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 crassi- 
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, 
