July 15, 1946.

Dear Kim:

  How'8 interning- have they sapped you dry yet? what have you heard

from the Navy aboUt a period of service when you're through?  They jsut
sent m an HP Ensignship a couple of weeks z&o. However I'm staying up here

another year with a leave of absence.

  The Cold Spring Harbour Syntpoaiumthis mer on Heredity and Variation

in Miclw>rganisms has just closed. Included was a paper by Lederberg and
Tatum on 'Novel Genotypes in Mixed Cultures of Biochemical Mutanta of Sacterha+

The evidence is @a conclusive, although perhaps meagre in quantity, for

a recombination process in E. coli: we get out 4l4 types from mixtures

of double or even t&h& biochemical mutants, and we can shornr segregation
for phage resistance in these wilds (prototropha). Also we have isolated
E (1) new recombinant of a recessive type: from biotin-&Lanine-cystine-l&es

and threonine-proline-less a biotin-prol3neless. .@etre looki& for more

obviously.  'lhere was quite a fuss after the paper was presented- I got

Into an unfortunate argument with Lwoff, but everything was smoothed out

eventually. DelbrUck aunnariged 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 tith you but every
tine I called you were out`2 &en(t you living at k6 St. during the summer.

Regards to Barbara and to The Fourth.

SincereJy,

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