[DECHERT LLP DRAFT]

August 4, 2003

Mayer, Brown, Rowe & Maw LLP
1675 Broadway
New York, NY  10019

Re: Registration Statement on Form N-14

Ladies and Gentlemen:

We have acted as special Massachusetts counsel to Morgan Stanley Developing
Growth Securities Trust, a Massachusetts business trust ("Developing Growth"),
in connection with Developing Growth's Registration Statement on Form N-14 (the
"Registration Statement") to be filed with the Securities and Exchange
Commission (the "Commission") under the Securities Act of 1933, as amended (the
"Securities Act"), relating to the transfer of substantially all the assets of
Morgan Stanley New Discoveries Fund, a Massachusetts business trust ("New
Discoveries"), to Developing Growth in exchange for the issuance of shares of
beneficial interest of Developing Growth, par value $0.01 per share (the
"Shares"), and the assumption of New Discoveries' liabilities by Developing
Growth pursuant to the terms of an Agreement and Plan of Reorganization dated as
of July 31, 2003 (the "Agreement") by and between Developing Growth and New
Discoveries. The number of Shares to be issued are to be determined as provided
in Section 2.3 of the Agreement. This opinion is being furnished to you at your
request in connection with the filing of the Registration Statement.

In connection with the opinions set forth herein, you have provided to us
originals, copies or facsimile transmissions of, and we have reviewed and relied
upon, among other things: a copy of the Registration Statement; a copy of the
Agreement; the Amended and Restated By-Laws of Developing Growth dated April 24,
2003 (the "By-Laws"); and a Certificate of the Assistant Secretary of Developing
Growth dated August 1, 2003 with respect to certain resolutions of the Board of
Trustees and certain other factual matters. In addition, we have reviewed and
relied upon originals or copies, certified or otherwise identified to our
satisfaction, of: the Declaration of Trust of Developing Growth, as amended,
certified by the Secretary of the Commonwealth of Massachusetts; and a
Certificate issued by the Secretary of the Commonwealth of Massachusetts dated
August 1, 2003 with respect to Developing Growth. We have assumed that the
By-Laws have been duly adopted by the Trustees.

In rendering this opinion we have assumed, without independent verification, (i)
the due authority of all individuals signing in representative capacities and
the genuineness of signatures, (ii) the authenticity, completeness and continued
effectiveness of all documents or copies furnished to us, (iii) that any
resolutions provided have been duly adopted by the Trustees, (iv) that the facts
contained in the instruments and certificates or statements of public officials,
officers and representatives of Developing Growth or New Discoveries on which we
have relied for the purposes of this opinion are true and correct, and (v) that
no amendments, agreements, resolutions or actions have been approved, executed
or adopted which would limit, supersede or modify the items described above. We
have also examined





Mayer, Brown, Rowe & Maw LLP
August 4, 2003
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such documents and questions of law as we have concluded are necessary or
appropriate for purposes of the opinions expressed below. Where documents are
referred to in resolutions approved by the Trustees, or in the Registration
Statement, we assume such documents are the same as in the most recent form
provided to us, whether as an exhibit to the Registration Statement or
otherwise. When any opinion set forth below relates to the existence or standing
of Developing Growth, such opinion is based entirely upon and is limited by the
items referred to above, and we understand that the foregoing assumptions,
limitations and qualifications are acceptable to you.

Based upon the foregoing, and with respect to Massachusetts law only (except
that no opinion is herein expressed with respect to compliance with the
securities, or "blue-sky," laws of Massachusetts), to the extent that
Massachusetts law may be applicable, and without reference to the laws of any of
the other several states or of the United States of America, including state and
federal securities laws, we are of the opinion that:

1.      Developing Growth has been duly formed and is validly existing as a
business trust under the laws of the Commonwealth of Massachusetts; and

2.      the Shares registered under the Securities Act in the Registration
Statement when issued in accordance with the terms described in the Registration
Statement and the Agreement will be legally issued, fully paid and
non-assessable by Developing Growth (except for the potential liability of
shareholders described in Developing Growth's Statement of Additional
Information dated November 29, 2002 under the caption "Capital Stock and Other
Securities").

The opinions expressed herein are limited to the laws of the Commonwealth of
Massachusetts as described above. We express no opinion herein with respect to
the effect or applicability of the law of any other jurisdiction. We express no
opinion as to any other matter other than as expressly set forth above and no
other opinion is intended or may be inferred herefrom. The opinions expressed
herein are given as of the date hereof and we undertake no obligation and hereby
disclaim any obligation to advise you of any change after the date of this
opinion pertaining to any matter referred to herein.

Very truly yours,