The Phylum Ctenophora is comprised of the comb jellyfish. They are planktonic, nearly transparent animals named for the eight rows of comb plates, known as ctenes, that are used for movement. The plates are made of very large cilia and when they beat, the jellyfish moves. They are weak swimmers, however, and are mostly found in surface waters. Their movement consists of only going up or down. These animals also exhibit radial symmetry, like the Cnidarians. During the day, their bodies appear iridescent. At night, nearly all ctenophores give off light or are bioluminiscent.