The Austrian biologist Paul Kammerer was an outspoken proponent of the theory of inheritance of acquired characteristics (Lamarckism) during the time in which Mendelian theory was becoming deeply entrenched in biology. His major research efforts, straddling the First World War, centered on experiments performed on salamanders and on the midwife toad, and seemed to provide empirical support for a Lamarckian mechanism in evolution. He also developed a monistic "law of seriality," in which he attempted to explain coincidence as the product of a higher order natural law. A Socialist, Kammerer was widely regarded as a brilliant scientist, but for scientific, personal, and political reasons, he engendered as much antagonism as support, preventing him from ever obtaining a regular university appointment. His career ended tragically in allegations of fraud, followed by his suicide. The Kammerer Papers is comprised of photocopies of materials that document the brief, but controversial career of a non-Darwinian evolutionary biologist. The bulk of the collection consists of photocopies of articles by Kammerer, often from obscure newspapers or periodicals, along with a small number of letters to his friend Hugo Iltis, the geneticist and biographer of Mendel. Nearly all of these pertain to the Kammerer's experiments with amphibians to test Lamarckian inheritance or to his other biological theories. The collection also includes a small number of items dating from after Kammerer's death, but relating to his life and work, including two letters from his former supervisor Hans Przibram, a letter from Hugh Iltis (Hugo's son) to Arthur Koestler and the reply, and a brief biographical reminiscence of Kammerer written by Hugo Iltis.

A modest Midwesterner who became one of the most influential geneticists of the first half of the 20th century, William E. Castle spent his career at Harvard and the University of California working on patterns of inheritance in mice, horses, and a variety of other mammalian taxa. An early proponent of Mendelian theory, Castle was director of the Bussey Institution at Harvard for almost thirty years, helping to train a number of important geneticists. The Castle Papers contain one linear foot of correspondence dating primarily from the period after Castle's "retirement" to Berkeley in 1936 until his death in 1962, dealing almost exclusively with his research on horse breeding and the inheritance of coat coloration in horses. Castle's correspondence with his former student L. C. Dunn is an exception, focusing on mouse genetics and ranging to a variety of topics from the conduct of scientific research during the Second World War to Castle's interests in the early history of genetics.