True tapeworms; body divided into . Amphilina, Gyrocotyle. scolex, neck, and strobila; strobila composed of many proglottids ; both male and female reproductive systems in each proglottid; of vertebrates adults in digestive tract . Proteocephalus, Taenia, Echinococcus, Taeniarhynchus; Diphyllobothrium. About 1,000 species