Within the Central Pacific, atolls make up the largest percentage of the land mass. Various workers have suggested that many of the physical features of an atoll are due to the growth of its benthic algae. Thus, when a coincidence of interest and technique recently made it possible, a study of the distribution of the benthic algae and the factors effecting this distribution was initiated and carried out at Eniwetok Atoll in 1955-1956 (Fig. 1).