The geneticist Milislav Demerec emigrated from Yugloslavia in 1919, spending nearly his entire career in the Department of Genetics at Cold Spring Harbor Laboratory. Working initially on the genetics of maize and later on Drosophila virilis, his research interests included radiation and chemical mutagenesis, and during the Second World War, penicillin and the genetics of antibiotic resistance. Demerec served as head of the laboratory at Cold Spring Harbor from 1941 until 1960. The Demerec collection contains the extant professional papers of Milislav Demerec, dating primarily from the time of his arrival at Cold Spring Harbor until his retirement. In addition to his correspondence with colleagues, the collection includes interesting material on the administration of Cold Spring Harbor laboratory during the 1940s and 1950s, data and research notes, material relating to professional organizations (e.g. Genetics Society of America, American Society of Naturalists), a lengthy series of lectures given by Demerec, and a large number of photographs pertaining to Demerec's research, but also to his colleagues and Cold Spring Harbor itself. There is also a Register of visitors to the laboratory (1927-1945) and a Milislav Demerec reprint list.

Ernst Wolfgang Caspari was an important contributor to behavior and developmental genetics, working primarily on the mealmoth Ephestia. Trained in Alfred Kuhn's laboratory at the University of Göttingen (1933-1935), Caspari was forced from his position by the Nazis in 1933, escaping to the United States five years later. As a professor of biology at Lafayette College, Wesleyan University, and the University of Rochester, Caspari continued his research on Ephestia, mouse genetics, and behavior genetics until his retirement in 1975. The Caspari Papers includes correspondence, papers, grant reports, and lectures relating to Caspari's genetic research dating primarily from the period after his departure from Germany. In addition to substantial material on behavior genetics and human evolution, the collection includes correspondence relating to Caspari's editorial work for Advances in Genetics, and his involvement with the American Institute of Biological Sciences, the Center for Advanced Study in the Behavioral Sciences, Cold Spring Harbor Laboratory, Fifth Banff Conference on Theoretical Psychology, Genetics Society of America, International Conference on the Unity of Science, Social Science Research Council, Committee on Genetics and Behavior, and the U.S. Atomic Energy Commission.