September 27, 1950.

Dr, Marguerite Vogt,
Kerckhoff Labs.,
Caltech,

Pasadeha 4, Calif.
Dear Dr. Vogt:

Under separate cover, I am pheased to send 1177, which will, I hope,
meet your needs. Unfortunately, I do not have on hand a TLB,- Lac- vi vg?
W-1177 carries these markers except for V6", but you should have no trouble
selecting a v6" mitant from it. %~1177 also carries a number of other markers
which are not relevant to the ones mentioned.

I regret that 1 do not feel free to distribute Hfr without specific
instructions from Cavalli.

I am very pleased to hear that bacterial recombination is to be studied
in Dr, Delbruck's laboratory. Please feel tree to call on me for any further

information or other assistance. I shall shortly send you what reprints I can.
-Yours sincerely,

Joshua Lederberg,
Asscoiate Professor of Genetica.