Cyril Dean DarlingtonDied 26 Mar 1981 at age 77 (born 19 Dec 1903). British biologist whose research on chromosomes influenced the basic concepts of the hereditary mechanisms underlying the evolution of sexually reproducing species. He elucidated the behaviour of chromosomes during the formation of gametes (meiosis). Knowing that Thomas Hunt Morgan had shown that portions of homologous chromosomes cross over (are exchanged), Darlington recognized that this applied to evolution. He formulated a theory of evolution in which the inherited characteristics of the next generation are variable, determined by this crossing over mechanism.