The flukes are parasitic flatworms. Flukes characteristically possess suckers, usually two or more, used to attach themselves to their host. Much of a fluke's body cavity is occupied by reproductive organs. Flukes may be either external or internal feeders, and some fluke groups have extremely complicated life histories. The Cestoda are made up of the tapeworms.
Tapeworms are internal parasites of vertebrates.
Each segment is a reproductive sack and as it ripens it breaks off and pass to the outside of the host in its feces. To find out more about the Platyhelminthes, visit the links listed below. Introduction to the Platyhelminthes . University of California at Berkeley, Museum of Paleontology. A great introduction to the Platyhelminthes.