INDIANA UNIVERSITY
BLOOMINGTON, INDIANA

DEPARTMENT OF ZOOLOGY

March 31, 1947

Mr. Joshua Lederberg

Osborn Botanical Laboratory
Yale University

New Haven, Connecticut

Dear Mr, Lederberg:

Thanks for your kind letter calling my attention to the passage on
Euglena mesnili in Lwoff's book, I have had the book for sometime and while I
have not read it thoroughly, the subject of this particular passage was dis=
cussed with Lwoff when he visited our laboratory last Summer. Lwoff was quite
aware of the resemblance of chloroplast behavior here to the behavior of our
cytoplasmic factors, and that is why he called it to our attention. I quite
agree. The whole general question will be discussed fully in papers now in
preparation in our laboratory, particularly Preer's dissertation which I am
to see the first draft of tomorrow. The reference you want is Lwoff, A et
H. Dusi (1935¢): La suppression expérimentale des chloroplastes chez Euglena
mesnili. C. &. Soc. Biol. 119, 1092.

It seems to me that tae similarity between the behavior of our
cytoplasmic factors, aaa behavior of plastids,and the behavior of intracellular
symbionts is inevitable, I have recently thought the matter through as well
as I can from the point of view of what the possible mod@s of behavior of these
three classes of objects could be. As a result of this reflection, I am con-
vinced that it is impossible to reach a legitimate conclusion as to whether, any
particular substance is a symbiont or a normal cellular constituent on the, basis

of its general behavior in the cell, Awa Of couaas 10 soaewhabd, {ke corcheacen danced by SnslongNor N%&

4 ,
Since I saw you last, we nagseaeen extending our study of cytoplasmic
factors to other characters than the character and have piled up an
impressive mass of evidence, confirming my earlier conclusion that this is the
normal and regular method of inheritance for all characters in these varieties
of Paramecium aurelia. It is extremely easy to demonstrate the cytoplasmic
factor basis for each character and extremely difficult to find any genic con=
trol whatever. Our evidence indicates that our various races of variety 4 are
genically alike with respect to most of the characters we are studying and
that they differ only in cytoplasmic factors for these characters,

I should be very glad to hear further about the evidence for your
single linkage group in coli, This is great stuff.

With best regards and much thanks for your good letter,

Cordially yours,

T. K. Sonneborn

TMS set