1.In Cnidarians, the body enclose coelenteron cavity, hence the name coelenterata is given to this phylum.
2.Coelenterons has only one aperture mouth. Anus is absent, coelenteron is lined by gastrodermis. e.g., Hydra, Aurelia, Physalia, Adamsia, Pennatuta etc.
1.In sponges, the body wall enclosed a large cavity called spongocoel.
2.Spongocoel is lined by flagellated choanocytes. Water current enter through dermal ostia (pores) and after going through spongocoel, water goes out by osculum. e.g., sponges like Scypha, Euplectella, Leucosolenia.