Appendix B

                          MOLECULAR DEVICES CORPORATION
            1995 NON-EMPLOYEE DIRECTORS' STOCK OPTION PLAN ADOPTED ON
                               SEPTEMBER 13, 1995
                            APPROVED BY SHAREHOLDERS
                              ON DECEMBER 12, 1995
                    AMENDED BY THE BOARD ON JANUARY 29, 1999
                 AS AMENDED BY THE STOCKHOLDERS ON MAY 20, 1999


1.       PURPOSE.

         (a) The purpose of the 1995  Non-Employee  Directors' Stock Option Plan
(the "Plan") is to provide a means by which each  director of MOLECULAR  DEVICES
CORPORATION  (the  "Company") who is not otherwise an employee of the Company or
of any Affiliate of the Company (each such person being hereafter referred to as
a "Non-Employee Director") will be given an opportunity to purchase stock of the
Company.

         (b)  The  word  "Affiliate"  as  used  in the  Plan  means  any  parent
corporation or subsidiary  corporation of the Company as those terms are defined
in Sections 424(e) and (f), respectively,  of the Internal Revenue Code of 1986,
as amended from time to time (the "Code").

         (c) The Company,  by means of the Plan, seeks to retain the services of
persons now serving as  Non-Employee  Directors  of the  Company,  to secure and
retain the  services  of persons  capable  of serving in such  capacity,  and to
provide  incentives for such persons to exert maximum efforts for the success of
the Company.

2.       ADMINISTRATION.

         (a) The Plan shall be  administered  by the Board of  Directors  of the
Company (the "Board") unless and until the Board delegates  administration  to a
committee, as provided in subparagraph 2(b).

         (b) The Board may  delegate  administration  of the Plan to a committee
composed  of not fewer than two (2) members of the Board (the  "Committee").  If
administration  is  delegated  to a  Committee,  the  Committee  shall have,  in
connection with the administration of the Plan, the powers theretofore possessed
by the Board, subject,  however, to such resolutions,  not inconsistent with the
provisions of the Plan, as may be adopted from time to time by the Board. If the
Committee is delegated  authority to amend or fix the timing or terms of options
granted under the Plan,  then the composition of the Committee shall comply with
the  requirements for exemption of option grants from the application of Section
16 of the Securities Exchange Act of 1934, or the terms of such options shall be
such as to qualify  such options for such  exemption.  The Board may abolish the
Committee at any time and revest in the Board the administration of the Plan.

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3.       SHARES SUBJECT TO THE PLAN.

         (a) Subject to the  provisions of paragraph 10 relating to  adjustments
upon changes in stock,  the stock that may be sold  pursuant to options  granted
under the Plan  shall not  exceed in the  aggregate  three  hundred  forty-seven
thousand five hundred  (347,500)  shares of the Company's  common stock.  If any
option granted under the Plan shall for any reason expire or otherwise terminate
without having been exercised in full, the stock not purchased under such option
shall again become available for the Plan.

         (b) The stock subject to the Plan may be unissued  shares or reacquired
shares, bought on the market or otherwise.

4.       ELIGIBILITY.

         (a) Options  shall be granted  only to  Non-Employee  Directors  of the
Company.

5.       NON-DISCRETIONARY GRANTS.

         (a) Upon the date of the initial approval of the Plan by the Board (the
"Adoption Date"), each person who is then a Non-Employee Director  automatically
shall be granted an option to purchase  sixteen  thousand five hundred  (16,500)
shares of common  stock of the  Company  on the terms and  conditions  set forth
herein.

         (b) Each person who is, after the Adoption Date,  elected for the first
time to be a Non-Employee  Director  automatically  shall,  upon the date of his
initial  election to be a Non-Employee  Director by the Board or shareholders of
the Company,  be granted an option to purchase ten thousand  (10,000)  shares of
common stock of the Company on the terms and conditions set forth herein.

         (c) Following  the Adoption  Date,  each  Non-Employee  Director  shall
automatically be granted an additional  Option to purchase four thousand (4,000)
shares of common  stock of the  Company  on the terms and  conditions  set forth
herein immediately following each annual meeting of stockholders.

         (d) Notwithstanding  anything to the contrary set forth in this Section
5, each Non-Employee Director who received a stock option grant pursuant to this
Plan in  September  1998 (a  "September  1998  Grant")  shall not be entitled to
future  grants under this Plan until the  September  1998 Grant shall have fully
vested. On the date that the September 1998 Grant shall have fully vested,  such
Non-Employee  Director shall be treated as having been initially elected to be a
Non-Employee  Director on such date and receive the stock option  referenced  in
Section  5(b) and,  thereafter,  shall be eligible to receive the stock  options
referenced in Section 5(c).

6.       OPTION PROVISIONS.

         Each option shall be subject to the following terms and conditions:

         (a) The term of each option  commences  on the date it is granted  and,
unless sooner  terminated as set forth herein,  expires on the date ("Expiration
Date")  ten (10) years from the

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date of grant. If the optionee's service as a Non-Employee  Director or employee
of or consultant to the Company or any  Affiliate  terminates  for any reason or
for no reason,  the option shall terminate on the earlier of the Expiration Date
or the date  three (3)  months  following  the date of  termination  of all such
service;  provided,  however,  that if such termination of service is due to the
optionee's  death,  the option shall  terminate on the earlier of the Expiration
Date or eighteen (18) months following the date of the optionee's  death. In any
and all circumstances,  an option may be exercised following  termination of the
optionee's  service as a  Non-Employee  Director or employee of or consultant to
the Company or any Affiliate only as to that number of shares as to which it was
exercisable  on the date of termination of such all service under the provisions
of subparagraph 6(e).

         (b) Subject to  subparagraph  4(b),  the exercise  price of each option
shall be one  hundred  percent  (100%)  of the fair  market  value of the  stock
subject to such option on the date such option is granted.

         (c) Payment of the exercise price of each option is due in full in cash
upon any exercise when the number of shares being  purchased  upon such exercise
is less than 1,000 shares; but when the number of shares being purchased upon an
exercise is 1,000 or more shares,  the optionee may elect to make payment of the
exercise price under one of the following alternatives:

             (i) Payment of the exercise price per share in cash at the time of

exercise; or

             (ii) Provided that at the time of the exercise the Company's common
stock is  publicly  traded  and quoted  regularly  in the Wall  Street  Journal,
payment by delivery of shares of common  stock of the Company  already  owned by
the  optionee,  held for the period  required to avoid a charge to the Company's
reported earnings,  and owned free and clear of any liens, claims,  encumbrances
or  security  interest,  which  common  stock shall be valued at its fair market
value on the date preceding the date of exercise; or

             (iii) Payment by a combination of the methods of payment  specified
in subparagraph 6(c)(i) and 6(c)(ii) above.

         Notwithstanding the foregoing, this option may be exercised pursuant to
a program  developed  under  Regulation T as promulgated by the Federal  Reserve
Board which  results in the  receipt of cash (or check) by the Company  prior to
the issuance of shares of the Company's common stock.

         (d) An option shall not be  transferable  except by will or by the laws
of  descent  and  distribution,  or  pursuant  to  a  domestic  relations  order
satisfying the requirements of Rule 16a-12 under the Securities  Exchange Act of
1934 (a "DRO") and shall be  exercisable  during the  lifetime  of the person to
whom the option is granted  only by such  person  (or by his  guardian  or legal
representative) or transferee pursuant to a DRO.  Notwithstanding the foregoing,
the  optionee  may,  by  delivering  written  notice  to the  Company  in a form
satisfactory  to the  Company,  designate a third party who, in the event of the
death of the optionee, shall thereafter be entitled to exercise the option.

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         (e) The option shall become  exercisable in installments  over a period
of four years from the date of grant in equal annual installments  commencing on
the date one year  after  the  date of grant of the  option,  provided  that the
optionee has, during the entire period prior to such vesting date,  continuously
served as a Non-Employee Director or employee of or consultant to the Company or
any  Affiliate  of  the  Company,  whereupon  such  option  shall  become  fully
exercisable  in  accordance  with its terms with  respect to that portion of the
shares  represented  by that  installment.  For  purposes of vesting  under this
subparagraph  6(e),  attendance  at no less than  two-thirds  (2/3) of the Board
meetings  occurring  during an  installment  period is  required in order for an
optionee  serving  as a  Non-Employee  Director  to vest for  such  installment;
failure to satisfy this  requirement  during any particular  installment  period
shall result in an abatement of the vesting of the option during the  applicable
installment  period and the  aggregate  vesting  period of such option  shall be
increased by one additional year.

         (f) The  Company may  require  any  optionee,  or any person to whom an
option is transferred under  subparagraph 6(d), as a condition of exercising any
such option:  (i) to give written  assurances  satisfactory to the Company as to
the optionee's  knowledge and experience in financial and business matters;  and
(ii) to give written  assurances  satisfactory  to the Company stating that such
person is  acquiring  the stock  subject  to the option  for such  person's  own
account and not with any present intention of selling or otherwise  distributing
the  stock.  These  requirements,  and any  assurances  given  pursuant  to such
requirements,  shall be  inoperative  if (i) the issuance of the shares upon the
exercise  of the option  has been  registered  under a  then-currently-effective
registration  statement  under  the  Securities  Act of 1933,  as  amended  (the
"Securities Act"), or (ii), as to any particular requirement, a determination is
made by counsel for the  Company  that such  requirement  need not be met in the
circumstances under the then-applicable securities laws.

         (g)  Notwithstanding  anything to the  contrary  contained  herein,  an
option may not be exercised  unless the shares  issuable  upon  exercise of such
option are then  registered  under the Securities Act or, if such shares are not
then so registered,  the Company has determined  that such exercise and issuance
would be exempt from the registration requirements of the Securities Act.

7.       COVENANTS OF THE COMPANY.

         (a) During the terms of the options granted under the Plan, the Company
shall  keep  available  at all times the number of shares of stock  required  to
satisfy such options.

         (b) The Company shall seek to obtain from each regulatory commission or
agency having  jurisdiction  over the Plan such  authority as may be required to
issue and sell shares of stock upon  exercise of the options  granted  under the
Plan; provided,  however, that this undertaking shall not require the Company to
register  under the Securities Act either the Plan, any option granted under the
Plan,  or any stock issued or issuable  pursuant to any such  option.  If, after
reasonable  efforts,  the Company is unable to obtain  from any such  regulatory
commission or agency the authority which counsel for the Company deems necessary
for the lawful  issuance and sale of stock under the Plan,  the Company shall be
relieved from any liability for failure to issue and sell stock upon exercise of
such options.

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8.       USE OF PROCEEDS FROM STOCK.

         Proceeds from the sale of stock  pursuant to options  granted under the
Plan shall constitute general funds of the Company.

9.       MISCELLANEOUS.

         (a) Neither an optionee nor any person to whom an option is transferred
under  subparagraph  6(d) shall be deemed to be the holder of, or to have any of
the rights of a holder with respect to, any shares subject to such option unless
and until such person has satisfied all  requirements for exercise of the option
pursuant to its terms.

         (b) Nothing in the Plan or in any instrument  executed pursuant thereto
shall confer upon any Non-Employee Director any right to continue in the service
of the Company or any  Affiliate or shall  affect any right of the Company,  its
Board  or  stockholders  or  any  Affiliate  to  terminate  the  service  of any
Non-Employee Director with or without cause.

         (c) No Non-Employee  Director,  individually or as a member of a group,
and no beneficiary or other person claiming under or through him, shall have any
right,  title or interest in or to any option  reserved  for the purposes of the
Plan  except as to such  shares  of common  stock,  if any,  as shall  have been
reserved for him pursuant to an option granted to him.

         (d) In connection  with each option made pursuant to the Plan, it shall
be a condition precedent to the Company's obligation to issue or transfer shares
to a Non-Employee  Director,  or to evidence the removal of any  restrictions on
transfer, that such Non-Employee Director make arrangements  satisfactory to the
Company  to insure  that the  amount of any  federal  or other  withholding  tax
required to be withheld  with respect to such sale or transfer,  or such removal
or lapse, is made available to the Company for timely payment of such tax.

             (i) If the common stock is listed on any established stock exchange
or a national market system,  including  without  limitation the National Market
System  of the  National  Association  of  Securities  Dealers,  Inc.  Automated
Quotation  ("Nasdaq")  System,  the Fair Market Value of a share of common stock
shall be the closing sales price for such stock (or the closing bid, if no sales
were  reported) as quoted on such system or exchange  (or the exchange  with the
greatest volume of trading in common stock) on the last market trading day prior
to the day of  determination,  as reporting  in the Wall Street  Journal or such
other source as the Board deems reliable;

             (ii) If the common stock is quoted on the Nasdaq System (but not on
the  National  Market  System  thereof) or is  regularly  quoted by a recognized
securities dealer but selling prices are not reported,  the Fair Market Value of
a share of common  stock shall be the mean  between the bid and asked prices for
the  common  stock  on  the  last  market  trading  day  prior  to  the  day  of
determination,  as reported in the Wall Street  Journal or such other  source as
the Board deems reliable;

             (iii) In the absence of an established market for the common stock,
the Fair Market Value shall be determined in good faith by the Board.

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10.      ADJUSTMENTS UPON CHANGES IN STOCK.

         (a) If any change is made in the stock  subject to the Plan, or subject
to  any  option   granted  under  the  Plan  (through   merger,   consolidation,
reorganization,  recapitalization,  stock  dividend,  dividend in property other
than cash, stock split, liquidating dividend, combination of shares, exchange of
shares,  change in corporate  structure or otherwise),  the Plan and outstanding
options will be  appropriately  adjusted in the class(es) and maximum  number of
shares  subject to the Plan and the class(es) and number of shares and price per
share of stock subject to outstanding options.

         (b) In the event of: (1) a merger or consolidation in which the Company
is not the surviving  corporation;  (2) a reverse merger in which the Company is
the  surviving  corporation  but  the  shares  of  the  Company's  common  stock
outstanding  immediately  preceding  the merger are  converted  by virtue of the
merger  into  other  property,  whether  in the  form  of  securities,  cash  or
otherwise;  or (3) any other  capital  reorganization  in which  more than fifty
percent (50%) of the shares of the Company  entitled to vote are exchanged,  the
time during which options  outstanding  under the Plan may be exercised shall be
accelerated and the options terminated if not exercised prior to such event.

11.      AMENDMENT OF THE PLAN.

         (a) The Board at any time,  and from time to time,  may amend the Plan,
provided,  however,  that  except  as  provided  in  paragraph  10  relating  to
adjustments  upon  changes in stock,  no  amendment  shall be  effective  unless
approved by the  stockholders of the Company within twelve (12) months before or
after the adoption of the amendment, where the amendment will:

             (i)  Increase  the number of shares  which may be issued  under the
Plan;

             (ii) Modify the requirements as to eligibility for participation in
the Plan (to the extent such modification requires stockholder approval in order
for the Plan to comply with the requirements of Rule 16b-3); or

             (iii)  Modify  the  Plan  in any  other  way if  such  modification
requires  stockholder  approval  in  order  for the  Plan  to  comply  with  the
requirements  of Nasdaq or any securities  exchange on which the Company desires
prices for its common stock to be quoted.

         (b)  Rights  and  obligations  under  any  option  granted  before  any
amendment  of the Plan shall not be  impaired by such  amendment  unless (i) the
Company  requests  the  consent of the person to whom the option was granted and
(ii) such person consents in writing.

12.      TERMINATION OR SUSPENSION OF THE PLAN.

         (a) The Board may suspend or terminate the Plan at any time. No options
may be  granted  under  the  Plan  while  the Plan is  suspended  or after it is
terminated.

         (b) Rights and  obligations  under any option granted while the Plan is
in effect shall not be impaired by suspension or termination of the Plan, except
with the consent of the person to whom the option was granted.

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         (c) The Plan shall  terminate  upon the occurrence of any of the events
described in subparagraph 10(b) above.

13.      EFFECTIVE DATE OF PLAN; CONDITIONS OF EXERCISE.

         (a) The Plan  shall  become  effective  upon  adoption  by the Board of
Directors,  subject to the condition subsequent that the Plan is approved by the
stockholders of the Company.

         (b) No option  granted under the Plan shall be exercised or exercisable
unless and until the condition of subparagraph 13(a) above has been met.


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