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April 24, 1958

Dear Dave:

It is good to hear from you, I don't kmew whet to advise on general
procedure in looking for assistants except to let your friends Imov and to
advertise at places like CSi, In fact, I just had the enclosed letter from
a “ry. Bullas who might interest you. His main interest has been in Salmonella
phages and serology but he would Ifke to broaden his training ."le see ed sound
enough, not worldeshaking, but eaper to work. [le is loolcing for the pogsibility
of working for a Ph.D,, or for a more temporary assiatantshin. I don't think
you are likely te cet much more useful information than this fron further in-
quiries; if you really don't have any more obvious candidate, I don't see
how you'd lose anything, by takinc him on, He was 9 very pleasant chap and
at least moderately intellizent, thourh not too familiar with contemporary
work,

Luce Cavalli is here for a couple of monthe and we have been going over
the various experiments on timed interruption. I only just realized how
one could ret such precise information on timing by extrapdlating to the
x axis, and the kinetics of the ~edel ie just becoming clear to us, We are
trying to tidy up some of the second order muantitative effects, on the one
hand, «nd to find out whether the process that ta interruptac ie obromozome
tranefer or progressive pairing on the other. (One can stil! imagine that the
nuclear tr.nsfer occurs in a few minutes. but that pairing rrorreases from
one point down the chromosome; markers in unpaired serments are lost by their
linkage to the terminal deletion, This would also necessitate that ayrotie
incuction of prolambda also needs pairing.) I really don't kmov what te think
of these alternatives, and am having sone trouble designine really critical
experinente to chocee between then, Améne other thinsa we cro looskins for ways
of serarating the vairs without interruptins the padrine, so far without
conspicuous succeas (as you and Pranceig would doubtless predict). Protoplasts
are mafing beautifully, and protonlast 6 x rod ¢ five » very nice method of
interruption by lysis in water. But of course, mocerately virorous sprendinc
on asar does very vell too! We have succeeding in diluting mixtures in broth
gently enouch not to interrupt,
There is one method that I hoped you might be the one to tackle: to Zo
back to your old experiments on Po transfer, But the way to handle it is by
stars, of course, I would mate protrlast 5% * x rod 99 and lyse at various times,
plating for stars, If there ie gradual transfer of DXA this should show up very well
in the distribution of sizes 7 stars, You would probebly have some backrround
of unlysed Hfr* (+ 10°? or 107 ) which would show as full sized sters throughout,
and of course there would be small stuff that wouldn't count et all. How about 4+?
The P39 experiments so far measure the amount} ineorrorated (by its suicidal effect)
not the amount transferred.,

We had e symposium here keet—wee a couple of weeks apo, and we were down to
Gatlinburg just before then. We still haven't recovered, and the pressure of time
has been unusually harassing this season, Not much else new heret we made a bid
to get Al Hershey for Genetics and Chemistry, mmxfmx but it didn't pan out,

Wait till you get your 4' blizzard in mid-May!

All the best to Linda and Co,-~ when might you be travelling through this vay?
We'll be here from now on t411 late July, when we're scheduled for the Royaunont-
Stookholg-Montreal cycle,

Yours,

f

P,8. Another perfenel possibility of a different sort just occurred to me; she
explains herself in the second enclosed thermofax, I have already mentioned her
to Larry Morss, ht con't ‘mow whether he nas responded in any way. Mer stull on

conjugation in Spktrillume looks interesténg, and they are fascinating bugs in any
case,

toes Cele 2 bb