Cell biologist, born in Charleston, South Carolina, USA. He was a teacher and researcher at Howard University (1907‚Äö√Ñ√¨41), and also studied at the Woods Hole (MA) Marine Biological Laboratory. He made pioneering contributions to the cytology and embryology of marine organisms, and in 1925 demonstrated the carcinogenic effects of ultraviolet radiation on cells. By 1929, the diminishing number of African-American graduate students, his disenchantment with Howard’s attitude towards his need for research facilities, and his feeling that Americans regarded him (an African-American) with more curiosity than respect, caused him to take leave of absence and pursue his studies in Europe.