EXHIBIT 4.2

                  THIS WARRANT HAS NOT BEEN REGISTERED  UNDER THE SECURITIES ACT
OF 1933, AS AMENDED, OR UNDER APPLICABLE STATE SECURITIES LAWS. THIS WARRANT MAY
NOT BE EXERCISED,  SOLD, PLEDGED,  HYPOTHECATED,  TRANSFERRED OR ASSIGNED EXCEPT
UNDER AN EFFECTIVE  REGISTRATION  STATEMENT UNDER SUCH ACT AND APPLICABLE  STATE
SECURITIES LAWS, UNLESS AN EXEMPTION FROM SUCH REGISTRATION IS AVAILABLE AND THE
HOLDER SHALL HAVE  DELIVERED  AN OPINION OF COUNSEL  ADDRESSED TO THE COMPANY TO
SUCH EFFECT; PROVIDED, THAT SUCH OPINION SHALL BE IN FORM AND SUBSTANCE AND FROM
COUNSEL REASONABLY SATISFACTORY TO THE COMPANY.

VOID AFTER 5:00 P.M. NEW YORK TIME, [INSERT EXPIRATION DATE]


Certificate No.                                             Warrant to Purchase
               ------                                  [Insert number of Shares]


Shares of Common Stock

                                  BIOTIME, INC.
                         COMMON SHARE PURCHASE WARRANTS

                  This  certifies  that,  for value  received,  [Insert  name of
Holder] or  registered  assigns  (the  "Holder"),  is entitled to purchase  from
Biotime, Inc. a California  corporation (the "Company"),  at any time after 9:00
A.M., New York time, on [Insert Date of Allowed  Exercise  pursuant to Section 1
of the  Warrant  Agreement  referred  to  below] at a  purchase  price per share
[Insert  Warrant Price  determined  pursuant to Sections 9 and 10 of the Warrant
Agreement] (the "Warrant Price"),  the number of its Common Shares, no par value
per share (the "Common Stock"),  shown above.  The number of shares  purchasable
upon exercise of the Common Share  Purchase  Warrants (the  "Warrants")  and the
Warrant  Price are subject to  adjustment  from time to time as set forth in the
Warrant Agreement referred to below.  Outstand-ing  Warrants not exercised prior
to 5:00 p.m., New York time, on [Insert Expiration Date pursuant to Section 1 of
the Warrant Agreement] shall thereafter be void.

                  Subject to  restriction  specified  in the Warrant  Agreement,
Warrants may be exercised  in whole or in part by  presentation  of this Warrant
Certificate  with the Purchase  Form on the reverse  side hereof duly  executed,
which  signature  shall be  guaranteed by a bank or trust company or a broker or
dealer  which is a member of the National  Association  of  Securities  Dealers,
Inc., and  simultaneous  payment of the Warrant Price (or as otherwise set forth
in Section 10.5) of the Warrant Agreement at the principal office of the Company
(or if a Warrant  Agent is  appointed,  at the  principal  office of the Warrant
Agent).  Payment of such  price  shall be made in cash or by  certified  or bank
cashier's check. As provided in the Warrant Agreement, the Warrant Price and the
number or kind of shares which may be purchased

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upon the exercise of the Warrant evidenced by this Warrant Certificate are, upon
the happening of certain events, subject to modification and adjustment.

                  This Warrant  Certificate  is issued  under and in  accordance
with a Warrant  Agreement dated as of September 13, 1995 between the Company and
Greenbelt  Corp.  and is subject to the terms and  provisions  contained  in the
Warrant  Agreement,  to all of which the Holder of this Warrant  Certificate  by
acceptance of this Warrant Certificate consents. A copy of the Warrant Agreement
may be obtained by the Holder hereof upon written request to the Company. In the
event that  pursuant to Section 13 of the Warrant  Agreement a Warrant  Agent is
appointed and a new warrant  agreement entered into between the Company and such
Warrant  Agent,  then such new warrant  agreement  shall  constitute the Warrant
Agreement for purposes  hereof and this Warrant  Certificate  shall be deemed to
have been issued pursuant to such new warrant agreement.

                  Upon any partial  exercise of the  Warrant  evidenced  by this
Warrant  Certificate,  there shall be issued to the Holder  hereof a new Warrant
Certificate  in respect of the  shares of Common  Stock as to which the  Warrant
evidenced  by this  Warrant  Certificate  shall  not have been  exercised.  This
Warrant  Certificate  may be  exchanged  at the  office of the  Company  (or the
Warrant Agent, if appointed) by surrender of this Warrant  Certificate  properly
endorsed  either  separately  or in  combination  with one or more other Warrant
Certificates  for one or more new Warrant  Certificates  evidencing the right of
the  Holder  thereof  to  purchase  the  aggregate  number  of  shares  as  were
purchasable on exercise of the Warrants evidenced by the Warrant  Certificate or
Certificates exchanged. No fractional shares will be issued upon the exercise of
any  Warrant,  but the Company  will pay the cash value  thereof  determined  as
provided in the Warrant Agreement.  This Warrant  Certificate is transferable at
the office of the Company (or the Warrant Agent, if appointed) in the manner and
subject to the limitations set forth in the Warrant Agreement.

                  The Holder  hereof may be treated by the Company,  the Warrant
Agent (if appointed) and all other persons dealing with this Warrant Certificate
as the  absolute  owner  hereof for any  purpose  and as the person  entitled to
exercise the rights  represented  hereby, or to the transfer hereof on the books
of the  Company,  any  notice to the  contrary  notwithstanding,  and until such
transfer on such books,  the Company (and the Warrant  Agent,  if appointed) may
treat the Holder hereof as the owner for all purposes.

                  Neither the Warrant nor this Warrant Certificate  entitles any
Holder to any of the rights of a stockholder of the Company.

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                  [This Warrant Certificate shall not be valid or obligatory for
any purpose until it shall have been countersigned by the Warrant Agent.]*

DATED:

                  BIOTIME, INC.


(Seal)    By:________________________

                  Title:

                  Attest:____________________

[COUNTERSIGNED:


WARRANT AGENT


By:_________________________]*
          Authorized Signature

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

*         To be part of the  Warrant  only  after the  appointment  of a Warrant
          Agent pursuant to Section 13 of the Warrant Agreement.

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                                  PURCHASE FORM

                    (To be executed upon exercise of Warrant)



To Biotime, Inc.:

                  The  undersigned  hereby  irrevocably  elects to exercise  the
right of purchase  represented  by the within  Warrant  Certificate  for, and to
purchase thereunder,  _____ shares of Common Stock, as provided for therein, and
tenders  herewith payment of the purchase price in full in the form of cash or a
certified or bank cashier's check in the amount of $_________.

                  Please issue a certificate or certificates  for such shares of
Common Stock in the name of, and pay any cash for any fractional share to:

PLEASE INSERT SOCIAL SECURITY        NAME
OR OTHER IDENTIFYING NUMBER          (Please Print Name &
OF ASSIGNEE                           Address)


___________________________    Address

___________________________    Signature

NOTE:             The above signature should correspond exactly with the name on
                  the face of this Warrant Certificate or with the name of the
                  assignee appearing in the assignment form below.

And, if said number of shares shall not be all the shares  purchasable under the
within  Warrant  Certificate,  a new Warrant  Certificate is to be issued in the
name of said  undersigned  for the balance  remaining  of the share  purchasable
thereunder less any fraction of a share paid in cash.

                                        4







                                   ASSIGNMENT

          (To be executed only upon assignment of Warrant Certificate)

                  For value received,  _____________  hereby sells,  assigns and
transfers unto _______________ the within Warrant Certificate, together with all
right, title and interest therein,  and does hereby  irrevocably  constitute and
appoint _________________  attorney, to transfer said Warrant Certificate on the
books of the  within-named  Company,  with  full  power of  substitution  in the
premises.

Dated:___________________                           ____________________________
                             NOTE:    The above signature should correspond
                                      exactly with the name on the face of this
                                      Warrant Certificate.



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