PUBLIC HEALTH LABORATORY SERVICE (Directed by the Medical Research Councilfor the Ministry of Health) 7041 Telephone : COLINDALE m Telegrams : DEFENDER Central Enteric Reference Laboratory COLINDALE AVENUE LCINDON, N.W.9 26th November, 1952. Dear Professor Lederberg, I am enclosing herewith a reprint of a recent letter to Nature by Dr. Felix and myself'. Many thanks for the last batch of reprints you sent me. I should be very grateful if you would continue to keep me abreast of whatever you publish in bacterial genetics. I hear that Spicer is enjoying himself in your laboratory. Please give him my best wishes. Vith kind regards, Yours sincerely, E. S. Anderson Professor J. Lederberg, Department of Genetics, University of Wisconsin, Madison, Wisconsin, U.S.A.