Correspondence between Pontecorvo and John L Yuill concerning Pontecorvo's research using Aspergillus nidulans for the study of heterokaryosis and his production of x-ray mutants from Aspergillus nidulans culture

Correspondence between Pontecorvo and John L Yuill concerning Pontecorvo's research on the production of diploids

Correspondence between Pontecorvo and John L Yuill concerning an update on Pontecorvo's research using strains of Aspergillus niger sent to him by Yuill

Correspondence between Pontecorvo and John L Yuill concerning techniques for the isolation of nutritional mutants

Correspondence between Pontecorvo and John L Yuill concerning an update on Pontecorvo's patent application

Bundle of correspondence between Pontecorvo and John L Yuill concerning Pontecorvo's request for two coloured mutant strains of Aspergillus niger in order to experiment with obtaining heterozygous diploids using "corssing" technique

Correspondence between Pontecorvo and John L Yuill concerning research on heterokaryons and experiments with Aspergillus niger colour mutants

Correspondence between Pontecorvo and John L Yuill concerning research on the production of diploids from balanced heterokaryons arising between mutants of Aspergillus niger

Correspondence between Pontecorvo and John L Yuill concerning research on heterokaryons

Letters sent to Pontecorvo from John L Yuill asking for samples of Pontecorovo's Penicillium notatum and Aspergillus oryzae cultures and their x-ray mutants