Typescript draft lecture notes titled, 'A genetic hypothesis on the origin of epidemic strains of pathogenic organisms'

Two drafts with corrections and accompanying letters from Alfred Hershey of Washington University and Max Delbrück of Vanderbilt University in Nashville, offering feedback on Pontecorvo's paper and his ideas on recombination.

German born Delbrück was a pioneer of modern molecular genetics. He moved from Berlin to the United States and spent most of his career working in the Biology Division at The California Institute of Technology (Caltech), although he did spend six years at Vanderbilt University in Nashville in the 1940s. Alfred Hershey spent his career working in the Department of Bacteriology at Washingon University in St Louis and the Carnegie Institution of Washington's Department of Genetics at Cold Spring Harbor.

In 1942 Delbrück and Salvador Luria of Indiana University demonstrated that bacterial resistance to virus infection is caused by random mutation and not adaptive change. This became known as the Luria-Delbrück experiment. Delbrück, Luria and Hershey were later awarded the Nobel Prize in Physiology or Medicine in 1969 for their discovery on the replication of viruses and their genetic structure.