Cnidaria
The Phylum Cnidaria are organisms that are aquatic invertebrates. The all have an internal cavity, tentacles, and stinging cells. Some types of cnidarians are jellyfish, hydras, anemones, and corals. Cnidarians also have one single opening that food is ingested and excreted from. Cnidarians lack organs and posses a primitive nervous system known as a neural net.