January 13, 1953

Dr. U. N. Lanham
Department of Zoology
University of Michigan
Ann Arbor, Mich.

Dear Dr. Lanhand
Thank you for your letter of January 9.

I hope my review suggested no pretensions on my part of expert
knowledge of insect symbioses, Few geneticists are so much as aware
of the existence of these things, and it was my hope to present then
as they seemed to be in their genetic aspects. While we should be care~
ful to sort out the various phenomena, I note that you will accept at
least the rickettsia as endosymbionts subject to transovarial trans—
mission, and I assume that you will admit at least the occasional intra~
cellular habitat of some of the yeast—like forms, notwithskanding these
seem usually to be tranamisted on the eggesurface, rather than inside.
Without wishing to gloss over important distinctions, however, I suggest
that from some points of view the most important fact is that the symbionts
are regularly connected with the reproduction of their hosts. To put the
matter another way, differences due to symbionts would be very likely to
show up in croas-breeding tests as if they were due to cytoplasmic or
matamnally inherited factors,

Your comment on Pseudococcus brevipes waa especially interesting.
I can only hops that a more extenhive application of genetic and microbio-
logical approaches to these problems will settle then fihally.

Although I am not working in insect symbioses myself, I should be

indebted to you if you would keep me in touch with your future work via
reprints of your publications.

Yours sincerely, ae

Joshua Lederberg
Associate Professor of Genetics