PHYSICAL CHEMISTRY LABORATORY,
TEL: 48536.

SOUTH PARKS ROAD

Dr J. Lederberg, OXFORD.
College of Agriculture,

University of Wisconsin, 16th February 1949
Madison 6,

U.S.A.

Dear Dr Lederterg,

Thank you very much for your interesting letter on the
subject of mutations, reversed mutations and related questions.

I should like to say that I am very much alive to the
importance of these matters and follow with great interest all
the work on genetic analysis applied to micro-organisms. In
the little essay which I was bold enough to publish in 1946 I
did in chapters 8 and 9 do my best to suggest that mutations
and more strictly adaptive changes might well be the endsof a
continuous spectrum,

In our own experience we have not so far encountered
anything which has struck us here as compellingly suggestive of
genic recombination but then we have always stuck to a very
narrow range of organisms indeed, The reason for this is I
think surmed up in the last paragraph of one of the enclosed
reprints (in the orange cover), Our angle is to explore the
potentialities of physico-chemical models and certainly not to
claim any universal validity for them.

I enclose some of the more recent reprints and trust
that you will regard them in that spirit.

Yours sincerely,

/- occa Brecon J

co f~/.