purposes
            ("Punch List Items"), including issuance of a certificate of
            occupancy which allows Tenant to occupy the Leased Premises
            provided, however, that if such Substantial Completion has been
            delayed on account of a Tenant Delay (defined below), then
            Substantial Completion shall be deemed to have occurred on the date
            on which Landlord reasonably determined Substantial Completion would
            have occurred but for such Tenant Delay. At any reasonable time,
            after such Substantial Completion following reasonable advance
            notice to Tenant, Landlord may enter the Leased Premises to complete
            such Punch List Items. Landlord shall use reasonable diligence to
            complete such Punch List Items within 60 days thereafter unless such
            item remains incomplete due to lack of availability or for other
            reasons beyond Landlord's control and :Landlord is diligently
            pursuing the resolution of such item, and entry by Landlord, its
            agents, servants, employees or contractors for such purpose shall
            not constitute an actual or constructive eviction, in whole or in
            part, or entitle Tenant to any abatement or diminution of rent, or
            relieve Tenant from and of its obligations under this Lease, or
            impose any liability upon Landlord or its agents by reason of
            inconvenience or annoyance to Tenant, or injury to or interruption
            of Tenant's business, or otherwise.

      C.    In the event Substantial Completion of Landlord's Initial
            Construction shall be delayed by reason of Tenant's delays in
            supplying information, or timely submitting any other plans or
            specifications, or in supplying information, or in approving plans
            or specifications or estimates, or in giving authorizations
            including, without limitation, authorization to proceed with the
            work, or by reason of any changes by Tenant in any designations
            previously made by Tenant pursuant to this Schedule, or by reason of
            any other acts or omissions of Tenant, any such cause shall together
            with other acts referred to in subparagraph (d) of this Paragraph be
            referred to as "Tenant Delays".

                                       39
<PAGE>

      D.    Landlord and Tenant shall cooperate to facilitate the installation
            of cabling, furniture and equipment during the period during which
            Landlord's Initial Construction is in process. Provided that Tenant
            and its employees, agents and contractors do not unreasonably
            interfere with Landlord's Initial Construction, Landlord shall allow
            Tenant access to the Leased Premises for such installations. Prior
            to Tenant's entry into the Leased Premises as permitted hereunder,
            Tenant shall submit a schedule to Landlord (and Landlord's
            contractor, if so requested by Landlord), for their reasonable
            approval, which schedule shall detail the timing and purpose of
            Tenant's entry. Tenant shall hold the Landlord harmless from and
            indemnify and protect and defend Landlord against any loss or damage
            to the Project or Leased Premises and against injury to any person
            caused by Tenant's actions as a result of such entry, to the extent
            such loss or damage is not covered by insurance carried or required
            to be carried under this Lease.

VI.   Alterations.

      No Alterations (as opposed to Landlord's Initial Construction) or
      installations of equipment or otherwise, whether or not constituting an
      Alteration, shall be made or performed by or on behalf of Tenant in the
      Leased Premises prior to the Commencement Date without the prior written
      approval of Landlord, which approval Landlord agrees not to unreasonably
      withhold or delay provided either (i) such work does not impose any
      additional burden on Landlord or Landlord's Contractor and does not
      materially interfere with or delay completion of Landlord's Initial
      Construction, in the reasonable judgment of Landlord, or (ii) Tenant
      agrees to reimburse Landlord for any reasonable cost of such additional
      burden and to treat any resulting delay in Substantial Completion of
      Landlord's Initial Construction as a Tenant Delay. Any such sums billed to
      Tenant in connection with Alterations for services provided by Landlord
      shall be payable by Tenant to Landlord, whether or not the Lease Term
      shall have commenced, within ten (10) days next following the rendition of
      a statement therefore by Landlord to Tenant.

VII.  Estoppel.

      After the Commencement Date, and within ten (10) days next following the
      request of Landlord, Tenant shall deliver to Landlord a written statement
      executed and acknowledged by Tenant, in form reasonably satisfactory to
      the holder of any mortgage of the Property, stating that (i) this Lease is
      then in full force and effect and has not been modified (or, if modified,
      setting forth the specific nature of all modifications), (ii) Tenant has
      accepted the Leased Premises as constructed (iii) the Lease Term has
      commenced, and (iv) the rent payable under this Lease is being paid by
      Tenant on a current basis with no offsets or counterclaims, or if such is
      not the case, stating the correct facts and any reasons therefore if
      applicable.

                                       40
<PAGE>

                                   SCHEDULE B
                                   ----------

                               1050 HINGHAM STREET
                                BUILDING STANDARD

Partitions:
New partitions within office space shall consist of 2 "" metal studs with 5/8"
drywall on both sides. Partitions shall extend six inches above ceiling.

On multi-tenant floors, demising partitions between tenants shall be constructed
as above but shall go to underside of floor above.

Doors and Frames:
3'0" x 7'0" solid core stain grade oak veneer doors with knock-down hollow metal
frames.

Door hardware: 1 " pair butts and one building standard lever handle latch set
with brushed steel finish per door.

Ceilings:
Suspended 2' x 4' texture patterned mineral fiber "second look" acoustical
ceiling tile with exposed recessed grid.

Lighting:
Standard lighting is 2' x 4' fluorescent fixtures with parabolic reflectors.

Switches:
Single pole rocker-type light switches are provided for the purpose of
controlling light fixtures.

Convenience Outlets:
The Landlord will provide Building Standard 120 volt duplex convenience outlets
in partitions.

Telephone Outlets:
The Landlord will provide Building Standard telephone outlets. Outlets shall
include pull string and plaster ring, ready to receive Teflon coated wire.
Devices, plates, wiring and instrument by Tenant.

Wiring:
The Landlord will provide a 120/208 volt tenant panel with 100 amp. main.

Flooring:
The Landlord shall provide a selection of carpet and vinyl tile for Tenant's
consideration. A 4" vinyl base will be utilized on all partitions.

Painting:
The Landlord shall provide painting for all partitions, columns and perimeter
walls within the Tenant Space. Such painting shall consist of one (1)
roller-applied primer coat and one (1) roller

                                       41
<PAGE>

applied finish coat of latex eggshell. Paint colors shall be selected from the
Devoe standard range of colors. No color breaks, dados or special striping or
design shall be provided by Landlord under this Section. The Landlord shall
provide painting for all door frames within the Tenant Space. Such painting
shall consist of two (2) coats of semi-gloss alkyd enamel. Paint colors shall be
selected from the Devoe standard range of colors.

The Landlord shall provide finishing for building standard doors. Such finishing
shall consist of staining and sealing to match the building standard finish.

The Landlord reserves the right to approve the color of all soffits at the
exterior windows of the building, in accordance with samples approved by
Landlord and Landlord's Architect, at their sole discretion.

Sprinklers:

Landlord will provide semi-recessed chrome sprinkler heads as required by
Massachusetts State Building Codes.

Window Treatment:

The Landlord will provide Building Standard horizontal mini-blinds for all
exterior windows.

                                       42<PAGE>
                                                                 Exhibit 10.13.2

                              CONSULTING AGREEMENT

      This CONSULTING AGREEMENT ("Agreement"), made and entered into as of July
1, 1999, by and between NAC RE CORPORATION, a Delaware corporation (the
"Company"), and RONALD L. BORNHUETTER ("Bornhuetter").

      WHEREAS, Bornhuetter has terminated his employment with the Company
effective as of the date hereof; and

      WHEREAS, the Company wishes to continue to avail itself of the services of
Bornhuetter as a Consultant to the Company, and Bornhuetter is willing to
continue to perform services in that capacity on behalf of the Company;

      NOW, THEREFORE, in consideration of the premises and mutual covenants
contained herein and for other good and valuable consideration, the Company and
Bornhuetter (each individually, a "Party," and collectively, the "Parties")
agree as follows:

      1. GENERAL.

      The Company engages Bornhuetter as a consultant for the period as set
forth in Section 2 to provide the services as set forth in Section 3, subject to
the other terms and conditions set forth in this Agreement.

      2. TERM OF SERVICE.

      The term of Bornhuetter's service under this Agreement shall commence as
of July 1, 1999 (the "Effective Date") and shall terminate on the second
anniversary of the Effective Date unless there is an earlier termination of
Bornhuetter's service pursuant to Section 7 (the "Term of Service").

      3. SERVICES.

      During the Term of Service, it is the intention of the Parties that
Bornhuetter serve as a consultant to the Company. As a consultant, Bornhuetter
shall perform such consulting duties and render such advice, including, but not
by way of limitation, duties and advice relating to integration of the Company
with XL Capital Ltd. ("XL") following the Company's merger with a subsidiary of
XL and international reinsurance matters, as the Chief Executive Officer (the
"CEO") of XL may reasonably specify. The CEO may request Bornhuetter to render
such services for up to 20 days per calendar quarter, subject to Bornhuetter's
reasonable convenience and his other business commitments. Bornhuetter shall
serve as a member of the Board of Directors of XL, if appointed thereto, and of
such other boards as may be

<PAGE>

mutually agreed upon by the Parties. Bornhuetter's services shall be rendered in
New York, Connecticut and such other locations as may be mutually agreed upon by
the Parties.

      4. FEES.

      During the Term of Service, Bornhuetter shall receive a base annual fee of
$250,000 (the "Base Annual Fee") payable in 12 monthly installments of
$20,833.33 each at the end of each month, together with any applicable
directors' fees.

      5. BUSINESS EXPENSES.

      (a) DOCUMENTED EXPENSES. Bornhuetter shall be entitled to receive prompt
and full reimbursement for all reasonable business expenses (other than office
and secretarial expenses) incurred by him in rendering services to the Company
under this Agreement, provided that Bornhuetter shall provide documentation of
such expenses in accordance with the usual practices of the Company. Such
reimbursement shall include up to $10,000 per year for expenses related to
Bornhuetter's actuarial society activities.

      (b) OFFICE ALLOWANCE. In addition, the Company shall pay Bornhuetter an
allowance of $10,000 per year for office and secretarial expenses.

      6. INDEPENDENT CONTRACTOR STATUS.

      As a Consultant, Bornhuetter's status shall be that of independent
contractor. Bornhuetter acknowledges that the Company will not withhold any
federal, state or local taxes from the fees to be paid hereunder.

      7. TERMINATION OF SERVICE.

      (a) TERMINATION BY THE COMPANY OTHER THAN DUE TO DEATH, DISABILITY OR FOR
CAUSE. In the event the Company terminates Bornhuetter's service for any reason
other than death, as provided in Section 7(b), Disability, as provided in
Section 7(c), or Cause, as provided in Section 7(d), the Company shall pay to
Bornhuetter the monthly sum of $20,833.33 until June 30, 2001.

      (b) TERMINATION DUE TO DEATH. In the event Bornhuetter's service is
terminated due to his death, the Company shall pay to his designated beneficiary
or other legal representative the monthly installment of the Base Annual Fee for
the month in which Bornhuetter's death occurs, as well as any unreimbursed
business expenses. The Company shall have no further obligation to pay advisory
fees under this Agreement.

      (c) TERMINATION DUE TO DISABILITY. In the event Bornhuetter's service is
terminated due to his Disability, the Company shall pay Bornhuetter the monthly
installment

<PAGE>

of the Base Annual Fee for the month in which termination occurs, as well as any
unreimbursed business expenses. The Company shall have no further obligation to
pay advisory fees under this Agreement. For this purpose, "Disability" shall
mean any physical or mental disability which renders Bornhuetter incapable of
carrying out his duties or responsibilities under this Agreement, provided that
Bornhuetter shall not be considered to have suffered such disability unless he
shall have been unable to carry out such duties or responsibilities for a period
of at least 180 consecutive days. A determination of Disability will be subject
to the certification of a qualified medical doctor appointed by the Company and
reasonably acceptable to Bornhuetter.

      (d) TERMINATION VOLUNTARILY OR FOR CAUSE. In the event Bornhuetter
terminates his service under this Agreement voluntarily or Bornhuetter's service
is terminated by the Company for Cause, the Company shall pay Bornhuetter the
monthly installment of the Base Annual Fee for the month in which termination
occurs, prorated to the date of termination, as well as any unreimbursed
business expenses and the office expense allowance described in Section 5(b),
pro rated to the date of termination. The Company shall have no further
obligation to pay advisory fees under this Agreement. Termination for Cause
shall mean a termination of Bornhuetter's service following his commission of a
felony, a termination because Bornhuetter, in carrying out his duties hereunder,
has engaged in willful gross misconduct resulting in material harm to the
Company, or a termination because Bornhuetter has breached Section 8 or Section
9 of this Agreement. A voluntary termination shall be deemed to include (i) the
failure or refusal by Bornhuetter to accept an appointment to the Board of
Directors of XL or any affiliate of XL or the Company and (ii) Bornhuetter's
resignation from the Board of Directors of XL or from the Board of Directors of
the Company or any affiliate of XL or the Company without the consent of the
Board of Directors of XL.

      8. NON-COMPETITION AND NON-SOLICITATION.

      (a) NON-COMPETE. Bornhuetter shall not engage in competition with the
Company so long as he is serving as a director of XL, the Company or any
affiliate of XL or the Company. Bornhuetter may resign as director at any time,
in which case the provisions of Section 7(d) shall apply. Exception will be made
for his providing actuarial services and for any opportunities for which he
received written consent from the Company. "Competition" shall mean engaging in
any activity for a Competitor, whether as an employee, consultant, officer or
director, or shareholder (except as a less than one percent shareholder of a
publicly traded company) or otherwise. A "Competitor" shall mean any corporation
or other entity which competes with the Company's business, as determined on the
Effective Date. Bornhuetter's actuarial activities shall not be considered a
violation of this Section 8.

      (b) NON-SOLICIT. During the Term of Service, Bornhuetter shall not induce
any employees of the Company, XL or any of their affiliates to terminate their
employment,

<PAGE>

nor shall Bornhuetter solicit or encourage any customers or any corporation or
other entity in a joint venture relationship with the Company, XL or any of
their affiliates, to terminate their or its relationship with the Company, XL or
any of their affiliates or to violate any agreement with any of them.

      (c) TERMINATION OF NON-COMPETE/NON-SOLICIT. The provisions of Sections
8(a) and 8(b) shall terminate upon the earlier to occur of (i) 24 months from
the Effective Date or (ii) Bornhuetter's resignation from the Board of Directors
of XL, the Company, or any affiliate of XL or the Company.

      9. CONFIDENTIAL INFORMATION AND TRADE SECRETS.

      Bornhuetter hereby acknowledges that he has had and in the future may have
access to and become acquainted with various trade secrets and proprietary
information of the Company, XL and their affiliates not available to competitors
of the Company, XL and their affiliates including, without limitation,
information relating to their products, product development, trade secrets,
customers, suppliers, finances, management, operations and business plans and
strategies. Bornhuetter covenants that he will not, directly or indirectly,
disclose or use such information except as is necessary and appropriate in
connection with the rendering by him of services to the Company under this
Agreement or except as may be required by a court of law, a governmental agency
having supervisory authority over the business of the Company or by any
administrative or legislative body (including a committee thereof) with
jurisdiction to order him to divulge, disclose or make accessible such
information; provided, however, that Bornhuetter agrees that, before making such
disclosure, he shall promptly notify the Company and shall cooperate with the
Company in seeking a protective order and/or other appropriate restrictions on
disclosure. All management studies, business or strategic plans and budgets of
or relating to the Company, XL and their affiliates and all notebooks and other
printed, typed or written materials, documents and data containing the
information described in this Section 9 that were furnished to Bornhuetter
during his employment with the Company or are furnished to Bornhuetter in his
capacity as a consultant shall, as between Bornhuetter and the Company, be the
sole and exclusive property of the Company and all of such materials shall be
returned to the Company promptly following the termination of Bornhuetter's
service under this Agreement.

      10. COOPERATION IN LITIGATION.

      Bornhuetter shall cooperate and generally make himself available, subject
to the provisions of Section 3, to give testimony and assistance in connection
with any litigation, arbitration proceeding, government hearing or investigation
involving the Company, XL or any of their affiliates. The Company shall
reimburse Bornhuetter, or advance to him all reasonable expenses incurred in
connection with his testimony, cooperation or assistance under this Section 10.
Such expenses shall include reasonable out-of-pocket travel expenses and

<PAGE>

reasonable fees and disbursements for independent counsel for Bornhuetter, if
Bornhuetter reasonably determines, based on an opinion of counsel furnished to
the Company prior to incurring such fees and expenses, which opinion is
reasonably satisfactory to the Company, that the litigation, arbitration
proceeding, government hearing or investigation is of a nature which requires
that he have independent representation. Such expenses shall be reimbursed or
advanced promptly after Bornhuetter's submission to the Company of statements in
such reasonable detail as the Company may require.

      11. ARBITRATION; EQUITABLE RELIEF.

      Any disputes arising under or in connection with this Agreement shall be
resolved by binding arbitration, to be held in New York, in accordance with the
rules and procedures of the American Arbitration Association. Judgment upon the
award rendered by the arbitrator(s) may be entered in any court having
jurisdiction thereof. Each Party shall bear his or its own costs of the
arbitration or litigation, including, without limitation, his or its attorneys'
fees. Nothing herein shall prevent the Company from seeking equitable relief in
court in connection with any breach or proposed breach by the Executive of the
provisions of Sections 8 and 9. For the purpose of any such equitable relief,
the Executive hereby submits to the exclusive jurisdiction of the courts of the
state of New York and the federal courts of the United States of America located
in such state and hereby waives, and agrees not to assert, as a defense in any
action, suit or proceeding for such equitable relief, that he is not subject
thereto. Executive agrees that service of process in such action, suit or
proceeding shall be deemed in every respect effective service of process upon
him if given in the manner set forth in Section 13 or if effected by any legally
permitted method of service.

      12. ASSIGNMENT.

      This Agreement shall be binding on and inure to the benefit of the Parties
hereto and their respective heirs, personal representatives, successors and
assigns. No rights or obligations of the Company under this Agreement may be
assigned or transferred by the Company except that such rights or obligations
may be assigned pursuant to a merger or consolidation in which the Company is
not the surviving entity, or the sale or liquidation of all or substantially all
of the assets of the Company, provided that the assignee or transferee is the
successor to all or substantially all of the assets of the Company and such
assignee or transferee assumes the liabilities, obligations and duties of the
Company, as contained in this Agreement, either contractually or as a matter of
law. None of Bornhuetter's rights or obligations under this Agreement may be
assigned or transferred by him other than his rights to compensation and
benefits, which may be transferred only by will or operation of law or pursuant
to Section 19 below.

<PAGE>

      13. NOTICE.

      Any written notice required to be given by one Party to the other Party
hereunder shall be deemed effected if delivered by messenger or overnight
courier or mailed by registered mail, return receipt requested:

To the Company at:         One Greenwich Plaza
                           Greenwich, CT  06836-2568
                           Attention:  General Counsel

To Bornhuetter at:         29 Old Stone Bridge Road
                           Cos Cob, CT  06807

or such other address as may be stated in notice given as hereinbefore provided.

      14. GOVERNING LAW.

      The validity, interpretation and performance of this Agreement shall be
governed by the laws of the State of New York, without regard to the principles
of conflicts of law.

      15. SEVERABILITY.

      If any one or more of the provisions contained in this Agreement is held
to be invalid, illegal or unenforceable in any respect, such invalidity,
illegality or unenforceability shall not affect any other provision hereof.

      16. SURVIVORSHIP.

      Wherever appropriate to the intention of the Parties, the respective
rights and obligations of the Parties shall survive any termination or
expiration of the Term of Service.

      17. AMENDMENT/WAIVER.

      No provision in this Agreement may be amended unless such amendment is
agreed to in writing and signed by Bornhuetter and an authorized officer of the
Company. No waiver by either Party of any breach by the other Party of any
condition or provision contained in this Agreement to be performed by such other
Party shall be deemed a waiver of a similar or dissimilar condition or provision
at the same or any prior or subsequent time. Any waiver must be in writing and
signed by Bornhuetter or an authorized officer of the Company, as the case may
be.

<PAGE>

      18. HEADINGS.

      The headings of the sections and subsections contained in this Agreement
are for convenience only and shall not be deemed to control or affect the
meaning or construction of any provision of this Agreement.

      19. BENEFICIARIES.

      Bornhuetter shall be entitled, to the extent permitted under any
applicable law, to select and change a beneficiary or beneficiaries to receive
any compensation or benefit payable hereunder following Bornhuetter's death by
giving the Company written notice thereof. In the event of Bornhuetter's death
or a judicial determination of his incompetence, reference in this Agreement to
Bornhuetter shall be deemed, where appropriate, to refer to his beneficiary,
estate or other legal representative.

      IN WITNESS WHEREOF, the Company has caused this Agreement to be executed
and Bornhuetter has hereunto set his hand as of the day and year first above
written.

                                     NAC RE CORPORATION

                                     By:
                                         ---------------------------------------

                                     -------------------------------------------
                                                 Ronald L. Bornhuetter

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