THE TAPE WORM 



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become fixed in the muscle or other tissues of the body. The 

 larva develops into a bladder-like, cysticercus, in which are 

 formed one or more embryonic scoleces. In this condition it 

 remains until the flesh in which it is embedded is eaten by a dog. 

 Then the scoleces are set free. They attach themselves to the 

 wall of the intestine by means of the suckers and hooks, and 

 then develop the tapeworm strobila. In this case the develop- 



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 400 





r 



Fig. 233. — Diagram of the tapeworm, Tsenia. A, Cysticercus or bladder- 

 worm stage. 5, later stage of same. C, Strobila. The last proglottis shows the 

 uterus which is filled with embryos; D, one of the embryos in the egg shell; b, 

 bladder; ex, excretory canals; g, genital pore; h, scolex with hooks and suckers 

 (5); «, uterus; 2, zone of strobilation. Some of the proglottides are numbered; 

 many are omitted. (From Galloway.) 



ment is simpler than that of the fluke, and asexual multiplication 

 may be confined to the strobila, as when the cysticercus de- 

 velops only one scolex. There is, however, always an alter- 

 nation of hosts. There are many kinds of tapeworms, each 

 with its specific two hosts. Thus, one tapeworm of the dog 

 finds its other host in the dog flea. Others alternate between 

 cat and mouse, goose and crayfish, man and fish, man and swine, 

 man and dog, etc. The tapeworm is a dangerous parasite, not 

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