Usually the first part of an organism that enters a new environment is the head. A network of flame cells used to sweep nitrogenous waste out of the body. A primitive digestive system consisting of a mouth, pharynx and branched gastrovascular cavity. Flatworms exhibit two forms of life styles, free-living and parasitic. The parasites exhibit a complex life cycle usually involving several intermediate hosts.
Tapeworms are intestinal parasites that usual infest mammals.
They are rather long flat animals sometimes growing to lengths of 40 feet. The scolex contains a ring of hooks at its tip and is ringed with lateral suckers. The neck is where the proglottids or body parts grow from. The animal does not contain a mouth nor digestive organs, since it lives off of the host's digested food. The animal self fertilizes and sends it eggs out of the host along with the fecal material.