Drosophila, many other labs throughout the world took up fruit fly genetics. Columbia became the center of an informal exchange network, through which promising mutant Drosophila strains were transferred from lab to lab; Drosophila became one of the first and for some time the most widely used, model organisms. Morgan's group remained highly productive, but Morgan largely withdrew from doing fly work and gave his lab members considerable freedom in designing and carrying oheir own experiments. He returned to embryology and worked to encourage the spread of genetics research to other organisms and the spread of mechanistic experimental approach (Enwicklungsmechanik) to all biological fields. After 1915, he also became a strong critic of the growing eugenics movement, which adopted genetic approaches in support of racist views of "improving" humanity. Morgan's fly-room at Columbia became world-famous, and he found it easy to attract funding and visiting academics. In 1927 after 25 years at Columbia, and nearing the age of retirement, he received an offer from George Ellery Hale to establish a school of biology in California. Caltech In 1928 Morgan joined the faculty of the California Institute of Technology where he remained until his retirement 14 years later in 1942. Morgan moved to California to head the Division of Biology at the California Institute of Technology in 1928. In establishing the biology division, Morgan wanted to distinguish his program from those offered by Johns Hopkins and Columbia, with research focused on genetics and evolution; experimental embryology; physiology; biophysics, and biochemistry. He was also instrumental in the establishment of the Marine Laboratory at Corona del Mar. He wanted to attract the best people to the Division at Caltech, so he took Bridges, Sturtevant, Jack Shultz and Albert Tyler from Columbia and took on Theodosius Dobzhansky as an international research fellow. More scientists came to work in the Division including George Beadle, Boris Ephrussi, Edward L. Tatum, Linus Pauling, Frits Went, Edward B. Lewis, and Sidney W. Byance with his reputation, Morgan held numerous prestigious positions in American science organizations. From 1927 to 1931 Morgan served as the President of the National Academy of Sciences; in 1930 he was the President of the American Association for the Advancement of Science; and in 1932 he chaired the Sixth International Congress of Genetics in Ithaca, New York. In 1933 Morgan was awarded the Nobel Prize in Physiology or Medicine; he had been nominated in 1919