Second volume in the revision of the Porifera. Entirely devoted to introductory material, with chapters on general features of the Porifera; morphology, phylogeny, and classificaton of the Demospongea, Lyssacinosa, and Hexactinellida; glossary; reproduction and development; physiology; functional morphology and adaptation; variability and variation; ecology and paleoecology; evolution and ecological history; geographic and stratigraphic distribution; and techniques of study. Also included are a comprehensive reference list and an index.