Frank Rattray Lillie (June 27, 1870November 5, 1947) was an American zoologist and an early pioneer of the study of embryology. Born in Toronto, Ontario, Canada, Lillie moved to the United States in 1891 to study for a summer at the Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts. Lillie formed a lifelong association with the laboratory, eventually rising to become its director in 1908. His efforts developed the MBL into a full-time institution. Lillie was appointed an Assistant Professor at the University of Chicago in 1900. He was named Chairman of the Department of Zoology in 1910 and Dean of the Division of Biological Sciences in 1931. His research there was instrumental in the development of the field of embryology. He identified the influence of potassium on cell differentiation and elucidated the biological mechanisms behind free-martins. Lillie was instrumental in founding the Woods Hole Oceanographic Institution and served as its first president. He also served at times as the chairman of the National Academy of Sciences and the United States National Research Council. Biography Frank Rattray Lillie was born on June 27, 1870, in Toronto, Ontario, Canada. His father was a wholesale druggist and accountant. After attending a laboratory school as a youth, Lillie enrolled at the University of Toronto. Originally intending to study theology, Lillie came under the tutelage of Robert Ramsay Wright and Archibald Macallum, who influenced Lillie to study endocrinology and embryology. Lillie graduated in 1891 and moved to the United States. He accepted a summer position at the Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts, then became a fellow in zoology at Clark University, where he studied under Charles Otis Whitman. In 1892 he was lured by Whitman to the newly founded University of Chicago. In 1894 (at the age of 24) he received the degree of Doctor of Philosophy in Zoology summa cum laude. Between 1894-1899 he was instructor of zoology at University of Michigan. He married Frances Williams Crane, whom he met at MBL, June 29, 1895. Crane was the daughter of wealthy Chicago businessman Richard T. Crane. Between 1899–1900 he was Professor of Biology at Vassar College but in 1900 he was called back to Chicago as Assistant Professor of Zoology, where he would spend the next thirty years. In 1906, at the age of 36, he became Professor of Embryology. In 1910 he succeeded Whitman as Chairman of the Department