April 22, 1958

Dr. Hideo Kikkawa
Medical School, Osaka University
33 Joancho, Kitaku, Usaka

Japan

Dear Dr. Kokkawa:

Please forgive me for not having written sooner to acknowledge the safe
arrival of Hirota-san and your message which accompanied him. He is now
wall settled in the laboratory. Even before he could comminicate easily in
English, which is improving, he was most eager to embark on his experimental
program, which he has been doing very successfully almost since the day of
his arrival, He is now working on a more detailed kinetic analysis of the
removal of F by acridine orange in order to secure more decisive evidence
that it is an induction, not a selection of spontaneous mutants. The latter
is still a possibility but a rather remote one. In any event this has been
a most remarkable and useful discovery. As Hfr mutants are not rendered self-
incompatible by the dye, except through the intermediation of some Hfr -> Ft
reversions in some strains, this work adds to the evidence for the cytoplasmic
nature of F, the same factor finding a chromosomal locus in the case of the
various Hfr mutants.

As I already indicated Hirota is muking a rapid and happy adjustment to
conditions here, As you would have predicted everyone is very fond of him
and I am more than delighted to have him as a student in my laboratory. Please
accept my gratitude for your good offices in arranging this.

Tetsuo Iino-haksh has just completed his graduate studies and is en route
back to Misima via London (for a few months with Dr. Stocker) and the Stock-
holm Microbiology Congress. He is another research geneticist of whom
Japan may be justly proud.

Yours sincerely,

Joshua Lederberg
, Professor of Metical Genetics
JL/ew