May 6, 1944
Dear Sonneborn, could you let me have the reference to [...] obituary notice in which he mentions [...] results on mutation induced by antisera?  I could not find it in the Biol. Bull.
Hope you returned without mishap.  I am not steeped in literature on physiol. genetics, coming to it next week in the talk at the Med. School.  Wish I could ask you many questions.  I think it is a depressing subject, as yet.  Luria is coming today.  Maybe he will cheer me up.
Discovered that I left my hat at your cousins.  Hope to retrieve it when we take Luria there.
Had another note from Ephrussi.  Says he is now really going to leave for England soon.
Sincerely
M. Delbruck