As a member of the Phylum, Cnidaria, hydra arose early during metazoan evolution before divergence of the protosome and deuterostome branches. Its body plan is organized as a gastric tube with a ...

Hydra is a genus of tiny freshwater organisms within the phylum Cnidaria-- the phylum that includes jellyfish, sea anemones and corals, among others. Most hydra measure less than half an inch.

Hydra are inch-long freshwater creatures that resemble a floating tube with a grasping appendage at one end and a cluster of tentacles at the other. They belong to the phylum Cnidaria ...