Cnidaria - Anemones Cnidaria Members of the Phylum Cnidaria include the Anemones and are grouped with the soft and hard corals and the hydroids. Cnidarians all have a life cycle of two forms. One is a free-swimming jellyfish medusa stage and the second is an attached polyp stage.
Cnidarians have a radially symmetrical body shape with a mouth surrounded by rings of tentacles.
The two life stages of Cnidaria have similar simple body parts. This structure is where the group gained its earlier name Coelenterate . The coelenteron is a gastrovascular cavity which also acts as an alimentary system, a circulatory system and a coelom . The body wall has three layers. There is an outer cellular epidermis , an inner cellular gastrodermis and a complex gelatinous layer between called the mesoglea .