Clarence E. McClung (1870-1946), US geneticist. McClung is best known for discovering the role of chromosomes in determining gender. He discovered this while working on grasshoppers. He also proposed the term chromatid in 1900, to refer to the condensed units of a chromosome. McClung studied at the University of Kansas, and was a professor there from 1902-1906. He was Professor of Biology at the University of Pennsylvania from 1906. He also worked on palaeontology, and in particular on fish fossils from the Cretaceous period.