September 11, 1955

Dear Dr. Leifson:

I spent some time this weekend on some cell pedigrees with your
cultures, particularly with Hl, H42, H47 and H300. The latter three were,
for technical reseans, not the most favorable for pedigree atudies: H1
worked very cleanly. A couple of dozen cells were followed for from
one to three fissicns,.

Onee the cells were growing rapidly again, about lf the fissions
gave one t, ane ~ pair (+ = immediately motile; - = initially nonmotile,
becoming motile before the next fission). This is not consistent enough
to be worth following up in great detail, and there does not seem to be
a definite pattern. So probably, it is only a matter of the rehtive rates
of flagellum formation and cell dividion. Ons pedigree was provocative:

+o +
Se

But the suggested rule, that + gives +,-; - gives +,+ was not consistently
followed in other fissions.*#There still may be som such pattern, but it
would be too much of a digression for me to go into it just yet. If you should
run into other cultures in which bipolar cells, ar bipolar cell pairs, are
strikingly absent, I would appreciate your bringing them to my attention for
possible future triele. Thank you for your courtesy thus far.

Yours sincerely,

7

VS sy
4BG hua dedestierg-—-1
// Professor of Genetics

Hkfxiixx *This might be interpreted ast + mearky "old flagellum"; — means a
newly formed one, or, in =m a sense, that the flagellag for two cells are
formed every other division.