June 29, 1953
Dear Dr. Lederberg,
Please accept my grateful thanks for the reprint of your paper "bell genetics and hereditary symbiosis" and two other reprints which I received yesterday.  After the first reading I admire your thorough review and your views will be of the greatest value for my further investigations.
As you may have seen from my paper I have only done the first steps in the new field of the genetics of [...].  This paper contains also my finding till the winter 1952/53.  In the meantime I could get some more new incompatible strains so that I have now at least five, perhaps six groups of types as regards the crossability in culture.  A second paper on these findings has gone to press and I will send a reprint as soon as possible.  I would appreciate it very much if you would put my name also on your mailing list.
Sincerely yours
H. Laven