The American zoologist and geneticist Thomas Hunt Morgan (1866-1945) established the theory of the gene which helped clarify the process of evolution and formed the modern basis of heredity.

Thomas Hunt Morgan, born on Sept. 25, 1866, in Lexington, Ky., was the son of Charlton and Ellen Morgan. He was descended on both sides from English Cavalier stock. In 1886 he entered the State College of Kentucky and later studied at Johns Hopkins University, where he divided his time between morphology and physiology. In 1890 he received his doctorate for a paper on the embryology and phylogeny of sea spiders. In 1891 he served as professor of biology at Bryn Mawr College, after which he went to Europe for further study, first in Germany and then at the famous zoological station at Naples, Italy. There he met Hans Driesch, the philosopher-scientist who believed in "vitalism." Morgan, however, favored a mechanistic approach to the...