The Cnidarians share a few characteristics that defines them. They have radial body simmetry (with the arrangement of body parts around a central axis) and they also have tissues. They present polyphormism, and they can have two body forms (polyp or medusa). They also are diplolastic, which menas that their bodies derive from only two embryonic cell layers. The five questions of Cnidarians are Anthozoa (including corals and anemones), Schyphozoa (like the swimming jellyfish), Staurozoa (like the stalked jellyfish), Cubozoa (box jellyfish) and Hydorozoa (the hydroids and siphonophores).
