July 15, 1946.

Dear Kim:

How's interning- have they sappec you dry yet? What have you heard
_ from the Navy about a period of service when you're through? They jsut
sent me an HP Ensignship a couple of weeks ago. However I'm staying up here
another year with a leave of absence,

The Cold Spring Harbour Symposium this summer on Heredity and Variation
in Micrporganisms has just closed. Included was a paper by Lederberg end
Tatum on 'Novel Genotypes in Mixed Cultures of Biochemical Mutants of Bacterhat!
The evidence is quigfe conclusiv, although perhaps meagre in quantity, for
a recombination process in E, coli: we get out wild types from mixtures
of double or even téhple biochemical mutants, and we can show segregation
for phage resistance in these wilds (prototrophs). Also we have isolated
one (1) new recombinant of a recessive type: from biotin-galanine-cyst ine-lass
and threonine-proline-less a biotin-prolineless. #e're lookigg for more
obviously. ‘there was quite a fuss after the paper was presented~ I got
into an unfortunate argument with Lwoff, but everything was smoothed out
eventually. Delbrick summarized the general feeling with the statement that
there was no obvious loophole, but that more data were obviously necessary.
It was a fascinating symposium, I tried to get in touch with you but every
time I called you were out? Aren(t you living at 46 St . during the summer,
Regards to Barbara and to The Fourth.

Sincere}y,