outlines of zoology zoology 146 ccelentera of hollow tentacles around the oral disc the mouth is usually a longitudinal slit the tentacles are contracted when the animal is irritated and the whole body can be much reduced in size just below the margin of the oral disc there is a powerful sphincter muscle this contracts and pulls together the body wall over the mouth and retracted tentacles water may pass out gently or otherwise by a pore at the tip of each tentacle and long white threads richly covered with stinging cells can be ejected in many anem ones through the walls of th rdp06g.jpg from leafa　tentacles View Photo