Jujy 16, 1953
Dear Luca:

I have finally gotten round to taking some pictures of the "Verbindungsbrticke"
I mentioned having seen some time ago. These are all from a single slide of Hfr x F~
(W~1695 x W-1177), impression from nutrient agar; oamic vapor; HCL-Giemsa, mounted
in Abopon. The slide ia over a year old now— I can only be thankful it has lasted
so long. I have no idea of the significance of these things, and it will take some
difficult experiments to find out. This slide is so far the most dramatic demonstration
of the objects; I have seen them in others (of Hfr x F~), but mich less conspicuously
as 4 rule, and until a more consistent technique is worked out cannot be sure of any
correlation with mating.

The American Bacteriologists are meeting in San Franelscco. You will be pleased
to learn that Genetics 1s now respectable: I have been asked to give the Eli Lilly
Award lecturs@fig for this meeting, and as the trip will be somewhat of a vacation,
we are looking forward to it. We will leave here about July 27; until 4ugust 15, we
will beat be reached care of Roger Stanier, Bacterlology Dept., U. of Calif., Berkeley
Ay California. Sincerely

?

Josma Lederberg

P.S. I have, of course, no objection to your discussing these photos with
whomever you please, at your om discretion. But the phctures mist speak
for themselves: I have no interpretation of then so far. I hopa we will be
able to pursue this problem without the pressure of any competition, which
might lead us to hasty conmitments— this has been the main reason for my
wish to reserve the Hfr, and I hope this policy can be continued without
embhrrassment to yourself. {I do not believe that Hayes' culture 1g comparable
to Hfr-- have you seen his C.S.H. ms.? We find the same ratio of By* 3 B,-
in Hfr x F~ as in F+ x F~, while Hayes claims that his "Hfr" can trahamit
fonly the Lac-I-T chromosome"with high effidé¢ciency, so that By,~ is very
greatly in excess of By)+ im his crosses. ]

JT