[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.

                                                                  EXHIBIT 10.7.4

                               FOURTH AMENDMENT TO
                  TECHNOLOGY DEVELOPMENT AND SERVICES AGREEMENT


            This Fourth Amendment to Technology Development and Services
Agreement (this "Amendment") is made and entered into as of March 31, 2002 by
and between Lynx Therapeutics, Inc., a Delaware corporation, and its
majority-owned subsidiaries (including Spectragen, Inc.) (collectively, "Lynx"),
and Aventis CropScience GmbH, a German corporation ("CropScience" and, formerly,
"AgrEvo").

                                    RECITALS

            A. The parties hereto (or their predecessors) previously entered
into that certain Technology Development and Services Agreement dated as of
October 2, 1995, as amended by the First Amendment to Technology Development and
Services Agreement dated as of September 1, 1997, as further amended by the
Amended and Restated First Amendment to Technology Development and Services
dated as of May 1, 1998, the Second Amendment to Technology Development and
Services Agreement dated as of March 1, 1999, the Third Amendment to Technology
Development and Services Agreement dated as of December 1, 1999 (the "Third
Amendment"), the letter agreement dated March 16, 2001, the letter agreement
dated November 8, 2001 and the letter agreement dated December 13, 2001
(collectively, as amended, the "Original Agreement").

            B. The Original Agreement [ * ] its subscription pursuant to Section
2.4. of the Original Agreement.

            C. Pursuant to the Original Agreement, the parties jointly developed
certain technologies for use in identifying (among other things) whether [ * ].

            D. The parties desire to create a Fourth Amendment to Technology
Development and Services Agreement to extend the term of the Original Agreement
and incorporate certain terms and conditions relating to the new technology, all
as described more fully herein.

                                    AGREEMENT

            NOW, THEREFORE, in consideration of the foregoing premises and the
covenants and promises contained in this Agreement, the parties hereby agree as
follows:

      1. [ * ] Technology. The Original Agreement shall be amended by adding new
Sections 1.7, 1.8 and 1.9 as follows:





            1.7 "[ * ] Technology" means a Megasort based assay of a [ * ],
      which shall have such performance characteristics as identified from time
      to time by the JRC, as well as any additional technology arising out of
      performance under the [ * ] Development Plan.

            1.8 "[ * ] Development Plan" means the science plan agreed upon by
      CropScience and approved by Lynx relating to the joint development of the
      [ * ] Technology, pursuant to which the [ * ] Technology will be developed
      within [ * ] from the date of execution of this Amendment.

            1.9 "Product Launch" means such time as the JRC determines the [ * ]
      Technology may be offered commercially to the public market.

            1.10 "Net Profits" shall mean Net Sales or Revenues less: Cost of
      Sales or Revenues; and marketing, selling and general and administrative
      expenses directly related or appropriately allocable to generating Net
      Sales or Revenues.

            1.11 "Net Sales" or "Revenues" shall mean gross sales or revenues
      received by Lynx Therapeutics, Inc. and/or its divisions, affiliates,
      business units, subsidiaries and sublicensees from: (i) the sale of
      products using or incorporating the [ * ] Technology; and/or from (ii)
      licensing-out the [ * ] Technology; and/or from (iii) the services
      provided by Lynx to third parties by making use of the [ * ] Technology
      sold in arm's length transactions with unaffiliated third parties in the
      ordinary course of business, after deduction of the following items: (a)
      trade, cash and quantity discounts or rebates actually allowed or taken;
      (b) credits or allowances given or made for rejection or return of
      previously sold products or for retroactive price reductions; (c) any tax
      or government charge (other than an income tax) levied on the sale,
      transportation or delivery of products and borne by the seller thereof;
      (d) and charges for freight and insurance directly related to distribution
      of the products or provision of services. Net sales shall not include
      sales or transfers of the product or service between Lynx and its
      divisions, affiliates, business units, subsidiaries and sublicensees
      unless such sale is considered a final sale of such product or service

            1.12 "Cost of Sales or Revenues" shall mean the sum of (a) the costs
      of goods produced and/or services performed, determined in accordance with
      generally accepted accounting principles in the United States as applied
      by Lynx, including but not limited to costs of direct labor, direct
      materials, and other direct items, as well as allocable overhead; and (b)
      any reasonable royalties due to third parties with respect to licensed-in
      technology and that are directly allocable to the use of such technology
      in the application of [ * ] Technology.



                                       2


      2. Ownership of [ * ] Technology. Section 2.3 of the Original Agreement
shall be amended to add second and third paragraphs to read as follows:

            Notwithstanding anything to the contrary herein, the parties
      acknowledge and agree that the [ * ] Technology is a new invention
      developed and jointly owned by Lynx Therapeutics, Inc. and Aventis
      CropScience N.V., an affiliate of CropScience pursuant to this Agreement.
      For the avoidance of doubt, the definition of "Confidential Information"
      set forth in Article 4 hereof includes the [ * ] Technology and know-how
      and other information related thereto. CropScience hereby grants to Lynx
      Therapeutics, Inc. an exclusive, non-assignable license to its rights in
      and to the [ * ] Technology to make, use, have made and sell products
      using or incorporating the [ * ] Technology, any patents or patent
      applications relating thereto and all related know-how.

      In consideration of this license grant, Lynx Therapeutics Inc agrees to
      pay to CropScience a royalty of [ * ] per cent ([ * ] %) on the Net
      Profits. Lynx Therapeutics, Inc. shall (i) diligently proceed with the
      development, manufacture and sale of services or products incorporating or
      based on the [ * ] Technology; and (ii) reasonably fill the market demand
      for such services or products following the Product Launch; and (iii)
      obtain all necessary governmental approvals for the manufacture, use and
      sale of such services or products. If Lynx Therapeutics, Inc. fails to
      perform any of the foregoing obligations, CropScience shall be granted
      sufficient rights by Lynx Therapeutics, Inc. to use and exploit the [ * ]
      Technology, any patents or patent applications relating thereto and all
      related know-how.

      Within ninety (90) days from the end of the calendar year in which Product
      Launch occurred and thereafter as long as royalties are due by Lynx
      Therapeutics, Inc., Lynx Therapeutics, Inc. shall provide CropScience a
      statement of Net Profits received and the applicable royalties in
      accordance with this Section 2. In addition, Lynx Therapeutics, Inc. shall
      keep, and shall require its affiliates and sublicensees to keep, accurate
      and correct records of all products manufactured, used and sold, license
      income received and services provided by Lynx Therapeutics, Inc. under
      this Amendment. Such records shall be retained by Lynx Therapeutics, Inc.
      for at least three (3) years following a given period. All records shall
      be available during normal business hours for inspection, upon at least
      thirty (30) days' prior written notice, at the expense of CropScience by
      an independent certified public accountant selected by CropScience for the
      sole purpose of verifying reports and payments. Such inspector shall not
      disclose to CropScience any information other than information relating to
      the accuracy of reports and payments made under this Amendment or other
      compliance issues. In the event that any such inspection shows an under
      reporting and underpayment in excess of ten percent (10%), then Lynx
      Therapeutics, Inc. shall pay the costs of the audit as well as any
      additional sum that would have been payable to CropScience had Lynx
      Therapeutics, Inc. reported correctly. For underpayment not in excess of
      ten percent (10%), Lynx Therapeutics, Inc. shall pay the difference within
      thirty (30) days without inspection cost.



                                       3


      All royalties due to CropScience shall be paid in United States Dollars
      within ninety (90) days from the end of the calendar year in which the net
      profits where received by Lynx Therapeutics, Inc. to the following bank
      account: [ * ] or to such other bank account notified to Lynx
      Therapeutics, Inc. from time to time. In the event payments are not
      received by CropScience when due, Lynx Therapeutics, Inc. shall pay to
      CropScience interest charges of one and a half percent (1.5%) per month
      without obligation for CropScience to serve prior notice.

            Lynx Therapeutics, Inc. shall have the first right, at its own
      expense, to prepare and file patent applications and maintain patents
      relating to the [ * ] Technology, and improvements, modifications or
      patentable know-how relating thereto, all in the joint name of Lynx
      Therapeutics, Inc. and Aventis CropScience N.V.

      3. Milestone Payment to Lynx. Section 2.4 of the Original Agreement shall
be deleted in its entirety and replaced with the following:

            2.4 CropScience shall pay to Lynx [ * ] U.S. Dollars ($[ * ]) upon
      the Product Launch, which milestone payment shall be set-off against the
      prepayments made by CropScience as described in Section 3.9 hereof.

      4. CropScience Subscription. Section 3.9 of the Original Agreement shall
be deleted in its entirety and replaced with the following:

            3.9 The parties acknowledge that CropScience has made prepayments
      totaling [ * ] U.S. Dollars (US $[ * ]) to Lynx in exchange for Analyses
      to be provided by Lynx and Lynx has performed Analyses with a total Value
      of $[ * ] for CropScience, which leaves a remaining credit of $[ * ]
      available (the "Credit") under the Agreement as of March 31, 2002. During
      the term of this Amendment, CropScience shall be entitled to receive from
      Lynx, without additional payment until the Credit has been exhausted,
      services under the [ * ] Development Plan and Analyses having an aggregate
      Value equal to $[ * ]. Irrespective of any services actually provided, (i)
      prior to the Product Launch, Lynx shall be deemed to have provided
      services under the [ * ] Development Plan to CropScience having an
      aggregate Value of [ * ] U.S. Dollars (US $[ * ]) during each calendar [ *
      ], commencing, [ * ], which amount shall be charged by Lynx against the
      Credit, and (ii) subsequent to the Product Launch, Lynx shall be deemed to
      have provided Analyses to CropScience having an aggregate Value of [ * ]
      U.S. Dollars (US $[ * ]) during each calendar [ * ], which amount shall be
      charged by Lynx against the Credit, until such time as the Credit has been
      exhausted. The "Value" of any single Analysis performed by Lynx for
      CropScience under the Agreement shall be equal to [ * ].

      5. Joint Research Committee. New Sections 3.10, 3.11, 3.12 and 3.13 shall
be added to the Original Agreement to read as follows:



                                       4


            3.10 A Joint Research Committee ("JRC") shall be formed by the
      parties which shall comprise two (2) representatives from each of Lynx and
      CropScience or one of its Affiliates, each of whom shall be experienced in
      a relevant aspect of the [ * ] Technology. The parties shall designate
      their representatives to the JRC within ten (10) days of the date of this
      Amendment. Members of the JRC shall serve on such terms as shall be
      determined by the party designating such person for membership on the JRC.
      An alternate member designated by a party may serve temporarily in the
      absence of a member designated by such party. Each party shall bear its
      own costs for participating in the JRC. Each party may replace any of its
      representatives to the JRC at any time, and will inform the other party
      thereof in writing.

                  (a) The JRC shall hold meetings at such times and places as
      shall be determined by the JRC, but no less than once in every [ * ]. The
      JRC may conduct meetings in person or by teleconference or other means of
      communication. The JRC may, by mutual consent of the representatives of
      each party, invite other personnel of their organization to attend
      meetings of the JRC. On an alternating basis, the representatives of each
      Party shall be responsible for preparing, within a reasonable period, the
      minutes of each JRC meeting, such minutes to include in reasonable detail
      any actions taken by the JRC, issues requiring resolution, and resolutions
      of previously reported issues. The minutes shall be approved in writing by
      authorized representatives of Lynx and CropScience.

                  (b) Actions by the JRC pursuant to this Agreement shall be
      taken only with the unanimous approval of all of the representatives of
      the JRC, and any disputed matters shall be presented to executives of each
      of the parties for resolution. The JRC shall have no power to amend this
      Amendment and shall have only such powers as are specifically delegated to
      it hereunder. The JRC shall (i) encourage and facilitate ongoing
      cooperation and information and materials exchange between the parties as
      necessary for performance of the [ * ] Development Plan; (ii) evaluate
      progress and results of work under the [ * ] Development Plan and make
      recommendations to the parties for changes in the [ * ] Development Plan,
      if necessary; and (iii) evaluate and thereafter provide recommendations to
      the parties regarding whether milestone activities have been completed.

            3.11. Promptly following execution of this Amendment, the parties
      shall use commercially reasonable efforts to carry out the objectives of
      the [ * ] Development Plan. Such efforts will include devoting a level of
      manpower to the tasks of the [ * ] Development Plan that is appropriate in
      amount and level of skill to provide a reasonable expectation that the
      [ * ] Development Plan will be completed and Product Launch commenced
      within [ * ]. Subject to the term of



                                       5


      this Amendment, each party shall bear its own costs of carrying out its
      obligations under the [ * ] Development Plan.

            3.12 As of Product Launch, CropScience shall use commercially
      reasonable efforts to introduce, [ * ] all in the joint name of Lynx and
      CropScience. CropScience shall seek inclusion of the [ * ]. Only in the
      event CropScience fails to perform under this Section 3.12 may Lynx try to
      secure such inclusion.

            3.13 No party shall submit for written or oral publication or
      presentation any manuscript, abstract, writing, printed material or the
      like which includes data or any other information generated under the [ *
      ] Development Plan without first obtaining the prior written consent of
      the other party, which consent shall not be unreasonably withheld or
      delayed; provided, however, that if in the opinion of the non-publishing
      party, it is believed that any such publication contains (a) a patentable
      development, submission for publication shall be delayed to permit the
      filing of appropriate patent application or patent applications, but in no
      event shall such delay exceed ninety (90) days from the time either party
      receives such advanced copy of the proposed publication, or (b) a party's
      Confidential Information, such information shall be deleted from the
      proposed publication as requested in writing.

      6. Expiration. The first sentence of Section 5.1 of the Third Amendment
shall be deleted in its entirety.

      7. Notices. Section 7.6 of the Original Agreement shall be amended by
replacing the addresses for notices to the parties with the following:

      If to Lynx:

            Lynx Therapeutics, Inc.
            25861 Industrial Blvd.
            Hayward, CA 94545
            Fax:  510-670-9302
            Attn:  President and Chief Executive Officer

      If to CropScience:

            Aventis CropScience GmbH
            Industriepark Hochst - K 607
            Bruningstrasse 50
            D-65926 Frankfurt a. Main
            Germany
            Fax: + 49 69 305 83 454
            Attn: General Counsel



                                       6


      8. Entire Agreement. The Original Agreement, together with this Amendment,
constitutes and contains the complete, final and exclusive understanding and
agreement of the parties with respect to the subject matter hereof and cancels
and supersedes any and all prior negotiations, correspondence, understandings
and agreements, whether oral or written, between the parties respecting the
subject matter hereof.

      9. Term. The term of this Amendment shall be for five years from the first
date written above and extendable upon mutual agreement and upon extension of
the Original Agreement. However, even after expiration of this Amendment, at
first request of CropScience, Lynx shall render services with respect to the [ *
] Technology to CropScience and its affiliates under terms and conditions to be
agreed upon by Lynx and CropScience, but the financial conditions of such
services shall be no more than the cost that is charged for similar assays to
third parties with a maximum of three (3) times Lynx's fully burdened cost.

      10. Governing Law. This Amendment shall be governed by and construed in
accordance with the laws of the State of California as applied to contracts
entered into and to be performed in California, without reference to conflicts
of laws.

      11. Counterparts. This Amendment may be executed in any number of
counterparts and by facsimile signature, each of which shall be an original, but
all of which together shall constitute one instrument.



                                       7


            IN WITNESS WHEREOF, the parties hereto have duly executed this
Fourth Amendment to Technology Development and Services Agreement by their duly
authorized representatives as of the date first written above.


Lynx Therapeutics, Inc.                   Aventis CropScience GmbH


By:  /s/ Norman Russell                  By:  /s/ Sjut
   -----------------------------------       -----------------------------------
Name:    Norman Russell                  Name:    Volkert Sjut
Title:   CEO                             Title:   Managing Director

                                         By:  /s/ ppa. Falcke
                                            ------------------------------------
                                         Name:    Gunther Falcke
                                         Title:   General Counsel




[ * ] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



                                       8