Cestoda is a class of parasitic flatworms, commonly called tapeworms, that live in the digestive tract of vertebrates as adults and often in the bodies of various animals as juveniles. Taenia saginata, the beef tapeworm, can grow up to 40 feet long (12 m); other species may grow to over 100 feet (30 m). Symptoms According to The Merck Manual, Tapeworm infestation doesn't usually cause any symptoms. Infection is generally recognized when the infected person passes segments of proglottids in the… (More on Tapeworm)