It occurred in Pre-Cambrian times. Before the Cambrian was far along, most of the animal phyla had appeared. So each of the phyla described in this section has had a long, independent history.
Food is taken through a mouth into the gastrovascular cavity .
The cavity is also called a coelenteron and for many years the name of this phylum was Coelenterata . There is no anus. Although the freshwater hydra is a much-studied representative, it is not typical of the class. The jelly of the medusa is a much-enlarged mesoglea. Anthozoa Sea anemones and corals.