Phylum Cnidaria (formely known as coelenterata) includes about 9000 species.Some are found in fresh water, but the grater number are marine. Coelenterates (Gr. koilos, hollow+enteron,gut).are the simplest of eumetazoans. This interesting group of animals take its name from the large cavity in the body that serves as the intestine.They include the hydra, jellyfish, sea anemones and corals.
