Jamary 15, 1951.

Dr. F. 0. Holmes,

Rockefeller Institute for Medical Research,
éSth Street and York Avenue,

New York 21, N.Y.

Dear Dr. Holmes:

First, let mse tell you how mech I appreciate the cordiality of
your reply tc my hasty letter to Dr. Braed concerning the noxnclature
of Phagua testacilis.

It was the phrase “when heated in spores” which threw me off, because
I tnerefcre carelsssly connected this description with Dr. Cowles! better
known work on the heat resistance of lysogenic phage in Bacillus subtilis
(J. Bact., 22:119-123.) I hupe that both dr. Ereed and yourself will ac-
cept sy apoiogles for this careless confusion of references, a rather in-
auspicious Introduction to a critique cf nomenclature.

The phage reported by Coales in his 1922 paper resembles the Aaxt des-
cribed °. indomltus. In this organism, one finds that heating the phage
in spores does not inactivate the lysogenic notentislity, whereas heating
in the presence cf epores does so, This, this exveriment has been used
ifaliaciously, 1 think] to support the idea of intrinsic origin. On the
other hand, the finding, in B. megatherium with F. testabilie, that the
extrinsic phage is destroyed by heating seams to have little bearing on the
question of intrinsic origin. Cowles does indeed remark that his spores
were heated tc remove phage, but this follows imnediately upon a statement
that filtrates-of the bacterium showed no phage (unless, of ceurse, the
culture was experimentally infectsd) .

Te I may summarize the source of ay confusion, I eculd not follow the
rationale of the attestation to which P. testabilis refers (C.,1920). On
the other hand, a similar experiment (1922) with the opposite result, has
been an imprtant verification of the principle that a phage, introduced
from without, eculd show the behaviar argued for intrinsic origin, was of
very considerable importance in clarifying this question. May I therefore
withdraw ay complaint to Dr. Bresd that a false conclusicg was drawn from
false ptaglaeggnwith the rather weak excuse that I was referring to another
syllogism.

Sincerely,

Joshua Lederberg
Assciate Professor of Genetica