84 INVERTEBRATE ZOOLOGY 



another animal, called the intermediate host, which is itself preyed 

 upon by the host. After being thus transferred to the stomach 

 of the intermediate host there hatches from each egg a minute 

 spherical embryo, called the six-hooked embryo, which is provided 

 with three pairs of hook-like organs of locomotion. This 

 embryo works its way through the wall of the intestine of the 

 animal and migrates finally to some one of the internal organs, 

 where it lodges and grows into a cyst-like larval form, called 

 the cysticercus. Within the cysticercus is a fully developed 

 scolex, but turned wrong side out. If, now, the intermediate 

 host be eaten by the host, the scolex turns right side out, passes 

 into the intestine of the latter, attaches itself to the intestinal 

 wall, and grows into an adult tapeworm. 



The intermediate host of Taenia saginata is the beef, in the 

 muscles of which the cysticercus will be found, if present. 

 That of Taenia serrata is the rabbit and that of Taenia erassi- 

 collis is the mouse; in the former animal the cysticerci are 

 imbedded in the peritoneum or the liver, and in the latter, in 

 the liver. Open the body-cavity of either of these latter ani- 

 mals by a median ventral incision and look for cysticerci. They 

 are large, whitish bodies and are easily detected if present. 

 When a cysticercus is found, it should be carefully dissected 

 out, its outer wall slit and the scolex exposed to view. Mount 

 it on a slide in dilute glycerine and study it. 



Exercise 7. Draw a view of the scolex in its cyst. 



