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                                                                     EXHIBIT 4.2


                          FORM OF ASSUMPTION AGREEMENT

         This Assumption Agreement is made and entered into effective as of
December 29, 2000 (the "Effective Time"), by and between TradeStation Group,
Inc., a Florida corporation (the "Company"), and ______________________ (the
"Holder"), in connection with that certain Agreement and Plan of Merger and
Reorganization (the "Merger Agreement") dated January 19, 2000, by and among the
Company, Omega Research, Inc., a Florida corporation ("Omega"),
onlinetradinginc.com corp., a Florida corporation ("Online"), Omega Acquisition
Corporation, a Florida corporation ("Omega Merger Sub"), and Onlinetrading
Acquisition Corporation, a Florida corporation ("Online Merger Sub"), pursuant
to which, among other things, Online Merger Sub merged with and into Online, and
Online became a wholly-owned subsidiary of the Company effective as of the
Effective Time.

                                   WITNESSETH:

         WHEREAS, Online has previously issued to Holder that certain
Underwriters' Warrant No. ___, dated as of June 10, 1999 (the "Underwriters'
Warrant"), whereby Online granted to Holder the right to acquire up to
___________ shares of Online's common stock, $.01 par value ("Online Common
Stock"), at an exercise price of $11.55 per share (collectively the "Warrants"),
and the Warrants represent all of the warrants to acquire Online Common Stock
granted to Holder prior to the Merger.

         NOW, THEREFORE, pursuant to the Merger Agreement and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Company and Optionee hereby agree that:

         1. As of the Effective Time, all of the Warrants are hereby assumed by
the Company subject to the terms of the Underwriters' Warrant as and to the
extent modified by the Merger Agreement.

         2. In accordance with Section 6.13(c) of the Merger Agreement, the
Warrants so assumed continue to have, and be subject to, the same terms and
conditions as set forth in the Underwriters' Warrant immediately prior to the
Effective Time, except as follows: (i) such Warrants will be exercisable for
___________ shares of common stock, $.01 par value, of the Company ("Company
Common Stock"), which equals the product of the number of shares of Online
Common Stock that were issuable upon exercise of the Warrants immediately prior
to the Effective Time multiplied by 1.7172 (the "Exchange Ratio") and rounded
down to the nearest whole number of shares of Company Common Stock, in lieu of
Online Common Stock; (ii) the per share exercise price for the shares of Company
Common Stock issuable upon exercise of such assumed Warrants is $6.73, which
equals the quotient determined by dividing the exercise price per share of
Online Common Stock at which such Warrants were exercisable immediately prior to
the Effective Time by the Exchange Ratio, rounded up to the nearest whole cent;
(iii) any notice required to be delivered pursuant to the terms and conditions
set forth in the Underwriters' Warrant shall be delivered to the offices of
TradeStation Group, Inc., 8050 S.W. 10th Street, Plantation, Florida 33324,
Attention: Chief Financial Officer; and (iv) all references in the Underwriters'
Warrant to "Company" shall hereafter refer to TradeStation Group, Inc. except
where the context clearly indicates that "Company" should continue to refer to
onlinetradinginc.com corp.


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         IN WITNESS WHEREOF, the Company and Holder acknowledge that this
Assumption Agreement is effective as of the date first written above.

HOLDER                                    TradeStation Group, Inc.

______________________________            By:___________________________________

Name:_________________________            Name: ________________________________

Address:______________________            Title: _______________________________

______________________________


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