Anemones are related to corals, hydroids and jellyfish. All are in the Phylum Cnidaria (pronounced Ni - dar - e - a). If you imagine an anemone upside down, floating in the water, you can begin to see the similarities. There are two basic types of cnidarians. One is a polyp form, which lives on the bottom, with tentacles reaching up. The other is a free swimming animal, with tentacles generally hanging down, called a medusa. Some cnidarians, at a certain point in the animal's life cycle, exhibit both a medusa phase and a polyp phase. However, anemones and corals do not have a medusa stage. Therefore, they are considered to have a distinct evolutionary path, so are part of a sub-group of cnidarians, Class Anthozoa.