Abstract
Further study of the phenomenon of gregariousness during settlement, demonstrated in the oyster Ostrea edulis (Cole & Knight-Jones, 1949; Knight-Jones, 1951) and the barnacle Elminius modestus (Knight-Jones & Stephenson, 1950), seemed to require laboratory experiments, for which a viviparous animal with a brief, lecithotrophic, pelagic stage appeared to be needed.