Abstract
Submersible observations have been made on‘ patches’ of the deep-water coral Lophelia pertusa (L.) occurring on Rockall Bank, north-east Atlantic. It is suggested that an initial colony gives rise to a ring of younger colonies. These in turn give rise to further rings of colonies, thus enlarging the ‘patch’. The transition from stage to stage depends on portions of living colonies, weakened by clionid sponge attacks, breaking off and falling away from the colony so providing the substrate for the development of later colonies, thus enabling lateral increase in the size of the ‘patch’ to take place.