<PAGE>
                                                                    EXHIBIT 4.4
                              AXON INSTRUMENTS, INC

                                ARBN 090 106 844
      (incorporated in California, United States of America, with liability
                             of its members limited)

                                   PROSPECTUS

         in relation to an offer of Entitlement Options to shareholders
                        of Circadian Technologies Limited

           This is an important document. You may wish to consult your
        professional advisor about its contents. You should read the full
               text of this Prospectus and the incorporated parts
                of Axon's First Prospectus dated 28 January 2000
              before deciding whether to take up your entitlements.

<PAGE>

CORPORATE DIRECTORY

DIRECTORS

Alan Stockdale (Chairman)
Alan Finkel (Chief Executive Officer)
Geoffrey Powell (Executive President)
Henry Lester (Non-Executive Director)
Stanley Crooke (Non-Executive Director)

INDEPENDENT ACCOUNTANTS
Ernst & Young (Australia)
120 Collins Street
Melbourne, Victoria 3000
Telephone (03) 9288 8000

AUDITORS
Ernst & Young (US)
1451 California Avenue
Palo Alto, CA 94304, USA
Telephone 0011 1 650 496 1600

AUSTRALIAN LAWYERS TO THE ISSUE

Minter Ellison
Level 23
Rialto Towers
525 Collins Street
Melbourne, Victoria 3000
Telephone (03) 9229 2000

SHARE AND OPTION REGISTRY

Computershare Registry Services Pty Ltd
Level 12
565 Bourke Street
Melbourne, Victoria 3000
Telephone (03) 9611 5711

COMPANY SECRETARIES

Geoffrey Powell (USA)
David Kenley (Australia)

REGISTERED OFFICE
1101 Chess Drive
Foster City, CA 94404, USA
Telephone 0011 1 650 571 9400
Email InvestorInfo@axon.com
www.axon.com

REGISTERED OFFICE IN AUSTRALIA
6 Wallace Avenue
Toorak, Victoria 3142, Australia
Telephone (03) 9826 0399
Email InvestorInfo@axon.com

   THE ENTITLEMENT OPTIONS OFFERED UNDER THIS PROSPECTUS AND ANY SHARES TO BE
  ISSUED ON THEIR EXERCISE HAVE NOT BEEN, AND WILL NOT BE, REGISTERED UNDER THE
       UNITED STATES SECURITIES ACT OF 1933 (THE 'US SECURITIES ACT') AND,
     MAY NOT BE OFFERED, SOLD OR DELIVERED WITHIN THE UNITED STATES OR TO OR
       FOR THE ACCOUNT OR BENEFIT OF U.S. PERSONS OTHER THAN DISTRIBUTORS
    UNLESS THE ENTITLMENT OPTIONS OR SUCH SHARES ARE REGISTERED UNDER THE US
      SECURITIES ACT, OR AN EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF
      THE US SECURITIES ACT IS AVAILABLE. IN ADDITION, HEDGING TRANSACTIONS
   WITH REGARD TO THE ENTITLEMENT OPTIONS AND ANY SHARES TO BE ISSUED ON THEIR
    EXERCISE MAY NOT BE CONDUCTED UNLESS IN ACCORDANCE WITH THE US SECURITIES
    ACT. SEE SECTION 1.9 "SEC REQUIREMENTS" AND SECTION 3.3 "RIGHTS ATTACHING
                            TO ENTITLEMENT OPTIONS".

<PAGE>

MESSAGE FROM THE CHIEF EXECUTIVE OFFICER

11 April 2000

Dear Circadian Shareholders,

As Chief Executive Officer of Axon Instruments, Inc ('AXON'), I have great
pleasure in presenting this Prospectus.

Axon was formed in the United States in 1984 to develop instruments for use by
neuroscientists studying electrical activity in brain cells. Axon's business is
expanding to include instruments of Genomics and drug discovery.

Shares in Axon commenced official quotation on the Australian Stock Exchange
('ASX') on 3 March 2000 pursuant to an offer made to the public in its
prospectus dated 28 January 2000 ('FIRST PROSPECTUS').

This Prospectus explains how, as a shareholder of Circadian, you are offered
options to take up unissued securities in Axon at 1 cent per option. You should
read this Prospectus carefully, before making a decision to take up the options
in Axon.

The Directors join me in offering you the opportunity to participate directly in
the ownership of Axon and we look forward to welcoming you as an optionholder of
Axon.

Yours faithfully,

/s/ Alan Finkel

Alan Finkel
Chief Executive Officer

                                                                               1

<PAGE>

TABLE OF CONTENTS

<TABLE>
<S>                                                                                                          <C>
SECTION 1  - OFFER OF ENTITLEMENT OPTIONS.........................................................            4
           1.1       The Offer....................................................................            4
           1.2       Key Dates....................................................................            4
           1.3       The alternatives available to Circadian Shareholders ........................            4
           1.4       Payment......................................................................            5
           1.5       No Minimum Subscription......................................................            5
           1.6       Underwriting.................................................................            5
           1.7       Circadian Shareholders Resident Outside Australia and New Zealand ...........            6
           1.8       Reference to First Prospectus................................................            7
           1.9       SEC Requirements.............................................................            8

SECTION 2  -  INVESTMENT OVERVIEW.................................................................           11
           2.1       Capital Structure............................................................           11
           2.2       Top Ten Shareholders ........................................................           11
           2.3       Risk Factors.................................................................           11

SECTION 3  -  ADDITIONAL INFORMATION..............................................................           12
           3.1       Directors' Interests ........................................................           12
           3.2       Other interests of Directors.................................................           13
           3.3       Rights Attaching to Entitlement Options......................................           13
           3.4       Interests and Consents of Experts............................................           15
           3.5       Consents to be Named.........................................................           16
           3.6       Costs of the Offer...........................................................           18

SECTION 4  - DEFINED TERMS........................................................................           18

SECTION 5  - AUTHORISATION........................................................................           21
</TABLE>

ENTITLEMENT AND APPLICATION FORM

This Prospectus is dated 11 April 2000 and has an expiry date of 10 April 2001.
No securities will be issued on the basis of this Prospectus after the expiry
date.

A copy of this Prospectus has been lodged with the Australian Securities and
Investments Commission ('ASIC'). ASIC takes no responsibility for the content of
this Prospectus.

Copies of the Prospectus will be available on request to members of the public
who are eligible to purchase Entitlement Options by calling (03) 9826 0399
during the Exposure Period. Copies requested will be sent by way of paper copy
or by facsimile as determined by the Company. The Company will not accept
applications for securities offered under this Prospectus during the Exposure
Period.

REFERENCES TO CIRCADIAN TECHNOLOGIES LIMITED

References in this Prospectus to Circadian Technologies Limited or shareholders
of Circadian are included solely for the purposes of identification of the
persons entitled to participate in the Offer of Entitlement Options under this
Prospectus. Such references do not constitute, and are not to be construed as,
any express or implied endorsement by Circadian of the Offer of Entitlement
Options under this Prospectus. Circadian does not accept responsibility for any
statement in this Prospectus nor does it undertake any liability in respect of
the grant or exercise of any Entitlement Options offered under this Prospectus.

2

<PAGE>

RELATIONSHIP WITH CIRCADIAN TECHNOLOGIES LIMITED

References in this Prospectus to Circadian have been prepared from publicly
available information. Circadian has not been a party to its preparation or
furnished any information to Axon specifically for the purpose of the
preparation of this Prospectus. Circadian has not been involved in the
preparation of this Prospectus.

For information of the interests of the directors of Axon in shares in
Circadian, see section 3.1.

ASX QUOTATION

It is not currently proposed that the Entitlement Options will be quoted on ASX
due to regulatory limitations of the Australian Corporations Law. A secondary
market in the Entitlement Options therefore cannot be assumed.

Shares issued on exercise of the Entitlement Options will rank equally in all
respects with existing shares in Axon.

Axon will apply for quotation of the shares issuable or issued upon exercise of
the Entitlement Options and, provided certain US regulatory requirements are
met, those shares will be eligible to be quoted on ASX in the same manner as
other shares in Axon.

                                                                               3

<PAGE>

SECTION 1 - OFFER OF ENTITLEMENT OPTIONS

1.1      THE OFFER

         This Prospectus provides information on Axon's Offer to Circadian
         shareholders. Shareholders of Circadian (other than shareholders with
         registered addresses outside Australia or New Zealand) have a right to
         take up an equitable right or interest in 1 option for every 2.5 shares
         in Circadian held at 5.00 pm Melbourne time on the Record Date for
         entitlements (namely 20 March 2000) at 1 cent per option (the
         underlying option, 'ENTITLEMENT OPTION'). Each Entitlement Option is
         exercisable at any time on or before 5.00 pm Melbourne legal time on 10
         May 2005. The exercise price for each Entitlement Option (which is
         payable immediately on exercise) is A$0.20. Any fractional entitlement
         will be rounded down to the nearest whole share. Special arrangements
         for shareholders of Circadian with registered addresses outside
         Australia or New Zealand are set out in section 1.7 below.

         The cost of 1 cent per Entitlement Option is payable in full on
         application. Holdings of Circadian shares on different registers (or
         subregisters) will be aggregated for calculating entitlements. Rights
         to Entitlement Options are non-renounceable, so the rights may not be
         sold or otherwise renounced or disposed of.

         The maximum number of Entitlement Options which may be issued under
         this Offer is 12,997,845. Details of how Circadian shareholders can
         take up entitlements to Entitlement Options are set out in section 1.3
         below.

1.2      KEY DATES

         Record Date to determine entitlements of Circadian
         shareholders to Entitlement Options                      20 March 2000

         Entitlement Option acceptances close                     10 May 2000

         Entitlement Option acceptances from member
         organisations close                                      15 May 2000

1.3      THE ALTERNATIVES AVAILABLE TO CIRCADIAN SHAREHOLDERS

         The number of Entitlement Options to which you are entitled
         ('Entitlement') is shown on the accompanying Entitlement and
         Application Form.

         You may:

         -        take up your Entitlement in full;

         -        take up part of your Entitlement and allow the balance to
                  lapse; or

         -        allow your Entitlement to lapse.

         Rights to Entitlement Options are non-renounceable, so the rights may
         not be sold or otherwise renounced or disposed of.

4

<PAGE>

         IF YOU WISH TO TAKE UP ALL OF YOUR ENTITLEMENT

         Complete the accompanying Entitlement and Acceptance Form in accordance
         with the instructions set out in the Form. Forward your completed form,
         together with your cheque in payment of the total amount payable to
         Computershare Registry Services Pty Ltd at Level 12, 565 Bourke Street,
         Melbourne, Victoria 3000. Duly completed applications must be received
         by Computershare Registry Services Pty Ltd by no later than 5.00 pm
         Australian Eastern Standard Time on 10 May 2000.

         IF YOU WISH TO TAKE UP PART OF YOUR ENTITLEMENT AND ALLOW THE BALANCE
         TO LAPSE

         Complete the accompanying Entitlement and Application Form in respect
         of Entitlement Options you wish to take up and forward the Form,
         together with your cheque in payment of the requisite amount (being the
         number of Entitlement Options you wish to take up multiplied by 1 cent)
         to Computershare Registry Services Pty Ltd at Level 12, 565 Bourke
         Street, Melbourne, Victoria 3000. Duly completed applications must be
         received by Computershare Registry Services Pty Ltd by no later than
         5.00 pm Australian Eastern Standard Time on 10 May 2000.

         IF YOU WISH TO ALLOW YOUR ENTITLEMENT TO LAPSE

         If you wish to allow your Entitlement to lapse, you need not do
         anything. If your duly completed Entitlement and Acceptance Form is not
         received by Computershare Registry Services Pty Ltd by no later than
         5.00 pm Australian Eastern Standard Time on 10 May 2000, your
         Entitlement will automatically lapse, and you will receive no benefit.

1.4      PAYMENT

         Acceptance for Entitlement Options must be accompanied by payment in
         full of 1 cent per Entitlement Option accepted. Payments will only be
         accepted in Australian currency and by a cheque drawn on and payable at
         any Australian bank that is honoured on presentation.

         Cheques should be made payable to 'Axon Instruments, Inc - Float
         Account' and crossed 'not negotiable'. You should not forward cash.
         Receipts for payments will not be forwarded to applicants.

         By accepting the offer (wholly or in part) you will agree to be bound
         by the terms and conditions of the Entitlement Options granted to you
         as set out in section 3.3.

1.5      NO MINIMUM SUBSCRIPTION

         There is no minimum subscription.

1.6      UNDERWRITING

         The Offer is not underwritten.

                                                                               5

<PAGE>

   THE ENTITLEMENT OPTIONS OFFERED UNDER THIS PROSPECTUS AND ANY SHARES TO BE
    ISSUED ON THEIR EXERCISE HAVE NOT BEEN, AND WILL NOT BE, REGISTERED UNDER
    THE UNITED STATES SECURITIES ACT OF 1933 (THE 'U.S. SECURITIES ACT') AND,
   MAY NOT BE OFFERED, SOLD OR DELIVERED WITHIN THE UNITED STATES OR TO OR FOR
    THE ACCOUNT OR BENEFIT OF U.S. PERSONS OTHER THAN DISTRIBUTORS UNLESS THE
        ENTITLEMENT OPTIONS OR SUCH SHARES ARE REGISTERED UNDER THE U.S.
 SECURITIES ACT, OR AN EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE U.S.
   SECURITIES ACT IS AVAILABLE. IN ADDITION, HEDGING TRANSACTIONS WITH REGARD
         TO THE ENTITLEMENT OPTIONS AND ANY SHARES TO BE ISSUED ON THEIR
         EXERCISE MAY NOT BE CONDUCTED UNLESS IN ACCORDANCE WITH THE US
             SECURITIES ACT. SEE SECTION 1.9 "SEC REQUIREMENTS" AND
             SECTION 3.3 "RIGHTS ATTACHING TO ENTITLEMENT OPTIONS".

1.7      CIRCADIAN SHAREHOLDERS RESIDENT OUTSIDE AUSTRALIA AND NEW ZEALAND

         Circadian shareholders resident outside Australia and New Zealand and
         shareholders who are nominees of persons resident outside Australia and
         New Zealand should consult their professional advisers as to whether
         any governmental or other consents are required, or whether formalities
         need to be observed, to enable them to accept their entitlements.

         This Prospectus does not constitute an offer in any place in which, or
         to any person to whom, it would not be lawful to make such an offer.

         Neither the rights to the Entitlement Options nor the Entitlement
         Options themselves nor the Securities in Axon underlying the
         Entitlement Options will have been registered under the securities laws
         of any country other than Australia and New Zealand.

         Accordingly, this Prospectus has not been sent to holders of shares
         registered with addresses in any country outside Australia or New
         Zealand, or any of their respective territories or possessions or other
         areas subject to such country's control.

         Axon will send to each Circadian shareholder with a registered address
         outside Australia or New Zealand details of the Offer of Entitlement
         Options under this Prospectus and advice that Axon will not offer
         Entitlement Options to that holder. In particular, a Circadian
         Shareholder that is a U.S. Person is excluded from participation in the
         offer on terms outlined in sections 1.9 and 3.3.

         Instead, the Entitlement Options that would otherwise have been offered
         to that holder will, subject to the following paragraph, be granted to
         a nominee appointed by the directors of Circadian, and the Entitlement
         Options sold (subject to compliance with Regulation S under the US
         Securities Act) if there is a viable market in those options and a
         premium over the expenses of sale can be obtained. Any such sale will
         be at such prices and otherwise in such manner as the nominee may in
         its sole discretion determine. The ability to sell the Entitlement
         Options granted to the nominee and the price obtained for them are
         dependent on market conditions. None of Axon, Circadian or the nominee
         will be subject to any liability for failure to sell Entitlement
         Options at any particular price. The net proceeds of the sale (if any)
         after deducting all costs involved in the sale and the subsequent
         distribution of cash, will be distributed pro rata to each of the
         Circadian shareholders for whose benefit the Entitlement Options have
         been sold. The net proceeds of the sale (if any) will be paid in
         Australian currency to the Circadian shareholders concerned.

         If there is not a viable market for Entitlement Options or the nominee
         believes a

6

<PAGE>

         premium over the expenses of sale cannot be obtained, the nominee will
         not be granted the Entitlement Options, and no proceeds of sale or any
         other monies will be paid to the Circadian shareholders concerned.

1.8      REFERENCE TO FIRST PROSPECTUS

         Reference is made to Axon's prospectus dated and lodged with ASIC on 28
         January 2000 ('FIRST PROSPECTUS').

         INFORMATION CONTAINED IN THE FIRST PROSPECTUS

         Information in the First Prospectus that is in the opinion of Directors
         primarily of interest to professional analysts or advisers or investors
         with similar specialist information needs is contained in the following
         section:

         Section 8 - Independent Accountant's Report contains Ernst & Young's
         Independent Accountant's Report covering the 6 month period ended 30
         June 1999 and the financial years ended 31 December 1998 and 1997.

         Section 9 - Valuation by Independent Expert contains Acuity Technology
         Management Pty Ltd's report on the valuation of Axon.

         Information in the First Prospectus that is in the opinion of Directors
         of primary interest to Circadian shareholders in deciding whether to
         take up their entitlement to Entitlement Options is contained in the
         following sections:

         Section 3 (other than 3.3) - Investment Overview - contains information
         on company background, purpose of the offer, capital structure, risk
         factors, business objectives and working capital.

         Section 4 - Business of Axon - contains information on Axon's markets
         and products, corporate goals, intellectual property and scientific and
         technical advisors.

         Section 5 - The Directors - contains information on the Directors of
         Axon.

         Section 10 - Risk Factors - contains information on the specific and
         general risks associated with an investment in Axon.

         Section 11 (not including 11.7) - Additional Information - contains
         information on: incorporation; company tax status; audit committee;
         corporate governance; legal proceedings; and rights attaching to
         Securities, Underlying Shares, Entitlement Options, Individual Options
         and Original Options.

         RIGHT TO OBTAIN COPY

         A copy of the First Prospectus was forwarded to all Circadian
         shareholders on the register as at 8 February 2000.

         Circadian shareholders may obtain a further copy of the First
         Prospectus free of charge, during the application period of this Offer.
         Requests for copies of the First Prospectus can be made to 6 Wallace
         Avenue, Toorak, Victoria, 3142, Australia, telephone (03) 9826 0399.

                                                                               7

<PAGE>

         Circadian shareholders should read the full text of this Prospectus and
         the referred parts of the First Prospectus before deciding whether to
         take up their Entitlements.

         The information set out in this section is not intended to be
         comprehensive and should be read in conjunction with the full text of
         this Prospectus including the referred parts of the First Prospectus.

1.9      SEC REQUIREMENTS

         The Entitlement Options and any Shares to be issued on their exercise
         have not been and will not be registered under the United States
         Securities Act of 1933 (the 'U.S. SECURITIES ACT') and may not be
         offered or sold in the United States or to, or for the account or
         benefit of, U.S. Persons other than distributors as part of their
         distribution at any time or until the date that is one year after the
         completion of the distribution of the Entitlement Options. Following
         such one-year restricted period, the Entitlement Options and any shares
         issuable upon the exercise of Entitlement Options may be sold in the
         United States or to, or for the account of benefit of, U.S. Persons
         only in transactions that are exempt from the registration requirements
         of the U.S. Securities Act. In addition, hedging transactions with
         regard to the Entitlement Options and any Shares to be issued on their
         exercise may not be conducted unless in accordance with the U.S.
         Securities Act. Terms used in this paragraph have the meaning given to
         them by Regulation S under the U.S. Securities Act.

         Until the completion of the one-year restriction period, each
         subscriber/purchaser of Entitlement Options will be deemed to have
         represented and agreed as follows:

         (1)      It is not a U.S. Person and is not acquiring the Entitlement
                  Options for the account or benefit of a U.S. Person, or is a
                  U.S. Person who acquired the Entitlement Options in a
                  transaction that did not require registration under the U.S.
                  Securities Act.

         (2)      It understands that the Entitlement Options have not been
                  registered under the U.S. Securities Act and that, if in the
                  future it decides to offer, resell, pledge or otherwise
                  transfer such Entitlement Options, the Entitlement Options may
                  be offered, sold, pledged or otherwise transferred only (a) in
                  an offshore transaction in accordance with Rule 903 or 904 of
                  Regulation S under the U.S. Securities Act, or (b) pursuant to
                  an exemption from registration under the U.S. Securities Act,
                  in each case in accordance with any applicable securities laws
                  of any state of the United States.

         (3)      It agrees not to engage in hedging transactions with regard to
                  the Entitlement Options unless in compliance with the U.S.
                  Securities Act.

         (4)      It understands that the certificates representing Entitlement
                  Options will bear a legend to the following effect unless Axon
                  determines otherwise consistent with applicable law:

                  "THE ENTITLEMENT OPTIONS OF AXON INSTRUMENTS INC AND ANY
                  SHARES TO BE ISSUED ON THEIR EXERCISE HAVE NOT BEEN AND WILL
                  NOT BE REGISTERED UNDER THE UNITED STATES SECURITIES ACT OF
                  1933, AS AMENDED (THE 'U.S. SECURITIES ACT'). THE ENTITLEMENT
                  OPTIONS AND ANY SHARES ISSUED ON THEIR EXERCISE MAY NOT BE
                  OFFERED, SOLD, PLEDGED OR

8

<PAGE>

                  OTHERWISE TRANSFERRED EXCEPT (A) IN AN OFFSHORE TRANSACTION IN
                  ACCORDANCE WITH RULE 903 OR 904 OF REGULATION S UNDER THE U.S.
                  SECURITIES ACT OR (B) PURSUANT TO AN EXEMPTION FROM
                  REGISTRATION UNDER THE U.S. SECURITIES ACT, IN EACH CASE IN
                  ACCORDANCE WITH ANY APPLICABLE SECURITIES LAWS OF ANY STATE OF
                  THE UNITED STATES. IN ADDITION, HEDGING TRANSACTIONS WITH
                  REGARD TO THE ENTITLEMENT OPTIONS AND ANY SHARES ISSUED ON
                  THEIR EXERCISE MAY NOT BE CONDUCTED UNLESS IN COMPLIANCE WITH
                  THE U.S. SECURITIES ACT."

         SHARES ISSUABLE UPON EXERCISE OF ENTITLEMENT OPTIONS

         Until the completion of the one-year restriction period, each person
         who exercises Entitlement Options and each person who acquires shares
         in Axon that were issued upon exercise of Entitlement Options will be
         deemed to have represented and agreed as follows:

         (1)      It is not a U.S. Person and is not exercising the Entitlement
                  Options or acquiring such shares for the account or benefit of
                  a U.S. Person, or is a U.S. Person who is exercising the
                  Entitlement Options or acquiring such shares in a transaction
                  that did not require registration under the U.S. Securities
                  Act.

         (2)      It understands that the shares issuable or issued, as the case
                  may be, upon exercise of the Entitlement Options will not be
                  and have not been registered under the US Securities Act and
                  that, if in the future it decides to offer, resell, pledge or
                  otherwise transfer such shares, the shares may be offered,
                  sold, pledged or otherwise transferred only (a) in an offshore
                  transaction in accordance with Rule 903 or 904 of Regulation S
                  under the U.S. Securities Act, or (b) pursuant to an exemption
                  from registration under the U.S. Securities Act, in each case
                  in accordance with any applicable securities laws of any state
                  of the United States.

         (3)      It agrees not to engage in hedging transactions with regard to
                  the shares issuable or issued, as the case may be, upon
                  exercise of the Entitlement Options unless in compliance with
                  the U.S. Securities Act.

         (4)      It understands that the certificates representing the shares
                  issuable or issued, as the case may be, upon exercise of the
                  Entitlement Options will bear a legend to the following effect
                  unless Axon determines otherwise consistent with applicable
                  law:

                  "THE SHARES OF AXON INSTRUMENTS INC REPRESENTED BY THIS
                  CERTIFICATE HAVE NOT BEEN AND WILL NOT BE REGISTERED UNDER THE
                  UNITED STATES SECURITIES ACT OF 1933, AS AMENDED (THE "U.S.
                  SECURITIES ACT"). THE SHARES MAY NOT BE OFFERED, SOLD, PLEDGED
                  OR OTHERWISE TRANSFERRED EXCEPT (A) IN AN OFFSHORE TRANSACTION
                  IN ACCORDANCE WITH RULE 903 OR 904 OF REGULATION S UNDER THE
                  U.S. SECURITIES ACT OR (B) PURSUANT TO AN EXEMPTION FROM
                  REGISTRATION UNDER THE U.S. SECURITIES ACT, IN EACH CASE IN
                  ACCORDANCE WITH ANY APPLICABLE SECURITIES LAWS OF ANY STATE OF
                  THE UNITED STATES. IN ADDITION HEDGING

                                                                               9

<PAGE>

                  TRANSACTION WITH REGARD TO THE SHARES MAY NOT BE CONDUCTED
                  UNLESS IN COMPLIANCE WITH THE U.S. SECURITIES ACT."

         Axon will apply for quotation of the shares issuable or issued upon
         exercise of the Entitlement Options and, provided certain US regulatory
         requirements are met, those shares will be eligible to be quoted on ASX
         in the same manner as other shares in Axon.

10

<PAGE>

SECTION 2 - INVESTMENT OVERVIEW

2.1      CAPITAL STRUCTURE

         The capital structure of Axon before and following the close of this
         Offer is and will be as follows:

<TABLE>
<CAPTION>
                                                                                            Number
<S>                                                                                      <C>
Issued ordinary Shares prior to this Offer                                               400,093,600

Original Options issued and unexercised prior to this Offer (see section                  56,574,067
11.12 of the First Prospectus)

Individual Options offered under the First Prospectus (see section 11.11 of                4,100,000
the First Prospectus)

Entitlement Options offered to Circadian shareholders (see section 1 of this              12,997,845
Prospectus)

Total issued ordinary Shares (assuming all Original Options and Entitlement              473,765,511
Options are exercised).
</TABLE>

2.2      TOP TEN SHAREHOLDERS

         The top ten Shareholders and their percentage Shareholding of Axon at 3
         April 2000 were as follows:

<TABLE>
<CAPTION>
                                                                            PERCENTAGE HOLDING
            SHAREHOLDER                                                             %
-----------------------------------                                         ------------------
<S>                                                                         <C>
Alan Finkel                                                                       24.58
Elizabeth Finkel                                                                  24.58
Precision Patchclamps (Int) Pty Ltd                                               17.70
Geoffrey Powell                                                                    8.34
Cashtree Pty Ltd                                                                   4.74
Hanson Developments Pty Ltd                                                        2.96
Henry Lester                                                                       0.65
ANZ Nominees Limited                                                               0.33
Yuri Osupchuk                                                                      0.33
David Wellis                                                                       0.30
</TABLE>

2.3      RISK FACTORS

         Circadian shareholders should be aware that subscribing for Entitlement
         Options involves a number of risks. These are set out in detail in
         sections 3.4 and 10 of the First Prospectus. Circadian shareholders are
         urged to consider these risk factors carefully before deciding whether
         to subscribe for the Entitlement Options.

                                                                              11

<PAGE>

SECTION 3 - ADDITIONAL INFORMATION

3.1      DIRECTORS' INTERESTS

         This Prospectus sets out the nature and extent of interests (if any)
         that each director (and proposed director) holds, or held at any time
         in the last 2 years, in: the formation or promotion of Axon; property
         acquired or proposed to be acquired by Axon in connection with its
         formation or promotion or the Offer; or, the Offer. This Prospectus
         also sets out the amount that anyone has paid or agreed to pay, or the
         nature of any benefit anyone has given or agreed to give: to a
         director, or proposed director, to induce them to become, or to qualify
         as, a director of Axon; and, for services provided by a director in
         connection with the formation and promotion of Axon or the Offer.

         INTEREST IN CIRCADIAN TECHNOLOGIES LIMITED

         Alan Finkel and his wife, Elizabeth Finkel, are shareholders of
         Circadian holding 285,000 and 385,000 shares respectively.

         SHAREHOLDING QUALIFICATIONS

         The Directors are not required to hold any Shares in Axon under the
         Constitution of Axon.

         REMUNERATION OF DIRECTORS

         The Constitution of Axon provides that the non-executive Directors may
         collectively be paid as remuneration for their services a fixed sum not
         exceeding the aggregate maximum sum from time to time determined by
         Axon in general meeting (currently US$200,000).

         For the current financial year ending 30 June 2000, it is expected that
         the non-executive directors' fees will collectively not exceed
         A$150,000 per annum.

         A Director may be paid fees or other amounts as the Directors determine
         where a Director performs special duties or otherwise performs services
         outside the scope of the ordinary duties of a director. A Director may
         also be reimbursed for out of pocket expenses incurred as a result of
         their directorship or any special duties.

         Each of the Executive Directors, Alan Finkel and Geoffrey Powell, will
         receive salaries from Axon as employees. The employment arrangements
         provide for the payment of salaries and other benefits on commercial
         terms commensurate with the salary packages offered to the executive
         directors of public companies of a similar size and industry grouping
         and are on normal commercial terms. Henry Lester, a non-executive
         director, receives fees for scientific consulting. The fee is paid
         consistent with the amount paid to other scientific consultants for
         similar levels of consulting.

         DIRECTORS' SHAREHOLDINGS

         Set out below are details of the interests of the Directors in the
         securities of Axon immediately prior to lodgement of this Prospectus
         with the ASIC:

12

<PAGE>

<TABLE>
<CAPTION>
   DIRECTOR                                       SHARES                             OPTIONS
---------------                                ------------                        ----------
<S>                                            <C>                                 <C>
Alan Finkel                                     99,997,500*                        10,399,740
Geoffrey Powell                                 33,910,263                          4,622,157
Alan Stockdale                                         Nil                            400,000
Henry Lester                                     2,632,882                          1,100,358
Stanley Crooke                                         Nil                          1,400,000
</TABLE>

         * Alan Finkel's wife Elizabeth Finkel, also holds 99,997,500 Shares.

3.2      OTHER INTERESTS OF DIRECTORS

         Alan Finkel and his wife Elizabeth Finkel are shareholders of Circadian
         :

         (a)      which owns 100% of Precision Patchclamps (Int) Pty Ltd, which
                  owns 66,665,000 Axon Shares; and

         (b)      enables them to participate in the Offer under this
                  Prospectus.

3.3      RIGHTS ATTACHING TO ENTITLEMENT OPTIONS

         The following are the rights attaching to Entitlement Options:

         Each Entitlement Option will entitle the holder of the option
         (`Optionholder') to subscribe for and be issued one fully paid ordinary
         share (`Share') in Axon on the terms and conditions set out below:

         1.       Each Entitlement Option is exercisable at any time on or
                  before 5.00 pm Melbourne legal time on 10 May 2005 ('OPTION
                  PERIOD').

         2.       The Entitlement Options may be exercised wholly or in part by
                  giving notice in writing (`Notice of Exercise') to Axon at any
                  time during the Option Period.

         3.       The exercise price for each Entitlement Option (which is
                  payable immediately on exercise) is A$0.20 (`Exercise Price').

         4.       On receipt by Axon of the Notice of Exercise and payment of
                  the relevant Exercise Price, Axon must, within 14 days, allot
                  to the Option Holder the number of Option Securities in
                  respect of which the Entitlement Option is exercised and
                  despatch the relevant certificate for the Option Securities or
                  other appropriate acknowledgment as soon as reasonably
                  practicable thereafter.

         5.       Each person exercising an Entitlement Option is required to
                  give:

                  (a)      written certification that it is not a U.S. Person
                           and the Entitlement Option is not being exercised on
                           behalf of a U.S. Person; or

                  (b)      a written opinion of counsel to the effect that the
                           Entitlement Options and the shares issued on exercise
                           thereof have been registered under the U.S.
                           Securities Act or are exempt from registration
                           thereunder.

                                                                              13

<PAGE>

         6.       An Entitlement Option may not be exercised within the United
                  States, and shares may not be delivered within the United
                  States upon exercise, unless Axon receives proof satisfactory
                  to it that:

                  (a)      the exercise of the Entitlement Options and the
                           delivery of the shares meets the definition of
                           "offshore transaction" pursuant to Rule 902(h) of
                           Regulation S;

                  (b)      the shares issuable on exercise are registered under
                           the U.S. Securities Act; or

                  (c)      an exemption from such registration is available.

         7.       Subject to paragraph 15, shares allotted on the exercise of
                  any Entitlement Options will rank equally in all respects with
                  the then existing issued Shares in Axon.

         8.       Adjustments to the number of Securities over which Entitlement
                  Options exist and/or the Exercise Price may be made as
                  described in paragraph 10 to take account of changes to the
                  capital structure of Axon by way of pro rata bonus and cash
                  issues. Axon agrees to notify all Option Holders and its Home
                  Branch within one month after the record date for a pro rata
                  bonus or cash issue, of any adjustment to the number of Shares
                  over which the Entitlement Options exist and/or any adjustment
                  to the Exercise Price.

         9.       Subject to paragraphs 8 and 10 Entitlement Options do not
                  confer rights to participate in new issues of securities of
                  Axon.

         10.      The method of adjustment for the purpose of paragraph 8 shall
                  be in accordance with Listing Rule 6.22.2 and 6.22.3 of the
                  Official Listing Rules of the Australian Stock Exchange
                  Limited which provides:

                  (a)      Pro-Rata Cash issues

                           Where a pro-rata issue is made (except a bonus issue)
                           to the holders of underlying securities, the Exercise
                           Price of an option may be reduced according to the
                           following formula:

                           O' =   O - E[P-(S+D)] / N + 1

                           where:

                           O' =   the new exercise price of the option.

                           O =    the old exercise price of the option.

                           E =    the number of underlying securities into which
                                  one option is exercisable.

                           P =    the average market price per security
                                  (weighted by reference to volume) of the
                                  Underlying Share during the 5 trading days

14

<PAGE>

                                  ending on the day before the ex rights date
                                  or ex entitlements date.

                           S =    the subscription price for a security under
                                  the pro rata issue.

                           D =    the dividend due but not yet paid on the
                                  existing underlying securities (except those
                                  to be issued under the pro rata issue).

                           N =    the number of securities with rights or
                                  entitlements that must be held to receive a
                                  right to one new security.

                  (b)      Pro-Rata Bonus Issues

                           If there is a bonus issue to the holders of the
                           underlying securities, on the exercise of any
                           options, the number of securities received will
                           include the number of bonus securities that would
                           have been issued if the options had been exercised
                           prior to the record date for bonus issues. The
                           Exercise Price will not change.

         11.      In the event of any reorganisation (including consolidation,
                  sub-division, reduction or return) of the issued capital of
                  Axon:

                  (a)      the number of Entitlement Options or the Exercise
                           Price or both shall be reorganised (as appropriate)
                           in a manner which will not result in any benefit
                           being conferred on the Option Holders which are not
                           conferred on holders of ordinary securities in Axon;
                           and

                  (b)      Axon may round up the number of Securities to be
                           received on conversion of the Entitlement Options if
                           the rounding up is approved at a meeting of security
                           holders which approves the reorganisation.

         12.      In any reorganisation as referred to in paragraph 11, the
                  treatment of the Entitlement Options by Axon must comply with
                  the ASX Listing Rules applying to a reorganisation of capital
                  at the time of the reorganisation.

         13.      All Entitlement Options will lapse in the event of the
                  liquidation of Axon.

         14.      Entitlement Options are transferable as if they were shares in
                  Axon. However, Axon must refuse to register any transfer of
                  Entitlement Options not made in accordance with the provisions
                  of Regulation S under the U.S. Securities Act, pursuant to
                  registration under the U.S. Securities Act, or pursuant to an
                  available exemption from registration.

         15.      The shares issued on exercise of the Entitlement Options will
                  be eligible to be quoted on ASX, in the same manner as other
                  shares in Axon, provided certain U.S. regulatory requirements
                  are met. There can be no guarantee that any shares issued on
                  exercise of the Entitlement Options will be eligible to be
                  quoted on ASX.

3.4      INTERESTS AND CONSENTS OF EXPERTS

         This Prospectus sets out the nature and extent of interests (if any)
         that each person named in the Prospectus as performing a function in a
         professional advisory or other

                                                                              15

<PAGE>

         capacity in connection with the preparation or distribution of the
         Prospectus holds, or held at any time in the last 2 years, in: the
         formation or promotion of Axon; property acquired or proposed to be
         acquired by Axon in connection with its formation or promotion or the
         Offer; or, the Offer. This Prospectus also sets out the amount that
         anyone has paid or agreed to pay, or the nature of any benefit anyone
         has given or agreed to give to a person named in the Prospectus as
         performing a function in a professional advisory or other capacity in
         connection with the preparation or distribution of the Prospectus; and,
         for services provided in connection with the formation and promotion of
         Axon or the Offer.

         (a)      Ernst & Young (Australia) has prepared the Independent
                  Accountant's Report included in the First Prospectus. Axon has
                  agreed to pay the fees of Ernst & Young for this work on the
                  basis of its usual time related charge out rates. Total
                  estimated fees for work in respect of the First Prospectus and
                  this Prospectus : A$460,000.

                  Ernst & Young (Australia) has given its written consent to the
                  issue of this Prospectus including the incorporation in this
                  Prospectus by reference of the Report appearing in section 8
                  of the First Prospectus in the form and context in which it
                  appears in this Prospectus and has not withdrawn such consent
                  prior to the date of lodgement this Prospectus with the
                  Australian Securities and Investment Commission.

         (b)      Acuity Technology Management Pty Ltd has prepared the
                  valuation of Axon included in the First Prospectus.

                  Acuity Technology Management Pty Ltd has given its written
                  consent to the issue of this Prospectus including the
                  incorporation in this Prospectus by reference of the Valuation
                  by an Independent Expert appearing in section 9 of the First
                  Prospectus in the form and context in which it appears in this
                  Prospectus and has not withdrawn that consent prior to the
                  date of lodgement of this Prospectus with the Australian
                  Securities and Investment Commission. Total fees for work in
                  respect of the First Prospectus and this Prospectus: A$11,500.

         (c)      Minter Ellison has acted as Australian Lawyers to the Issue.
                  Total estimated fees for work in respect of the First
                  Prospectus and this Prospectus: $180,000.

         (d)      Computershare Registry Services Pty Ltd has acted as Share
                  Registry to the Issue. Total estimated fees for this work in
                  respect of the First Prospectus and this Prospectus: $45,000.

3.5      CONSENTS TO BE NAMED

         Each of the following has consented (and has not withdrawn such consent
         prior to the lodgment of this Prospectus with the Australian Securities
         and Investment Commission) to be named in this Prospectus as
         performing, or having performed, in the capacity specified:

         -        Minter Ellison - Australian Lawyers to the Issue

         -        Ernst & Young (Australia) - Independent Accountants

         -        Ernst & Young LLP (US) - Auditors

         -        Computershare Registry Services Pty Ltd - Share Registry

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<PAGE>

         -        Acuity Technology Management Pty Ltd - Independent Valuer

3.6      COSTS OF THE OFFER

         The total estimated costs of the Offer, including legal fees incurred,
         lodgement fees, fees for other advisors, printing expenses and other
         miscellaneous expenses, will be approximately $45,000.

                                                                              17

<PAGE>

SECTION 4 - DEFINED TERMS

The following definitions apply throughout this document unless the context
requires otherwise.

'APPLICANT(S)' means person(s) who submit valid Entitlement and Application
Forms pursuant to this Prospectus.

'ASIC' means the Australian Securities and Investment Commission.

'ASX' means Australian Stock Exchange Limited.

'AXON' means Axon Instruments, Inc ARBN 090 106 844.

'CIRCADIAN' means Circadian Technologies Limited ACN 006 340 567.

'DIRECTORS' means the directors of Axon.

'ENTITLEMENT OPTION' means an equitable right or interest in 1 option, at the
cost of 1 cent, to take up 1 unissued Share at 20 cents at any time on or before
5 years after the date of issue for every 2.5 shares in Circadian held as at the
Record Date.

'ERNST & YOUNG' means Ernst & Young (Australia) and Ernst & Young LLP (US)
unless otherwise stated.

'EXPOSURE PERIOD' means the period between the date of lodgment of this
Prospectus with ASIC and ending 7 days after such lodgment, unless the period is
extended by ASIC, in which event it means the extended period.

'FIRST PROSPECTUS' means Axon's prospectus dated and lodged with ASIC on 28
January 2000.

'INDIVIDUAL OPTIONS' options granted to Geoffrey Powell, Stanley Crooke, Alan
Stockdale, Chris Belyea and David Kenley not pursuant to the stock plan adopted
by Axon Directors and Shareholders in 1987 as described in section 11.11 of the
First Prospectus.

'LISTING RULES' means the official listing rules of the ASX.

'OFFER' means the invitation to the Circadian shareholders to subscribe for a
total of approximately 12,997,845 Entitlement Options.

'ORIGINAL OPTIONS' means option granted to employees, officers and executives of
Axon and associated research staff pursuant to a stock plan adopted by Axon
Directors and shareholders in 1987 as described in section 11.12 of the First
Prospectus.

'PROSPECTUS' means this Prospectus and includes the identified sections of the
First Prospectus.

'RECORD DATE' means 20 March 2000.

'SCH BUSINESS RULES' has the same meaning as in the Corporations Law.

'SHARE(S)' means ordinary shares in the common stock of Axon.

18

<PAGE>

'U.S. PERSON' means:

(a)      any natural person resident in the United States;

(b)      any partnership or corporation organised or incorporated under the laws
         of the United States;

(c)      any estate of which any executor or administrator is a U.S. Person;

(d)      any trust of which any trustee is a U.S. Person;

(e)      any agency or branch of a foreign entity located in the United States;

(f)      any non-discretionary account or similar account (other than an estate
         or trust) held by a dealer or other fiduciary for the benefit or
         account of a U.S. Person;

(g)      any discretionary account or similar account (other than an estate or
         trust) held by a dealer or other fiduciary organised, incorporated or
         (if an individual) resident in the United States; and

(h)      any partnership or corporation if:

         (i)      organised or incorporated under the laws of any foreign
                  jurisdiction; and

         (ii)     formed by a U.S. Person principally for the purpose of
                  investing in securities not registered under the U.S.
                  Securities Act, unless it is organised or incorporated, and
                  owned, by accredited investors (as defined by Rule 501(a)
                  under the U.S. Securities Act) who are not natural persons,
                  estates or trusts.

The following are not U.S. Persons:

(a)      any discretionary account or similar account (other than an estate or
         trust) held for the benefit or account of a non-U.S. Person by a dealer
         or other professional fiduciary organised, incorporated, or (if an
         individual) resident in the United States;

(b)      any estate of which any professional fiduciary acting as executor or
         administrator is a U.S. Person if:

         (i)      an executor or administrator of the estate who is not a U.S.
                  Person has sole or shared investment discretion with respect
                  to the assets of the estate; and

         (ii)     the estate is governed by foreign law;

(c)      any trust of which any professional fiduciary acting as trustee is a
         U.S. Person, if a trustee who is not a U.S. Person has sole or shared
         investment discretion with respect to the trust assets, and no
         beneficiary of the trust (and no settlor if the trust is revocable) is
         a U.S. Person;

(d)      an employee benefit plan established and administered in accordance
         with the law of a country other than the United States and customary
         practices and documentation of such country;

(e)      any agency or branch of a U.S. Person located outside the United States
         if:

                                                                              19

<PAGE>

         (i)      the agency or branch operates for valid business reasons; and

         (ii)     the agency or branch is engaged in the business of insurance
                  or banking and is subject to substantive insurance and banking
                  regulation, respectively, in the jurisdiction where located;
                  and

(f)      the International Monetary Fund, the International Bank for
         Reconstruction and Development, the Inter-American Development Bank,
         the Asian Development Bank, the African Development Bank, the United
         Nations, and their agencies, affiliates and pension plans, and any
         other similar international organisations, their agencies, affiliates
         and pension plans.

'UNITED STATES' means the United States of America, its territories and
possessions, any State of the United States, and the District of Colombia.

'US SECURITIES ACT' means United States Securities Act of 1933, as amended.

REFERENCES TO CURRENCY, INCLUDING $, CENTS AND A$ ARE REFERENCES TO AUSTRALIA
CURRENCY UNLESS OTHERWISE STATED BY, FOR EXAMPLE, REFERENCES TO US$.

20

<PAGE>

SECTION 5 - AUTHORISATION

Each Director has consented to the lodgment of this Prospectus with ASIC.

                                                                              21