Exhibit 3.4.2
                            CERTIFICATE OF AMENDMENT
                                       TO
                           CERTIFICATE OF DESIGNATION
                                       OF
                                   PREFERENCES
                                       OF
                      SERIES B CONVERTIBLE PREFERRED STOCK
                                       OF
                             LYNX THERAPEUTICS, INC.


         Lynx Therapeutics, Inc., a corporation organized and existing under and
by virtue of the General  Corporation Law of the State of Delaware,  DOES HEREBY
CERTIFY:

         FIRST:  The name of the  corporation  is Lynx  Therapeutics,  Inc. (the
"Corporation").

         SECOND:  The date on which  the  Certificate  of  Incorporation  of the
Corporation first was filed with the Secretary of State of the State of Delaware
is February 18, 1992.

         THIRD: The Board of Directors, acting in accordance with the provisions
of Sections 151 and 242 of the General Corporation Law of the State of Delaware,
adopted  resolutions to amend  paragraphs  4(a) and 4(b) of Section B of Article
THIRD of the  "Certificate of Designation of Preferences of Series B Convertible
Preferred  Stock  of Lynx  Therapeutics,  Inc."  to read in  their  entirety  as
follows:

         "4. CONVERSION.

                  The holders of the Series B Convertible  Preferred Stock shall
have conversion rights as follows (the "Conversion Rights"):

         a.  Mandatory  Conversion.  On March 31,  1998,  each share of Series B
Convertible Preferred Stock shall automatically convert into the number of fully
paid and nonassessable  shares of Common Stock which results from dividing $5.00
by the Series B Conversion Price (as hereinafter defined) per share in effect at
the  time of  conversion  (the  Automatic  Conversion").  The  initial  Series B
Conversion Price shall be $.50. The Series B Convertible  Preferred Stock is not
otherwise convertible. The number of shares of Common Stock into which one share
of Series B Convertible Preferred Stock may be converted hereinafter is referred
to as the "Conversion Rate."

                  b.  Mechanics of  Conversion.  Upon the Automatic  Conversion,
each  holder  of  Series B  Convertible  Preferred  Stock  shall  surrender  the
certificate or certificates for such shares, duly endorsed, at the office of the
Corporation  or of any  transfer  agent for the Series B  Convertible  Preferred
Stock,  or notify the  Corporation  or its  transfer  agent  that such  Series B
Convertible Preferred Stock certificates have been lost, stolen or destroyed and
execute  an  agreement   satisfactory   to  the  Corporation  to  indemnify  the
Corporation  from any loss incurred by it in connection with such  certificates.
The Corporation shall then, as soon as is practicable, issue and deliver at such
office to such  holder  of  Series B  Convertible  Preferred  Stock,  or to such
holder's  nominee or nominees,  a certificate or certificates  for the number of
shares of Common Stock to which such holder is entitled."

         FOURTH: Thereafter, pursuant to a resolution of the Board of Directors,
this  Certificate  of  Amendment  was  submitted  to the  holders  of  Series  B
Convertible  Preferred  Stock for their approval in accordance with Sections 228
and 242 of the  General  Corporation  Law of the State of  Delaware  and written
notice  has been  given  to all such  stockholders  who  have not  consented  as
provided  in  Section  228(d)  of the  General  Corporation  Law of the State of
Delaware.

                                      53.
<PAGE>

                  IN WITNESS WHEREOF,  Lynx  Therapeutics,  Inc. has caused this
Certificate  of  Amendment  to be  signed  by its Chief  Executive  Officer  and
attested by its Secretary this 30th day of September, 1997.

                                                LYNX THERAPEUTICS, INC.


                                                /s/ Sam Eletr
                                                -------------------------------
                                                Sam Eletr
                                                Chief Executive Officer


ATTEST:


/s/ James C. Kitch
----------------------------
James C. Kitch
Secretary


                                      54.