Marine biologist, born on 19 January 1898 at Burnham-on-Sea, the son of the Rev. Dr. Thomas Stephenson. His father (born at Brackley; e.m. 1891; died 15 April 1948) was Assistant Tutor at Richmond College 1891-1894 and 1898-1904, Fernley Lecturer in 1930 and an authority on British orchids.
Educated at Kingswood School, he inherited his father's interest in natural history and his mother's artistic skills. Under the patronage of the geographer H.J. Fleure, he became interested in sea anemones and in 1916 was appointed student-demonstrator at the University College,Aberystwyth. His research and published work won him an MSc in 1920 and DSc in 1923, when he was appointed lecturer in zoology at University College, London. His two volumes on British Sea Anemones illustrated by the author, were published in 1928 and 1935. He was a member of the Great Barrier Reef Expedition which explored the Queensland coral reefs in 1928-29 and from 1930 to 1940 was Professor of Zoology at the University of Cape Town. With his wife he made close studies of the coastal ecology of South Africa and the east and west coasts of North America. His contribution to our knowledge of intertidal marine life and his artistic skills were recognized when he was elected FRS in 1951. He died in London on 3 April 1961. A book on Life between Tidemarks on Rocky Shores, completed by his wife, was published posthumously in 1972.