Wntversity of Toronto

TORONTO 5, CANADA

DEPARTMENT OF BOTANY October 19, 1951

Dr. Joshua Lederberg,

The Department of Genetics,
The University of Wisconsin,
College of Agriculture,
MADISON, 6, Wis,

Dear Lederberg:

I am afraid I am badly in arrears, Many thanks
for your letter with the microfilm and information on more recent
experiments,

On receipt I scribbled down a largish number of
comments and planned to digest and transmit at least some of these,
Meanwhile, however, a rather hectic term has started and rather
than delay indefinitely, I should discharge myself of the minimum
obligations,

Enclosed is a draft M.S. with the maAterial on
bacterial crosses, The paper was submitted to Genetics about
three weeks ago and is virtually unchanged from the draft. Tables
and figures you have already. The discussion is still long and
extended to cover your interchange idea, It is liberally dotted
with references to "Lederberg, personal communication" (C.S.H.
material) and I would like to ask your formal permission to use
these, Any comments on the M.S. will be appreciated.

At the moment I find myself explpring Ascomycete cytology,
trying (probably like everybody else) DeLamaters staining and mounting
methods. The bacteria are completely shelved for the present although
I am tempted to explore the backcross possibilities and the validity
of the interchange map by the approach suggested on p. 19 of the

draft M.S.
Best regards to Esther,
Sincerely,
KHR /MGM K. H. Rothfels.

P.S. Incase m£ a slip in your M.S. was overlooked: The improbable
explanation of Mal twins should read - negative chromosome
and positive chromatid interference rather than the reverse,

KK