The sponges constitute the phylum Porifera. The cells of sponges are capable of independent existence, as though they were Protozoa, for as much as two to ten days. That they are not Protozoa is demonstrated by their incapability of indefinite independent existence, and by the fact that their organization comprises two or more types of specialized somatic cells. The morphologic unit of a sponge is a chamber made of colloidal material and amoeboid cells; the latter secrete the jelly, and generally other skeletal material as well. On the inner walls of the chamber occur numerous flagellate cells, distinctively characterized by a transparent collar about the base of the single flagellum. The uncoordinated beating of flagella creates a current which enters by numerous small openings (prosopyles) and leaves by a single larger opening (apopyle). Three levels of sponge architecture exist. The ascon type consists of a single chamber. The sycon type consists of many radially arranged chambers, each opening into a central, axially placed exhalant canal (apochete). The rhagon type consists of many such apochetes emptying with one or more cloacas. There may also be inhalant canals or prosochetes. It is customary to refer to the final exits from sponges as oscules, and to the many entrance apertures as pores. The nutrition of sponges is not well known. Various shallow-water species that are full of algal symbionts may use these as food. The many sponges that live where photosynthesis is impossible must have a different diet. One author has published articles,...