THE TAPEWORM 



101 



granules of calcium carbonate, and the cuticular membrane covering 

 the body. Where is the digestive tract? Which of these features are 

 related to the parasitic habits of the. animal? 



(d) Tapeworms are hermaphroditic. Typically, each proglottid 

 contains one complete set of male and female reproductive organs. 



prog/o/ffds ~ , ^ 



£>co/<2^ 



Fig. 50. — ^Life-cycle of Tsenia solium. A, parts of the worm, showing the 

 youngest proglottids behind the scolex and the oldest (ripe) proglottids at 

 the end of the worm. B, scolex of an adult tapeworm. C, six-hooked embryo 

 inside its shell and the tough surrounding capsule. D. six-hooked embryo freed 

 from its shell. E, portion of a muscle in which are embedded bladder-worms; 

 successive layers are removed to show internal structures. F, juvenile tape- 

 worm which arises from the bladder-worm by evagination of the scolex. 



(From W. Stempell, "Zoologie im Grundriss," 1926.) 



The male reproductive system consists of numerous testes each of 

 which discharges sperm through a ductus efferens (vas efferens) . These 

 ducts unite to form a single ductus deferens (vas deferens) which 

 passes to the outside through the penis, located on one edge of the 

 proglottid and protrusible from the genital pore. The female repro- 

 ductive system consists of paired ovaries discharging ova through 



