Abstract
Nauplii from freshly collected adults were fed with the diatom Phaeodactylum tricornutum Bohlin and dried liver powder in mass culture tanks. Details of the method of preparation of food, design of the tank, rate of flow of sea-water, and population densities are given. Low but consistent yields (0.02-3.80 per cent.) of settling cyprids were obtained, the total from five consecutive experiments being 3431. At the locality (Menai Straits, Sorth Wales) natural settling of Elminius modestus Darwin took place in the summer months (May-September) with a main peak about June-July. The above experiments were made during winter (December-March) when natural settling was not detected on exposure plates immersed concurrently in the sea amongst adults of this species.