Abstract
The intertidal distributions of the two varieties of Actinia equina L. defined by Stephenson (1935), var mesembryanthemum and vai.fragacea, have been studied on several shores of the English Channel. The reproductive physiology and iso-enzyme genetics of sympatric populations of the two taxa have been investigated in greater detail on one shore. The genetic results show that the two taxa are reproductively isolated and, overall, the evidence indicates that they are separate species.