Sponge

sponge, any of the primitive multicellular aquatic animals that constitute the phylum Porifera. They number approximately 5,000 described species and inhabit all seas, where they occur attached to surfaces from the intertidal zone to depths of 8,500 metres (29,000 feet) or more. The members of one family, the Spongillidae, are found in fresh water; however, 98 percent of all sponge species are marine. Adult sponges lack a definite nervous system and musculature and do not show conspicuous movements of body parts.