JOINT FILING AGREEMENT The undersigned hereby agree that this statement on Schedule 13D is, and any amendment thereto signed by each of the undersigned shall be, filed on behalf of each undersigned pursuant to and in accordance with the provisions of...

                             JOINT FILING AGREEMENT



          The undersigned hereby agree that this statement on Schedule 13D is,
and any amendment thereto signed by each of the undersigned shall be, filed on
behalf of each undersigned pursuant to and in accordance with the provisions of
Rule 13d-1(f)(1) under the Securities Exchange Act of 1934.



Dated:  December 31, 1997



                              WARBURG, XXXXXX VENTURES, L.P.


                               By: Warburg, Xxxxxx & Co.,
                                   General Partner



                              By: /s/Xxxxxxx Xxxxxxx
                                   Xxxxxxx Xxxxxxx, Partner



                              WARBURG, XXXXXX & CO.



                              By: /s/Xxxxxxx Xxxxxxx
                                   Xxxxxxx Xxxxxxx, Partner



                              X.X. XXXXXXX, XXXXXX & CO., LLC



                              By: /s/Xxxxxxx Xxxxxxx
                                   Xxxxxxx Xxxxxxx, Member