August 3, 1946.
Dear Dr. Luria,

The two available mutants in B/r have been mailed to you, and you
should have them in your hands promply. I hope they can be useful to
you. It occurs to me that the biochemical requirement could be used
as a marker to determine whet her those few strains reported by Demerec
and Fano which were resistant to each Phage are contaminants, or mitants,
I shall be particularly interested in the results of your (or Adams')
growth factor experiments. Let me know if there are any specific mum
growth factor requirements that you are interested in, and I shall look
out for them and send you the appropriate strains. So far, only the
two strains I sent have been identified as mutants of H/r. There are
some others not yet identified.

We have been working for some time with single resistant mutants;
thank you for your kind offer,nevertheless. However, we feel that our
experience is inadequate to cope properly with the probhem of complex
resistance patteras, and we hope thet you will continue to look for
it in K-12, If you find it there, I am sure we can work out some means
of handling the genetic analysis using phages and biccherical mutants
together. Meamtime, we have been accumulating sore data on the occurrence
of recombination types, and have ‘several instances now of biochemical
recombinations (B~P-, B-l-, B-P- from Be... @x Tale, or X P=T=..)
and of biochenical-resistance recombinations, e.g. B-/1 from B=..X
{T-P~/1 , and from a similar cross, T= (ausc.) ‘'e have only now begun to
use more than one virus, however,

Do you expect to be in N+Y.C. at any time in the next three weeks; 1 .
+
ite ;

would like to arrange an appointment, anywhere inwN.y, fy Lr’