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Dear Bill:

Alan Richter (a student here) let drop a reference to a conver-
sation with you to the effect that your fry has been quite stable

while Hfrg has been unstableg giving F+.

Now the situation here has been just the reverse: except for the
single historical case here, HET, has been akemuk absolutely stable

(except for some off F- after UV or motility selections) and has not
since given any F+ at all. But luca says his old culture man now
lost was quite unstable. So the existing cultures now are:

Madison Lomdon ?

Hfroavalli stable unstable

Py v. unstable stable
ayes

The instability is one point that had blinded me to the now very
apparent differemce in behavior of the two Hfr's; with the cultures I
worked with preliminarily, I did not get a convincing Hfr reaction

with , with any regularity. Anyhow it's obvious there should be

a re-collation: I will be very happy to send yop anything that would
interest you now; in turn may I ask you the favor of a) confirming
the statements above, and b) if these are correct, sending me the
representative cultures. If you have them, esrecially Afr: as
«s° (rather than u’s® Tht or MS" as I have had \it)’ this would be
especially convenient. he

4

Yours s incerely,;

Joshua Lederberg