A
ane

Dear Bill:

September 16, 1954

I have to ask your apologies for both the belatedness and immateriality
of this reply to yours of the 4th August. I was fortunately able to take a
sort of holiday for most of the summer, and while your letter was eventually
forwarded to me, this has been my first opportunity. Unfortunately, I still
do not have the time for ff as deliberate an answer as I ought to give, but
yeu will unmerstand it if I tell you that I have to prepare my lectures for
this year's course, handle students, complete the moving into a new house
(yes again, but now for the first tim our own property) amd dispose of the
usual odds and ends of getting back to wrk. We haw also the pleasant occu-
pation of entertaining the Cawallis, who arrived just a few days ago.

If I answer your detailed questions at all, it is with some risk of error 3
as they concern work in which I am presently concerned, and on which I am not
in a position to quote final conclusions. I think I can say that we have isolated
Hfr recombinants from single-celled zygotes, but that rectiproeal redombinants
are, at least usually, lacking. These finiings are subject to revision with
more extensive study, and I should not wish them to be quoted yet. So far, they
are entirely consistent with the viewpoint embodied in the paper by Nelson
and myself that appeared in the PNAS ea lier this year.

Jacob was kind emough to seni a copy of his ms.His observations are extremely
interesting: I would interpret them as inlicating that the "cytoplasmic state”
of the sensitive parent results in the indtiction of a proportion of gametically
introduced lambda-prophages. But like yousself, I do not quite see what thts
has to do with elimination or segregation ratios. In our experience these are
not appreciably influenced by the substitution of Lp§ for Lp? in either or both
parents, though the quantitative yield of viable zygotes may very well be affected.
If, as we believe, all the gametes are complete, the "erotic induction" should have
no effect on segregation if a raniom sample of the zygotes are induced, and there
is so far no evidence to the contrary.

In my earlier letters, I hai asked you for your results on the nature of B,
becaise I had the impression from our conversations in Madison a year ago
that this was to be the object of your work at Caltech. I was sorry to learn nat
otherwise; but am gratified to learn you are going back tomit. Unfortunately,
like yourself, I am somewhat at a loss to suggest just what to do, The only approach
we visualize at the present is a closer study of diverse strains, whose compatibility
(ani I hope elimination) systems may differ slightly from that of K-12.

In an earlier letter, you mentioned some very interesting results with 13, which
promptly interrupted fertility of Hfr. Without your explicit approval, I did not
feel that I could quote them publicay, despite their important bearing on the
nature of the gamete. Have you done more with this? Do you intend to publish
it soon? In 1946-47, I had had a similar resukt in a few experiments with Tl,
but did not pursue this line as there was not then any conflict of interpreta
tions for which this would have been relevant. Since I am not sure now of the
F status of the cultures used for that particular experiment, it may be of no
particular force how either, and I mention it only as the basis for being in
no way surprised at the outcome of your experiment. In due course, I am K¢Ppin
planning to try to ¢Xtdd/rh extend the design of your original S* experiment
to some other undoubted sexual systems (yeast or Chlamydomonas). I shall be
astonished if toxins are not found here also that will separate vegetative
from sexual vitality: thete use might be in diffenentiating the cytoplasmic

contributions of the two patents.
Yours sincerely,