Letter to Pontecorvo from Joshua Lederberg discussing Pontecorvo's paper given recently in Bristol [on diploids and Aspergillus]

Letter sent to Pontecorvo from Professor Joshua Lederberg thanking him for sending a reprint on auxanography and discussing his work on recombination

Letter sent to Pontecorvo from Professor Joshua Lederberg commenting on a point about the "absence of inositolless mutants among bacteria", which Pontecorvo discussed in his paper for the Biochemical Society Symposium

Correspondence between Pontecorvo and Professor Joshua Lederberg concerning Dr Joseph Alan Roper's Rockefeller fellowship and 1 year trip to the United States

Photograph of attendees of the UNESCO Conference on Patterns of Biological Organization at the Institute of Animal Genetics, Edinburgh, 6-10 September 1957, and of friends and colleagues at the CIBA Foundation Symposium, London 27-29 March 1957

Copies of thank you letters sent from Pontecorvo to colleagues and friends met during his recent trip to Harvard University

Photographs of Pontecorvo with friends and colleagues in Cold Spring Harbor 1956, and at a meeting about Recombination, c1960

Correspondence chiefly about research topics