Phylum Cnidaria ("nettle")
Description
Over 10,000 species belong to phylum Cnidaria. Jellyfish, Hydra, Sea Anemones and Corals are among these. They are mostly marine, and are all carnivorous. They are radially symmetrical. Their bodies have tissues, but no organs. They have only two tissue layers: endodermic and ectodermic tissue layers, as well as simplistic muscles and nerves. They have a two way gastrovascular cavity. There are two different shapes of Cnidarians: Medusa, which is like the structure of a jellyfish, or polyp, which is like a Hydra.