Cestoda (class)

Members of a class of parasitic flatworms that live in the digestive tract of vertebrates as adults. They are fluid-feeding with a knoblike head provided with suckers and hooks, a short neck, and the rest of the body made up of a series of identical segments packed with reproductive organs. Larvae live within the gut vertebrates and arthropods, adults within vertebrates only, absorbing the hosts' food directly across their body wall; they reach a length of 40 feet in some species.