Distinguish between Nonchordata and Chordata.
A polyp is a cylinder with tentacles at the top. The Hydra looks like a tin with slender arms coming from the top of its body. This body form does not move and the animals are trappers. The medusa is an umbrella shaped structure with tentacles hanging down from it. The jellyfish is an example. These animals move. During the reproductive stages of the jellyfish there is a time when they take on the polyp form. Then they bud off and become medusa.