This collection includes correspondence, manuscripts (lectures and articles), research grant material, research data, and participation in organizations, such as, the American Society of Naturalists (President, 1968), Genetics Society of America (President, 1963), and the National Research Council. Of particular note, are the detailed data related to Drosophila eye pigment, and human chromosomes.

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and correlation; vitalism; Japanese language); commonplace book (1924); autobiography; and over one hundred folders of unpublished writings.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.