November 8, 1955

Dr. John R. Raper
Biological Laboratories
Harvard University
Canbridge 38, Mass.

Dear John:

I happ I haven't waited too long to answer your letter of October 13,
but my own good inéentions have been punctuated with trips, etc. , etd.

Your course sounds like an exciting (and laborious) prospect, and I will
be glad to help any way that I can. I think the Wollman—Jacob experiment
would be rather too strenuous for a graduate student group-- if you do want
to do it, you should perhaps get their own strains to be sure it works as
they report. Insteai, I would have thought that a thorough review of the
compatibility altuation would be more appropriate for the aims and background
of a course like yours. You can have the students set up the basie tests for
compatibility (F+, F~); demonstrate infective conversion of F- to P+; the
aeration phenocopy; the effect of F polarity on segregation ratios; ,without
tremetidous difficulties. The basic materials are described in the enclosure ;
and we will send you the relevant cultures in a reaso nably short tins.

We do stumble into Ken occasipnally —- we're next door neighbors in the
new Bact. building, at least for two or three months while they are remodelling
our old space in Genetics:: which is one reason (agong others) for delays.

Yours sincerely,

Joshua Lederberg