SECURITIES AND EXCHANGE COMMISSION
                     Washington, D.C. 20549
                        ________________

                          SCHEDULE 13G/A
                        ________________

     INFORMATION STATEMENT PURSUANT TO RULES 13d-1 AND 13d-2
            UNDER THE SECURITIES EXCHANGE ACT OF 1934

                       (AMENDMENT NO. 1)*

                        Cytyc Corporation
                         (NAME OF ISSUER)

                  Common Stock, $0.01 par value
                  (TITLE OF CLASS OF SECURITIES)

                           232946 10 3
                         (CUSIP NUMBER)





__________________

*    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 the disclosures provided in a prior cover page.

     The information required in the remainder of this cover page shall not
     be deemed to be "filed" for the purpose of Section 18 of the Securities
     Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of
     that section of the Act but shall be subject to all other provisions of
     the Act (however, see the Notes).

                                   PAGE 1 OF 5 PAGES 




                                       13G/A

CUSIP No.  232946 10 3
_____________________________________________________________________________
     (1)  NAME OF REPORTING PERSON 
          S.S. OR I.R.S. IDENTIFICATION NO. 
          OF ABOVE PERSON 
          Ardsley Advisory Partners
_____________________________________________________________________________
     (2)  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP ** 
                                                                    (a)  [ ] 
                                                                    (b)  [x] 
_____________________________________________________________________________
     (3)  SEC USE ONLY 

_____________________________________________________________________________
     (4)  CITIZENSHIP OR PLACE OF ORGANIZATION 
          Connecticut
_____________________________________________________________________________

NUMBER OF      (5)  SOLE VOTING POWER 
                    0
SHARES         ______________________________________________________________

BENEFICIALLY   (6)  SHARED VOTING POWER
                    0
OWNED BY       ______________________________________________________________

EACH           (7)  SOLE DISPOSITIVE POWER 
                    0
REPORTING      ______________________________________________________________

PERSON WITH    (8)  SHARED DISPOSITIVE POWER 
                    0
_____________________________________________________________________________
     (9)  AGGREGATE AMOUNT BENEFICIALLY OWNED
          BY EACH REPORTING PERSON 
          0
_____________________________________________________________________________
    (10)  CHECK BOX IF THE AGGREGATE AMOUNT 
          IN ROW (9) EXCLUDES CERTAIN SHARES **                          [ ] 
_____________________________________________________________________________
    (11)  PERCENT OF CLASS REPRESENTED 
          BY AMOUNT IN ROW (9)           
          0%
_____________________________________________________________________________
    (12)  TYPE OF REPORTING PERSON **
               IA
_____________________________________________________________________________
             ** SEE INSTRUCTIONS BEFORE FILLING OUT!

                                   PAGE 2 OF 5 PAGES





                               13G/A

CUSIP No.  232946 10 3
_____________________________________________________________________________
     (1)  NAME OF REPORTING PERSON 
          S.S. OR I.R.S. IDENTIFICATION NO. 
          OF ABOVE PERSON 
          Philip J. Hempleman
_____________________________________________________________________________
     (2)  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP ** 
                                                                    (a)  [ ] 
                                                                    (b)  [x] 
_____________________________________________________________________________
     (3)  SEC USE ONLY 

_____________________________________________________________________________
     (4)  CITIZENSHIP OR PLACE OF ORGANIZATION 
          United States
_____________________________________________________________________________

NUMBER OF      (5)  SOLE VOTING POWER 
                    0
SHARES         ______________________________________________________________

BENEFICIALLY   (6)  SHARED VOTING POWER
                    0
OWNED BY       ______________________________________________________________

EACH           (7)  SOLE DISPOSITIVE POWER 
                    0
REPORTING      ______________________________________________________________

PERSON WITH    (8)  SHARED DISPOSITIVE POWER 
                    0
_____________________________________________________________________________
     (9)  AGGREGATE AMOUNT BENEFICIALLY OWNED
          BY EACH REPORTING PERSON 
          0
_____________________________________________________________________________
    (10)  CHECK BOX IF THE AGGREGATE AMOUNT 
          IN ROW (9) EXCLUDES CERTAIN SHARES **                          [ ] 
_____________________________________________________________________________
    (11)  PERCENT OF CLASS REPRESENTED 
          BY AMOUNT IN ROW (9)           
          0%
_____________________________________________________________________________
    (12)  TYPE OF REPORTING PERSON **
               IN
_____________________________________________________________________________
             ** SEE INSTRUCTIONS BEFORE FILLING OUT!

                                   PAGE 3 OF 5 PAGES






The Schedule 13G initially filed for the year ended December 31, 1996 of 
(i) Ardsley Advisory Partners and (ii) Philip J. Hempleman relating to the
 common stock, par value $.001 (the "Common Stock"), issued by Cytyc
Corporation (the "Company") is hereby amended as follows:

ITEM 4.   OWNERSHIP.

          Not applicable.

ITEM 5.   OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS.

          If this statement is being filed to report the fact that as of the 
date hereof the reporting person has ceased to be the beneficial owner of
more than five percent of the class of securities, check the following [x]

                                   PAGE 4 OF 5 PAGES









ITEM 10.  CERTIFICATION.  (if filing pursuant to Rule 13d-1(b))

          By signing below Ardsley Advisory Partners and Philip J. Hempleman 
certify that, to the best of their knowledge and belief, the securities
referred above were acquired in the ordinary course of business, were not
acquired for the purpose of and do not have the effect of changing or
influencing the control of the issuer of such securities and were not
acquired in connection with or as a participant in any transaction having
such purposes or effect.




                            SIGNATURE

          After reasonable inquiry and to the best of their knowledge and
belief, the undersigned certify that the information set forth in this
statement is true, complete and correct.




                              February __, 1998




                              /s/ Philip J. Hempleman
                              -----------------------
                              Philip J. Hempleman, as
                              Managing Partner of 
                              Ardsley Advisory Partners



                              /s/ Philip J. Hempleman
                              -----------------------
                              Philip J. Hempleman


                                   PAGE 5 OF 5 PAGES