148 PLAT VHELMINTHES. 
with the muscular movements of the host, the embryo is 
worked into the blood-vessels of the pig, along which it is 
carried into the muscles. Here it loses its hooks and be- 
comes a hollow vesicle or cyst. The wall of the oval cyst is 
invaginated at one side and forms a pocket. On the wall of 
the pocket are found suckers and hooks, and it is later 
evaginated to form the cestoid worm. Pork containing such 
cysts is known as “measly.” This is known as the cystic stage 
or bladder-worm, and the cysts of Zenia solium were known 
Fig. 84.—‘‘ MEas_y” Pork. 
The oval bodies are cysts. 
by the separate name of Cystzcercus cellulose before their 
true nature was determined. The completed bladder-worm 
shows a large bladder, depending from which is the ‘“‘ body” 
of the worm. On being introduced, still alive, into the 
human subject the bladder, and with it the greater part of 
the body, is lost, and the head alone survives as a creeping 
worm, fixes itself and grows into the tapeworm. 
We may note that there is xo true metagenesis, since the 
fission into proglottides can hardly be regarded as a method 
