<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D. C. 20549
                           --------------------------

                                    FORM 10-K

                Annual Report Pursuant to Section 13 or 15(d) of
                       The Securities Exchange Act of 1934
                            -------------------------

       For the fiscal year ended:                    Commission file number:
           DECEMBER 31, 1998                               333-29015

                          MERRILL LYNCH DEPOSITOR, INC.
            (ON BEHALF OF PUBLIC STEERS(R) SERIES 1998 MCIC-P1 TRUST)
             (Exact name of registrant as specified in its charter)

               DELAWARE                                          13-3891329
           (State or other                                   (I. R. S. Employer
           jurisdiction  of                                  Identification No.)
            incorporation)

        WORLD FINANCIAL CENTER,                                     10281
          NEW YORK,  NEW YORK                                    (Zip Code)
         (Address of principal
          executive offices)
                                --------------------------

               Registrant's telephone number, including area code:
                                 (212) 449-1000

Securities registered pursuant to Section 12(b) of the Act:    NOT APPLICABLE

Securities registered pursuant to Section 12(g) of the Act:   NOT APPLICABLE

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the Registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.
                                    Yes [X]               No [ ]

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this form 10-K or any amendment to this
form 10-K.  [X]
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State the aggregate market value of the voting and non-voting common equity held
by non-affiliates of the registrant. The aggregate market value shall be
computed by reference to the price at which the common equity was sold, or the
average bid and asked prices of such common equity, as of a specified date
within 60 days prior to the date of filing. (See definition of affiliate in Rule
405, 17 CFR 230.405.)

                                 NOT APPLICABLE

Indicate the number of shares outstanding for each of the registrant's class of
common stock, as of the latest practicable date.

                                 NOT APPLICABLE

                           Documents Incorporated by Reference

                                      NONE

PART I.

ITEM 1.           BUSINESS.

                  Not Applicable.

ITEM 2.           PROPERTIES.

                  Not Applicable.

ITEM 3.           LEGAL PROCEEDINGS.

                  None.

ITEM 4.           SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

                  None.

PART II.

ITEM 5.           MARKET FOR REGISTRANT'S COMMON EQUITY AND RELATED
                  STOCKHOLDER MATTERS.

                  The Trust Certificates issued by Public STEERS(R) Series 1998
                  MCIC-P1 Trust are represented by one or more physical
                  certificates registered in the name of Cede & Co., the nominee
                  of the Depository Trust Company.

                  To the best knowledge of registrant, there is no established
                  public trading market for the Trust Certificates.

ITEM 6.           SELECTED FINANCIAL DATA.

                  Not Applicable.
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ITEM 7.           MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION
                  AND RESULTS OF OPERATIONS.

                  Not Applicable.

ITEM 7A.          QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

                  Not Applicable.

ITEM 8.           FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA.

                  Not Applicable.

ITEM 9.           CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING
                  AND FINANCIAL DISCLOSURE.

                  Not Applicable.

PART III.

ITEM 10.          DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT.

                  Not Applicable.

ITEM 11.          EXECUTIVE COMPENSATION.

                  Not Applicable.

ITEM 12.          SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND 
                  MANAGEMENT.

                  (a)      None.
                  (b)      Not Applicable.
                  (c)      Not Applicable.

ITEM 13.          CERTAIN RELATIONSHIPS AND RELATED PARTY TRANSACTIONS.

                  None.

PART IV.

ITEM 14.          EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS OF 
                  FORM 8K.

                  Trustee's report in respect of the June 15, 1998 distribution
                  to holders of the Public STEERS(R) Series 1998 MCIC-P1 Trust
                  Class A Certificates herein by reference as exhibits to
                  Registrant's Current Report on Form 8K filed with the
                  Securities and Exchange Commission on June 16, 1998.

                  Trustee's report in respect of the December 15, 1998
                  distribution to holders of the Public STEERS(R) Series 1998
                  MCIC-P1 Trust Class A Certificates 
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                  herein by reference as exhibits to Registrant's Current Report
                  on Form 8K filed with the Securities and Exchange Commission
                  on December 28, 1998.





                                   SIGNATURES

                  Pursuant to the requirements of the Securities Exchange Act of
                  1934, the registrant has duly caused this report to be signed
                  on its behalf by the undersigned, hereunto duly authorized.


                                             MERRILL LYNCH DEPOSITOR, INC.
                                             as Depositor for the Trust

         Date:    04/13/99                   By:      /s/ Barry Finkelstein
                                                      Name:    Barry Finkelstein
                                                      Title:   President
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                                  EXHIBIT INDEX


                  Trustee's report in respect of the June 15, 1998 distribution
                  to holders of the Public STEERS(R) Series 1998 MCIC-P1 Trust
                  Class A Certificates herein by reference as exhibits to
                  Registrant's Current Report on Form 8K filed with the
                  Securities and Exchange Commission on June 16, 1998.

                  Trustee's report in respect of the December 15, 1998
                  distribution to holders of the Public STEERS(R) Series 1998
                  MCIC-P1 Trust Class A Certificates  herein by reference as
                  exhibits to Registrant's Current Report on Form 8K filed with
                  the Securities and Exchange Commission on December 28, 1998.