NEW YORK STATE COLLEGE OF AGRICULTURE CORNELL UNIVERSITY ITHACA, NEW YORK LABORATORY OF BACTERIOLOGY July 24, 1953 Dr. Joshua Lederberg Department of Genetics University of Wisconsin Madison 6, Wisconsin Dear Josh: Thank you for your recent letter. With respect to the photographs--"The Lord only knows." The only thing I can suggest would be attempting to observe the living cells and follow their behavior, I am going to San Francisco, and I shall see you there. JI think I am staying at the Sir Francis Drake Hotel, but I am not positive. At any rate, I will look you up. We aren't working on recombination in Azo- tobacter. You think one should? Looking forward to seeing you in San Fran- cisco, I am Very truly yours, M. R. Zelle Professor of Bacteriology