TECHNISCHE HOGESCHOOL LABORATORIUM VOOR DELFT, February 13th, 1953. MICROBIOLOGIE NUUWE EAAN 5 SESTEL: Dr. Ja@hua Lederberg, Department of Genetics, University of Wisconsin, Madison 6, Wisconsin. (U.S.A.) Dear Dr. Lederberg, I am in receipt of the reprints of your recent papers which you were so kind to send to me. May I assure you that I have much appreciated your kindness. I have attempted to follow your interesting work, and I congratulate you with the fine results obtained. But, some of your recent publications had until now escaped my attention, and I am very glad to have them as rey prints. Yours sincerely, a (A.J.Kluyver)