25 April 1952.

Dr. Ed Garber,

Dept. Hacteriology,

Naval Blological Laboratory,
Naval Supply Center,

Oakland 4, California.

Dear Fd:

First, I'd like to say that I would prefer not to discuss any
uncleared information except in the course of arfanmal consultaticn.
It get's to be too mich of a mental burden to sort things out. However,
I'll be happy to talk over (i.e. via letter} anything which has beer
cleared for oublic discussion.

The mitation rates you give are the lowest I've ever seen for any
measurable rate; you must be working with incredible densities of bac-
teria; this makes me wonder whether thare's any chance of an artefact
coming in there. Do you get full recovery of small, known numbers cof
S* celle aided to 3° populations?

DT hope you'll enjoy your summar at CSH. We'll be there for the
sympestian, but that will be over long before the course starts.

Sincerely ycurs,

Joshua Lederberg.

P.S. Why not use Lea and Coulson's methods for measuring mutation rate

from the median nuaber of mutants (J. Genetics 49:264- '49)? Also,
evidence from *, cold heterozygotes showe that S*° is dominant to s*,

You should be able to verify the diploid nature of the gigas forms

by measuring the mtatiéa rate from 3° to 3. We got absolutely nothing

in FE. coli with camphor. On the other hand, T have been surprised to

find myself utterly convined of the "Leforms" and their role as "filtrable"
bacteria from work one of my students is @oing on Sal. monella.

JL