SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D
          Under the Securities Exchange Act of 1934 (Amendment No. 4)*


                                  BioTime, Inc.
 ................................................................................
                                (Name of Issuer)

                           Common Shares, no par value
 ................................................................................
                         (Title of Class of Securities)

                                    09066L105
 ................................................................................
                                 (CUSIP Number)

                                 Harold D. Waitz
          935 Pardee Street, Berkeley, California 94710; (510) 845-9535
 ................................................................................
 (Name, Address and Telephone Number of Person Authorized to Receive Notices 
                              and Communications)

                               September 16, 1997
 ................................................................................
              (Date of Event which Requires Filing this Statement)

If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  which is the subject of this  Schedule 13D, and is filing this
schedule because of Rule 13d-1(b)(3) or (4), check the following box [ ].

Note: Six copies of this statement, including all exhibits, should be filed with
the  Commission.  See Rule  13d-1(a) for other  parties to whom copies are to be
sent.

*The  remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for  any  subsequent   amendment   containing   information  which  would  alter
disclosures provided in a prior cover page.






CUSIP No. 09066L105

         1)       Names of Reporting Persons S.S. or I.R.S. Identification Nos.
                  of Above Persons
                           Harold D. Waitz

         2)       Check the Appropriate Box if a Member of a Group 
                  (See Instructions)
                                                                        (a) [ ]
                                                                        (b) [ ]
         3)       SEC Use Only

         4)       Source of Funds (See Instructions)
                           PF; OO

         5)       Check if Disclosure of Legal Proceedings is Required Pursuant
                  to Items 2(d) or 2(e)                                     [ ]

         6)       Citizenship or Place of Organization
                           U.S.A.

                  7)       Sole Voting Power
Number of                           167,069
Shares
Beneficially      8)       Shared Voting Power
Owned by                            0
Each
Reporting         9)       Sole Dispositive Power
Person With                         167,069

                  10)      Shared Dispositive Power
                                    0

         11)      Aggregate Amount Beneficially Owned by Each Reporting Person
                           167,069

         12)      Check if the Aggregate Amount in Row (11) Excludes Certain 
                  Shares (See Instructions)                                 [ ]

         13)      Percent of Class Represented by Amount in Row (11)
                           5.1%

         14)      Type of Reporting Person (See Instructions)
                           IN

                               Page 2 of 14 Pages






Item 1.  Security and Issuer

         The class of equity securities to which this schedule relates is Common
Shares,  no par value (the  "Common  Shares"),  of BioTime,  Inc.,  a California
corporation (the "Company").  The Company has its principal executive offices at
935 Pardee Street, Berkeley, California 94710.

         This  schedule  is  being  filed  pursuant  to  Section  13(d)  of  the
Securities  Exchange Act of 1934, as amended (the "Exchange  Act") and the rules
and regulations promulgated thereunder.

Item 2.  Identity and Background

(a)      The name of the person filing this schedule is Harold D. Waitz.

(b)      The business address of Harold D. Waitz is 935 Pardee Street, Berkeley,
         California 94710.

(c)      Harold D. Waitz is currently the Vice President of Engineering of 
         BioTime, Inc., 935 Pardee Street, Berkeley, California 94710.

(d)      Harold D. Waitz has not been convicted during the last five years in a 
         criminal proceeding, excluding traffic violations or similar 
         misdemeanors.

(e)      Harold D. Waitz has not been a party  during the last five years to any
         civil  proceeding  of a judicial or  administrative  body of  competent
         jurisdiction,  and has not,  as a  result  of such a  proceeding,  been
         subject  to  a  judgment,   decree  or  final  order  enjoining  future
         violations  of, or  prohibiting  or  mandating  activities  subject to,
         federal or state  securities laws or finding any violation with respect
         to such laws.

(f)      Harold D. Waitz is a citizen of the United States of America.

Item 3.  Source and Amount of Funds or Other Consideration

         The  source of funds  used by Harold D.  Waitz to  purchase  his Common
Shares includes both personal funds and borrowed funds.

         Mr. Waitz has executed a Customer Agreement with Montgomery  Securities
and a related  Representation Letter for the purpose of borrowing  approximately
$193,620 to exercise certain incentive stock options (through which he purchased
21,000  Common  Shares  at  a  price  of  $9.22  per  share)  and  approximately
$352,803.31  to refinance  certain  margin loans  obtained  from CS First Boston
during  February 1997 in connection  with Mr. Waitz's  exercise of  subscription
rights that were  distributed by the Company pro rata to its  shareholders.  Mr.
Waitz has pledged all of his Common Shares as collateral  for such loans and has
agreed not to sell any Common Shares of

                               Page 3 of 14 Pages





the Company while his margin loan is secured by his Common Shares. A copy of the
aforesaid Customer Agreement and Representation  Letter are filed as Exhibits to
this Schedule 13D and are incorporated herein by reference.


Item 4.  Purpose of Transaction

         These  securities were purchased for investment.  Mr. Waitz may acquire
additional  Common  Shares or sell all or some of his Common  Shares  based upon
market and economic circumstances.

         Mr. Waitz is the Vice President of  Engineering of the Company,  and is
also a director of the Company.  In his capacity as an officer and director,  he
will participate in the management of the Company.

         Mr. Waitz does not have any current plans or proposals  which relate to
or would result in (i) an extraordinary corporate transaction, such as a merger,
reorganization  or  liquidation  of the  Company;  (ii) a sale or  transfer of a
material amount of assets of the Company;  (iii) any change in the present board
of directors or management  of the Company,  including any plans or proposals to
change the number or term of directors or to fill any existing  vacancies on the
board; (iv) any material change in the present capitalization or dividend policy
of the  Company;  (v) any other  material  change in the  Company's  business or
corporate structure;  (vi) any change in the Company's Articles of Incorporation
or Bylaws or other  action  which may impede the  acquisition  of control of the
Company by any person; (vii) causing any class of the Company's securities to be
delisted from a national  securities exchange or to cease to be authorized to be
quoted in an inter-dealer  quotation system of a registered  national securities
association; (viii) any of the Company's equity securities becoming eligible for
termination of registration pursuant to Section 12(g)(4) of the Exchange Act; or
(ix) any action similar to any of those enumerated above.

Item 5.  Interest in Securities of the Issuer

         (a)  Harold  D.  Waitz  directly  owns  167,069  Common  Shares,  which
constitute  approximately 5.1% of the  3,266,193  Common Shares  outstanding  on
September 17, 1997. The forgoing  number of  outstanding  Common Shares is based
upon information provided by the Company.

         (b) Mr.  Waitz has the sole power to vote and to direct  the vote,  and
the sole power to dispose  and to direct the  disposition,  with  respect to the
shares held in his name.

         (c) On or about September 16, 1997, Mr. Waitz  purchased  21,000 Common
Shares through the exercise of an incentive stock option at a price of $9.22 per
share.


                               Page 4 of 14 Pages





         (d) Mr.  Waitz has the sole power to vote and to direct  the vote,  and
the sole power to dispose  and to direct the  disposition,  with  respect to the
shares held in his name.  No other  person is known to have the right to receive
or the power to direct the receipt of dividends  from,  or the proceeds from the
sale of, his Common Shares.

Item 6.  Contracts, Arrangements, Understandings or Relationships with Respect
         to Securities of the Issuer

         Harold D. Waitz has no  agreements  with  respect to (a) voting  Common
Shares  held in his  name,  (b)  acquiring  additional  Common  Shares,  and (c)
disposing of Common Shares held in his name.


Item 7.  Material to Be Filed as Exhibits

(a)      Customer Agreement between Harold D. Waitz and Montgomery Securities

(b)      Representation Letter from Harold D. Waitz to Montgomery Securities


Signature


         After reasonable inquiry and to the best of my knowledge I certify that
the information set forth in the statement is true, complete and correct.

                                             /s/: Harold D. Waitz
Dated:  September 24, 1997                 ____________________________________
                                             Harold D. Waitz




                                     Page 5 of 14 Pages



                                                                    Exhibit (a)
MONTGOMERY SECURITIES


                               CUSTOMER AGREEMENT

  This  agreement  sets  forth the terms and  conditions  pursuant  to which we,
Montgomery  Securities,  and our  successors  and assigns,  will  maintain  your
account for purchases and sales of "securities and other property," which means,
but is not limited to securities,  financial instruments,  commodities and money
of every kind and nature and related  contracts  and  options.  This  definition
includes  securities or other property  currently or hereafter held,  carried or
maintained  by, or in the  possession  or control  of, us or any of our  related
entities for any purpose in and for any account now or hereafter  opened by you.
You  understand  that,  if your account is a cash  account,  the  provisions  of
paragraphs  18 & 19 are not  binding  upon you  unless  you enter  into a margin
transaction  and, if your account is a commodities  account,  the  provisions of
paragraph 14 shall not be applicable.

1.    APPLICABLE LAW AND REGULATIONS.  All transactions in your account shall be
      subject  to all  applicable  laws and the  rules  and  regulations  of all
      federal, state and self-regulatory  agencies,  including,  but not limited
      to,  the  Board  of  Governors  of the  Federal  Reserve  System  and  the
      constitution, rules, customs and usages of the exchange or market (and its
      clearing house) where the transactions are executed.

2.    SECURITY  INTEREST AND LIEN. All securities or other property which we may
      at any time be carrying or maintaining for you or which may at any time be
      in our possession or control for any purpose, including safekeeping, shall
      be subject to a general lien for the discharge of all of your  obligations
      to us,  irrespective of whether or not we have made advances in connection
      with such securities or other property,  and irrespective of the number of
      accounts you may have with us.

3.    DEPOSITS ON CASH  TRANSACTIONS.  If at any time  Montgomery  Securities
      considers  it  necessary  for  its  protection,  it may in its  discretion
      require you to deposit  cash or  collateral  in your account to assure due
      performance by you of your open contractual commitments.

4.    BREACH OR DEFAULT.  In the event of any breach by you of any  agreement
      with us, or any default by you in any  obligation to us, or should you die
      or file a petition in bankruptcy or for the  appointment  of a receiver by
      or against you, or should we for any reason  whatsoever  deem it necessary
      for our protection,  we are hereby authorized,  at our discretion, to sell
      any or all of the  securities  and other  property in any of your accounts
      which may be in our possession or control,  or which we may be carrying or
      maintaining for you (either  individually  or jointly with others),  or to
      buy-in any  securities or other property of which your account or accounts
      may be short,  or to cancel any other standing  orders,  to close out your
      account  or  accounts  in whole  or in part or in  order to close  out any
      commitment  made on your behalf.  Any such sale,  purchase or cancellation
      may be made according to our judgment and may be made, at our  discretion,
      on the  exchange  or other  market  where such  business  is then  usually
      transacted,  or at public auction or at private sale, without  advertising
      the same and without notice to you or to your personal representative, and
      without  prior  tender,  demand or call of any kind upon you, or upon your
      personal representative (each of which is expressly waived by you), and we
      may  purchase  the  whole  or any part  thereof  free  from  any  right of
      redemption,  and you shall  remain  liable  for any  deficiency;  it being
      understood that a prior tender,  demand,  call or notice of any kind shall
      not be  considered  a waiver  of our  right to sell or buy any  securities
      and/or  other  property  held by us,  or owed  us by you,  at any  time as
      hereinbefore  provided.  Nothing in this  agreement  shall be construed as
      relieving you of any obligations imposed by law.

5.    FINALITY OF REPORTS.  Reports of execution of orders and  statements of
      your accounts shall become  conclusive if not objected to in writing,  the
      former within five days, and the latter within ten days,  after forwarding
      by us to you by mail or otherwise.

                               Page 6 of 14 Pages






6.    RECEIPT OF TRUTH-IN-LENDING.  You hereby acknowledge receipt and review of
      Montgomery  Securities'  Truth-in-Lending  disclosure  statement contained
      here within.  You  understand  that  interest will be charged on any debit
      balances in accordance with the methods  described in that statement or in
      any  amendment  or  revision  thereto  which may be provided to you. It is
      understood and agreed that the interest charge made to your account at the
      close of one charge period will be compounded,  unless paid;  that is, the
      unpaid interest  charge for previous  periods will be added to the opening
      balance for the next charge period, thereby becoming part of the principal
      amount due and bearing like interest.

7.    TRANSFERS BETWEEN  ACCOUNTS.  At any time and from time to time, at our
      discretion,  we may without notice to you apply and/or transfer any or all
      securities and/or other property of yours  interchangeably  between any of
      your accounts.

8.    SELL ORDERS.  It is understood and agreed that you will designate any sell
      order for a short  account  which you place with us as a "short  sale" and
      hereby authorize us to mark such order as being "short",  and when placing
      with us any order for a long account, will designate it as such and hereby
      authorize us to mark such order as being  "long." Any sell order which you
      shall  designate  as being  for long  account  as  above  provided  is for
      securities  then  owned  by you  and,  if such  securities  are  not  then
      deliverable  by us from any of your  accounts,  the  placing of such order
      shall constitute a representation  by you that it is impracticable for you
      to then  deliver such  securities  to us but that you will deliver them as
      soon as it is possible  for you to do so without  undue  inconvenience  or
      expense.

9.    AGE, BENEFICIAL INTEREST. If you are an individual, you represent that you
      are of full legal age, and, in any event not less than  eighteen  years of
      age. You further  represent that no one except you has an interest in your
      account with us.

10.   OPERATIONAL MATTERS. Montgomery Securities primarily uses banks located in
      California and New York to issue checks. Also, when we hold securities for
      your account,  dividends and interest are credited on or about the payable
      date as received. Most of our customers prefer to have these funds held in
      their  accounts,  and this will be the procedure which we will follow with
      your account  unless you advise us of an alternative  procedure  which you
      would prefer.  For example,  we could arrange for checks to be sent to you
      monthly. If you require special  arrangements,  please bring the matter to
      our   attention.   Montgomery   Securities'   policy  is  not  to  receive
      remuneration for directing orders to particular  brokers/dealers or market
      centers for  execution.  Notwithstanding  this policy,  should  Montgomery
      Securities  receive  such  remuneration  on any  transaction,  appropriate
      disclosure will be made.

11.   CREDIT REPORT.  Montgomery  Securities may, in its discretion,  request an
      investigative  consumer report on you as a credit reference,  which report
      may include  information  with respect to character,  general  reputation,
      personal  characteristics  and mode of living. In accordance with the Fair
      Credit Reporting Act, a copy of any such report, if obtained, will be made
      available to you upon written request.

12.   CLEARANCE  ACCOUNTS.  If  Montgomery  Securities  carries  your account as
      clearing broker by arrangement  with another broker through whose courtesy
      your  account  has been  introduced,  then  unless  Montgomery  Securities
      receives from you a written notice to the contrary,  Montgomery Securities
      shall accept from such other broker,  without any inquiry or investigation
      by us,  (i)  orders  for the  purchase  and sale of  securities  and other
      property  on  margin  or  otherwise,   and  (ii)  any  other  instructions
      concerning said account. You understand  Montgomery  Securities shall have
      no  responsibility  or  liability to you for any acts or omissions of such
      other broker, its officers, employees or agents.

13.   WAIVER, ASSIGNMENT AND NOTICES. No term or provision of this Agreement may
      be waived or modified  unless in writing  and signed by the party  against
      whom such  waiver or  modification  is sought to be  enforced.  Montgomery
      Securities' failure to insist at any time upon strict compliance with this
      Agreement or with any of the

                               Page 7 of 14 Pages





      terms hereunder or any continued  course of such conduct on its part shall
      in no event constitute or be considered a waiver by Montgomery  Securities
      of any of its rights or  privileges.  This  Agreement  contains the entire
      understanding between you and Montgomery Securities concerning the subject
      matter of this  Agreement.  You may not assign your rights or  obligations
      hereunder  without first obtaining the prior written consent of Montgomery
      Securities.  Notice  or  other  communications,  including  margin  calls,
      delivered  or mailed to the address  given below shall,  until  Montgomery
      Securities  has  received  notice in writing of a  different  address,  be
      deemed to have been personally delivered to you.

14.  ARBITRATION.

            o     ARBITRATION IS FINAL AND BINDING ON THE PARTIES.

            o     THE PARTIES ARE WAIVING THEIR RIGHT TO SEEK REMEDIES IN COURT,
                  INCLUDING THE RIGHT TO JURY TRIAL.

            o     PRE-ARBITRATION  DISCOVERY IS GENERALLY  MORE LIMITED THAN AND
                  DIFFERENT FROM COURT PROCEEDINGS.

            o     THE  ARBITRATORS'  AWARD IS NOT  REQUIRED  TO INCLUDE  FACTUAL
                  FINDINGS OR LEGAL REASONING AND ANY PARTY'S RIGHT TO APPEAL OR
                  TO SEEK MODIFICATION OF RULINGS BY THE ARBITRATORS IS STRICTLY
                  LIMITED.

            o     THE PANEL OF ARBITRATORS WILL TYPICALLY  INCLUDE A MINORITY OF
                  ARBITRATORS  WHO WERE OR ARE  AFFILIATED  WITH THE  SECURITIES
                  INDUSTRY.

      YOU  AGREE,  AND BY  CARRYING  AN  ACCOUNT  FOR YOU,  WE  AGREE,  THAT ALL
      CONTROVERSIES WHICH MAY ARISE BETWEEN US CONCERNING ANY TRANSACTION OR THE
      CONSTRUCTION, PERFORMANCE OR BREACH OF THIS OR ANY OTHER AGREEMENT BETWEEN
      US,  WHETHER  ENTERED INTO PRIOR,  ON, OR  SUBSEQUENT  TO THE DATE HEREOF,
      SHALL BE DETERMINED BY ARBITRATION.  ANY ARBITRATION  UNDER THIS AGREEMENT
      SHALL BE CONDUCTED ONLY IN THE FORUMS PROVIDED BY THE NATIONAL ASSOCIATION
      OF  SECURITIES  DEALERS,  INC. OR THE BOARD OF  GOVERNORS  OF THE NEW YORK
      STOCK  EXCHANGE,  INC., AS YOU MAY ELECT. IF YOU DO NOT MAKE SUCH ELECTION
      BY REGISTERED  MAIL  ADDRESSED TO MONTGOMERY  SECURITIES,  600  MONTGOMERY
      STREET, SAN FRANCISCO, CA 94111, ATTENTION: LEGAL DEPARTMENT, AND RECEIVED
      WITHIN  FIVE DAYS  AFTER  DEMAND BY US THAT YOU MAKE SUCH  ELECTION,  THEN
      MONTGOMERY   SECURITIES  MAY  MAKE  SUCH   ELECTION.   THE  AWARD  OF  THE
      ARBITRATORS, OR OF THE MAJORITY OF THEM, SHALL BE FINAL, AND JUDGMENT UPON
      ANY AWARD RENDERED BY THE  ARBITRATORS  MAY BE ENTERED IN ANY COURT HAVlNG
      JURISDICTION THEREOF.

      No person shall bring a putative or certified class action to arbitration,
      nor seek to enforce  any  pre-dispute  arbitration  agreement  against any
      person  who has  initiated  in court a putative  class  action or who is a
      member of a putative class who has not opted out of the class with respect
      to any claims  encompassed  by the putative  class action  until:  (i) the
      class certification is denied; (ii) the class is decertified; or (iii) the
      customer  is excluded  from the class by the court.  Such  forbearance  to
      enforce an  agreement to  arbitrate  shall not  constitute a waiver of any
      rights under this agreement except to the extent stated herein.


                               Page 8 of 14 Pages





15.   NEW  YORK LAW TO  GOVERN.  This  Agreement  and its  enforcement  shall be
      governed  by the  laws of the  State of New York  (without  regard  to any
      principles of conflicts of law) and its  provisions  shall be  continuous;
      shall cover  individually and collectively all accounts which you may open
      or  reopen  with  us,  and  shall  inure  to the  benefit  of our  present
      organization,  and any successor organization,  irrespective of any change
      or changes at any time in the personnel thereof, for any cause whatsoever,
      and  of  the  assigns  of  our  present   organization  or  any  successor
      organization,   and  shall  be  binding  upon  you,  and/or  your  estate,
      executors, administrators, heirs and assigns.

16.   PARTIAL  UNENFORCEABILITY.  If any  provision  herein is or should  become
      inconsistent  with any present or future law,  rule or  regulation  of any
      sovereign  government or a regulatory  body having  jurisdiction  over the
      subject  matter  of  this  Agreement  or is held  to be  invalid,  void or
      unenforceable by reason of any law, rule, administrative order or judicial
      decision,  such  provision  shall be deemed to be rescinded or modified in
      accordance with any such law, rule, regulation,  order or decision. In all
      other respects, this Agreement shall continue and remain in full force and
      effect.

17.   LIMIT ORDERS. Montgomery Securities reserves the right to not accept from
      customers limit orders in NASDAQ or  over-the-counter  securities in which
      it acts as a market maker.

18.   MARGIN IN MARGIN ACCOUNTS (NOT APPLICABLE TO CASH ACCOUNTS). You hereby
      agree to  maintain  such  margin  in your  margin  account  as  Montgomery
      Securities may in its discretion require and you agree to pay forthwith on
      demand  any  debit  balance  owing  with  respect  to any of  your  margin
      accounts,  and if not paid this  shall be a breach of this  Agreement  and
      Montgomery  Securities may take such action as it considers  necessary for
      its protection in accordance  with this  Agreement.  You understand  that,
      even if Montgomery Securities has a policy of giving customers notice of a
      margin  deficiency,  Montgomery  Securities  is not  obligated  to request
      additional  margin  from  you,  and  there  may  be  circumstances   where
      Montgomery  Securities will liquidate  securities and/or other property in
      your account  without notice to you. You will be charged  interest on your
      debit balance which if not paid at the close of an interest period will be
      added to the opening balance for the next interest period.  Please consult
      the attached disclosure statement for an outline of Montgomery Securities'
      interest policies.

19.   CUSTOMER'S CONSENT TO LOAN OR PLEDGE OF SECURITIES AND OTHER PROPERTY (NOT
      APPLICABLE TO CASH ACCOUNTS).  You hereby authorize Montgomery  Securities
      to lend either to itself or to others any  securities  and other  property
      held by Montgomery Securities in your margin account and to carry all such
      property in its general loans and such property may be pledged, repledged,
      hypothecated or  rehypothecated,  without notice to you, either separately
      or in common with other such  property  for any amounts due to  Montgomery
      Securities  thereon or for a greater sum, and Montgomery  Securities shall
      have no  obligation  to retain a like  amount of similar  property  in its
      possession and control.

      BY SIGNING THIS  AGREEMENT  YOU  ACKNOWLEDGE  THAT THE  SECURITIES IN YOUR
      MARGIN  ACCOUNT MAY BE LOANED TO  MONTGOMERY  SECURITIES  OR LOANED OUT TO
      OTHERS AND THAT YOU HAVE RECEIVED AND REVIEWED A COPY OF THIS AGREEMENT.

      THIS AGREEMENT  CONTAINS A PRE-DISPUTE  ARBITRATION CLAUSE AT PAGES 2-3 AT
      PARAGRAPH 14.

      IF JOINT  ACCOUNT  BOTH PARTIES  MUST SIGN.  Persons  signing on behalf of
others please indicate title or capacity in which you have signed.



                               Page 9 of 14 Pages



               Harold Waitz
- ------------------------------------------------
            (Typed or Printed Name)

               /s/: Harold Waitz
- ------------------------------------------------
                  (Signature)


- ------------------------------------------------
                  (Signature)

c/o BioTime, Inc., 935 Pardee Street
- ------------------------------------------------
               (Mailing Address)

     Berkeley,           CA             94710
- ------------------------------------------------
        (City)         (State)           (Zip)

                        9/12/97
- ------------------------------------------------
                       (Date)


Acct.     XXX-XXXXX-XXX
No.:____________________________________________


                               Page 10 of 14 Pages





                         ADDENDUM TO CUSTOMER AGREEMENT



      Hypothecation of Customer Securities. Notwithstanding any provision of the
Customer Agreement to the contrary, Montgomery Securities shall not lend, pledge
or hypothecate any securities owned by Customer  (whether or not such securities
are held by Montgomery  Securities as Collateral for Customer's  Obligations) to
facilitate any short sale or otherwise;  provided, that this provision shall not
prevent the sale of Collateral pursuant to Section 4.

      Death or  Incompetency  of Customer.  Montgomery  Securities will not take
action  pursuant  to Section 4 solely  because of  Customer's  death or adjudged
incompetency if either (a) within 30 days after the date of Customer's  death or
declaration  of  incompetency  and  an  administrator,   executor,  conservator,
guardian or other  personal  representative  has  authority  to make  investment
decisions with respect to Customer's  account, or (b) with respect to Customer's
incompetency,   Customer  has  executed  a  power  of  attorney  designating  an
attorney-in-fact  who shall  have the power to make  investment  decisions  with
respect to Customer's account.



/s/: Harold Waitz                               /s/: Wilson T. Hileman
- ----------------------------                  ----------------------------
Customer Signature                              For Montgomery Securities

Harold Waitz                               Wilson T. Hileman, Managing Director
- ----------------------------               ------------------------------------
Print Name                                           Print Name and Title

            XXX-XXXXX-XXX
Account No._________________




                               Page 11 of 14 Pages





                                                                     Exhibit (b)
 
                Representation letter FOR AFFILIATES of a Company
                  whose Stock is used as collateral for Margin




      Montgomery Securities
      600 Montgomery Street
      San Francisco, CA 94111.

         Attn:    Margin Department

         Gentlemen:

                  Reference  is made to the Customer  Agreement I executed  with
         you, pursuant to which you opened and maintain account number XXX-XXXXX
         for me, and which  agreement  governs the extension and  maintenance of
         margin credit with respect to such account.

                  I am an  affiliate  (as  defined in Rule 144 (a) (1) under the
         Securities Act of 1933 (the "Act") of Biotime, Inc. (the "Company").  I
         wish to obtain  margin  credit on not more  than  90,000  shares of the
         common stock (the  "Securities")  of the Company.  I understand that in
         order for you to extend margin credit to me which is  collateralized by
         the  Securities,  you must be able to sell the  Securities  pursuant to
         Rule  144  of  the  Act  ("Rule  14+"),  which  requires  that  certain
         conditions  must be met.  Accordingly,  I hereby  represent  to you and
         covenant with you as follows:

         1.   I acquired  and fully paid for the  Securities  on January  18,
              1991.  The  Securities  are  "restricted  securities"  within  the
              meaning of Rule 144, and bear a legend describing  restrictions on
              the transfer of the Securities.

         2.   In the preceding three months, I, together with all persons who
              are  considered  the same "person" as me under Rule  l44(a)(2) and
              all persons whose sales must be  aggregated  with mine pursuant to
              Rule 144(e)(3), have sold 0 shares of common stock of the Company.
              - --------------------------------------

         3.   The Securities, together with all shares of capital stock of the
              Company held by persons whose sales would be aggregated with sales
              by me  pursuant  to Rule 1  4+(e)(3),  constitute  less  -than the
              greater  of (i) 1% of the  shares of common  stock of the  Company
              currently  outstanding or (ii) the average weekly  reported volume
              of  trading  in the Common  Stock of the  Company on all  national
              securities  exchanges,  through the Nasdaq Stock Market, Inc., and
              /or through the consolidated

                                     Page 12 of 14 Pages





              transaction reporting system. I agree that for the duration of the
              period for which my margin loan from Montgomery is collateralized,
              in whole or in part,  by the  Securities,  I will not transfer any
              shares of capital  stock of the Company to any person  whose sales
              would be aggregated with sales by me pursuant to Rule l44(e)(3).

In  addition,  I have held 26,690  securities  of the Company for a period of at
least two years  from the date  hereof  (the  "Additional  Securities").  I also
p1edge the Additional Securities as collateral in order for you to extend margin
credit to me. I understand that you may sell the Additional  Securities  without
regard to the  volume  'imitation  under Rule 144 if you  institute  foreclosure
proceedings against my account.

         4.   I agree that for the duration of the period for which my margin
              loan from Montgomery Securities is collateralized,  in whole or in
              part,  by the  Securities,  I will not sell,  and I will cause all
              persons  who are  considered  the same  "person"  as me under Rule
              l44(a)(2) not to sell, any shares of common stock of the Company.

         5.   I will not use any margin credit to purchase  securities of any
              other company of which lam an affiliate (as defined in Rule 144(a)
              (1)).

         6.   I have no outstanding borrowing  collateralized by any shares of
              capital  stock of the Company and I will not incur such  borrowing
              from any other  person for the duration of the period for which my
              margin loan from Montgomery Securities is collateralized, in whole
              or in part, by the Securities.

         7.   I have  delivered  to you an  executed  Form  144,  a  Seller's
              Representation  Letter under Rule 144 and such other  documents as
              you have requested to enable you to sell the Securities under Rule
              144 at any time you may consider it necessary for your protection.
              The information  contained in these documents is true and correct.
              You may rely on the continued  accuracy and  completeness  of such
              information  unless and until I have informed you m writing of any
              changes to such  information  and have provided you with corrected
              versions  of such  documents I will not take any action or omit to
              take any action that would prevent you from selling the Securities
              at any time pursuant to Rule 144.

         8.  I will notify you  immediately  of any  occurrence  which would
              render any of the foregoing representations inaccurate.

         9.   I am  familiar  with  the  provisions  of  Section  16 of  the
              Securities   Exchange  Act  of  1934  and  the  rules  promulgated
              thereunder.  I understand the possible  consequences  to me if you
              sell the  Securities  at a time when such sale  would  deem 'me to
              have received  "short-swing"  profits,  which  consequences  could
              include the payment to the Company by me of all such profits.

                               Page 13 of 14 Pages




The Company, its transfer agent and their agents and representatives may rely on
this letter. I will indemnify you and hold you harmless from and against any and
all loss, damage, claim,  liability and expense arising out of or resulting from
the breach of any representation or covenant herein.

Very truly yours,


Harold Waitz

                               Page 14 of 14 Pages