Scyphozoans exhibit the main characteristics of cnidarians. They have radial symmetry and are diploblastic, meaning that their body wall consists of the outer epidermis (ectoderm) and the inner gastrodermis (endoderm), which are separated by mesoglea. They have nematocysts, which are characteristic of the phylum. They undergo alternation of generations, with the medusa form being dominant. Scyphomedusae are the "jellyfish" with which most people are familiar.
Scyphozoan polyps and medusae exhibit no cephalization and contain no brain, but in some species, light-sensitive eyespots are located along the bell margin of the medusa. http://animaldiversity.org/accounts/Scyphozoa/ |