Hydroids, Jellies and Coral

Overview

These animals have a simple body plan with a single internal cavity containing both their digestive and circulatory functions. A single mouth is its only opening and tentacles usually surround it. All members have stinging cells (nematocysts) usually found on the tentacles and are used in the capture of prey. Hydrozoa is usually colonial, Scyphozoa includes the mobile jellies, and Anthozoa are the polyp form anemones and corals.