Jennings, Herbert S. (Spencer)(1868–1947) protozoologist; born in Tonica, Ill. He held several teaching and research positions before completing his higher education, then studied physics and psychology in Germany (1896–97). There he began his controversial studies on stimulus-response behavior of unicellular organisms and lower invertebrates. He taught at Montana State Agricultural and Mechanical College (1897–98), moved to Dartmouth (1898–99), then became a professor at the University of Michigan (1900–03). He joined the University of Pennsylvania (1903–05), then relocated to Johns Hopkins (1906–38), where he made major contributions to studies of the genetics and sexual reproduction of protozoa. After retirement, he lectured and performed additional genetic research on paramecia at the University of California: Los Angeles (1939–46). His speeches and writings on the philosophy of biology were popular with both scientists and nonprofessionals.