chromosome rearrangements using polytene chromosomes. (Polytene chromosomes are large aggregations of actual chromosomes which, once appropriately stained, facilitate the discovery of chromosome rearrangements through an ordinary light microscope. Polytene chromosomes are mostly found in the salivary glands of some species.) In his studies of pre-mating isolation, Crow was one of the first to study genetic reinforcement, and also observed that species occurring together were sexually isolated, while those living apart were not. A great influence on Crow at the time was W.S. Stone, who encouraged him to learn more mathematics, while he himself knew none. Later on, Crow admitted to struggling with some of the advanced maths and physics courses he took as a result, but also said they had been rewarding. Dartmouth College and the war Crow graduated with his PhD in 1941 and moved to Dartmouth College just prior to the American entry into World War II, where he remained until 1948. The original plan had been to get a postdoctoral fellowship to work with Sewall Wright at the University of Chicago, but this proved difficult just at the start of the war. His appointment in Dartmouth was to teach genetics and general zoology, but as faculty were drafted off into military endeavors, Crow took on an increasing number of courses. Crow particularly delighted in being able to teach embryology and comparative anatomy. When it seemed likely that he himself would be drafted, Crow took a course in navigation, at which, owing to his mathematical training, he proved so adept that he was asked to teach it. As parasitology became relevant to the war (as it did on the opposing front, where Willi Hennig was active in this area), he was asked to also teach parasitology and haematology. Not long after, he was also teaching statistics. It may be that, having to teach many hours each day, Crow discovered his love for teaching at this point. He later recounted that there were several students all of whose courses were taught by him. He, like many of his colleagues of the era, had college-time involvement with pacifist groups that had communist leanings. During WWII, he tried to enlist, but was deferred until the end due to his teaching commitments. Race and IQ controversy Crow wrote "Genetic Theories and Influences: Comments on the Value of Diversity," an article in the Harvard Educational Review reprinted in the review's reprint series responding