Hydrozoa cnidocytes present in epidermis gametes produce epidermally and always released to the outside of the body mesoglea is largely acellular medusae usually with a velum many polyps are colonial mostly marine with some fresh water species Examples: hydra, obelia, gonionemus, physalia
Obelia
Haliclystus californiensis
Staurozoa medusae absent develop from benthic planula larvae 8 tentacles surrounding the mouth attachment to substrate by adhesive disk sexual reproduction only marine Example: haliclystis
Scyphozoa medusa prominent in the life history polyps small gametes gastrodermal in origin and released into the gastrovascular cavity cnidocytes present in the gastrodermis as well as the epidermis medusa lacks a velum mesoglea with wandering mesenchyme cells of epidermal origins marine examples: aurelia
Chrysaora achlyos
A cubozoan of the genus Chironex
Cubozoa medusa prominent in life history polyps small gametes gastrodermal in origin medusa cuboidal in shape with tentacles that hang from each corner of the bell marine examples: chironex
Anthozoa colonial or solitary polyps medusa absent cnidocytes present in gastrodermis cnidocils absent gametes gastrodermal in origin gastrovascular cavity divided by mesenteries that bear nematocyst internal biradial or bilateral symmetry present mesoglea with wandering mesenchyme cells tentacles solid marine anemones and corals example: metridium