They have a radial symmetry; they have an up and down side.
They are diploblastic, which means that they have 2 germ layers, endoderm and ectoderm.
The new development is that of tissues, special parts that have a special function; simple nerve system and muscles.
Cnidarians: comb jelly fish
Ctenophora: comb jellies
Subphylum Medusozoa—jellyfish and hydrozoans
Class Cubozoa—box jellyfish, sea wasps
Class Hydrozoa—hydroids, hydra-like animals
Class Scyphozoa—true jellyfish
Class Staurozoa—stalked jellyfish
Anthozoa: sea anemones, corals, sea pens, wholly sessile.
Scyphozoa: jellyfish, swimming.
Cubozoa: box jellies.
Hydrozoa: diverse, freshwater cnidarians, sessile members, such as Hydra, and colonial swimmers, such as the Portuguese Man o' War.
Staurozoa: highly derived parasitic Myxozoa.
Polypodiozoa: intracecllular parasites.
Placozoa: basal form of marine free-living, non-parasitic. multicellular organism.