This is a diverse collection, including correspondence, drafts of letters, notes and notebooks (on biometric methods; tables and formulae; science, nature and method; coefficient and correlation; vitalism; Japanese language); commonplace book (1924); autobiography; and over one hundred folders of unpublished writings. The correspondence and other material covers a variety of topics, including biology, eugenics, evolution and natural selection, human heredity, paramecia, protozoa genetics, U.S. immigration policy. There is much on the Seventh International Congress of Zoology (1907); letters to his father and wives, and from students and colleagues on his seventy-fifth birthday, 1943 (1 v.); diplomas and certificates of membership; and photographs.

A botanist and historian of science at the University of Pennsylvania, Conway Zirkle published on the history of evolutionary thought and genetics, with a particular interest in the discipline as practiced in the Soviet Union. The Zirkle Papers consist of approximately one linear foot of materials accrued by Zirkle during research for his book on Lysenko-era biology in the Soviet Union, The Death of Science in Russia (1949). Among the miscellaneous materials in the collection are four volumes (0.5 linear feet) of pressed specimens of ferns and algae.