Jellyfish - the animals, which are all associated with something shapeless and extremely primitive, but their way of life and physiology is not as simple as it seems at first glance. The word "Medusa" usually implies animal from the class Scyphoid and representatives of the detachment Trailed of class Hydroid type Coelenterates. At the same time, in the scientific environment, this word has a wider interpretation zoologists indicate this term any mobile form coelenterates animals. Thus jellyfish are in close relationship with movable types coelenterates (siphonophorae, sea ships) and seat - corals, undigested, HYDR. In total there are more than 200 species of jellyfish.
