Defining Characteristics

Members of the phylum cnidaria are radially symmetrical animals with a simple form, all with stinging capsules used for defense and to capture food. These capsules are activated when chemically or mechanically stimulated. Species appear as polyps (sea anemones) or medusa (jellyfish), and often a species goes through both forms in its life cycle (jellyfish, hydroids). Cnidarians live in the sea except for a few (e.g. hydra) that inhabit fresh water.

Cnidaria Links

http://ourworld.compuserve.com/homepages/BMLSS/Cnidaria.htm