Between these two layers is a gel like substance called mesoglea. Sometimes the mesoglea contains cells and connective tissue. Only one oral opening is present in Cnidarians, and therefore serves as both a mouth and an anus. The animals use their tentacles, covered with stinging nematocyst cells, to kill or paralyze prey and then pull it to the mouth. It is passed into the gastrovascular cavity, where digestible material is broken down and eaten.
Indigestible material is spit back out.
Cnidarians do not have a brain, however, they do have sensory cells which tell them information that is necessary for survival. When it comes to muscles, Cnidarians don't stand for much. Their muscles consist of an outer layer of longitudinal fibers at the base of the epidermis and an inner layer of circular fibers at the base of the gastrodermis. However, the lack of muscles does not impair the mobile Cnidarians' movement. They use jet propulsion by sucking water into the gastrovascular cavity and then spitting it out in a strong spurt of water to move themselves.