12. x1.52

liy dear Bill, .
Thank you for your letter of Oct. 27,1952. The fly-wheel
cars have come,and the children have been delighted with them. As they
are a novelty here,also adults have tazen a considerable interest

in them, Thank you very :weh for them !

I was very pleased to heez that you are working at
understunding the genetics of K~-l23;it took me a long time to get
deeply enough into it,I mean into the understandzble portion of it.
Re F+,i have been often thinxing in terms of a centrome:e regarding
it. dham Some time ago (Iat@ in september) had come to the conclu-
sion that f+ was the centromere of a twoearmed chromosome,and that
one or the other of the two arms is usually lost,as if F+ were a
sort of weak centromere which could not carry both aras.I used to
prefer this,to Watsons's interpretation for a time,ané am even now
slightly biised for it. Some new data do not fit watson's interpre=
tation. "hémx may well be due to other complications,anyhow. 7 have not
reuched a definite conclusion about dim's theory,however.The most in-
portant xperiments have still to be done.Tf it is right, however, the
chromosome lost may well be different in different instances,2s my
data sugsest. Also your suggestion as to Hfr is quite good. We have
however to account for xkmxal the loss of Hfr in ali,or almost all
recombinants, Lecently again 7 tested a number of offsrping from FTx
x Hfr;they were all Pe, If the theory T have in mind about FY is cor
reet,half of this offspring should be transducibie fo F+,and half
not tranduscible{i.e.Fr),but it will take me some time to test it.

< have given up the idea of the | symbol.I did not ;
realise the possible confusion with phages still I agree that F+ may
in the end prove to be phage.

There is not mich new to report from wy laboratory.I
shall be greatly interested to know of your results,
Yours,