INTERNAL PARAiITES. (eNTOZOA.) 



225 



" One of the strangest points connected with this entozoon 

 is the extraordinary provision made for its propagation. In 

 ordinary cases one tapeworm only results from the growth 

 of the products of a single egg; but here we may have thou- 

 sands of tapeworms all resulting from a solitary germ." 



He thus explains it : 



"Eggs escape from the dog per antim. One swallowed 

 by any herbivorous animal, say a sheep, will (by a lengthened 

 process of development, the details of which I need not give) 

 eventuate in the formation of hydatids. These hydatids, 

 under favorable circumstances, will by internal budding 

 produce innumerable heads or scolices (Fig. 29, B), each of 

 which display the tsenia-like crown of hooks (a), the suckers 

 Qi), the calcareous particles (/), and a vesicular body (d). 



When, therefore, a dog is fed on the viscera of a sheep 

 containing perfect hydatids of this description, all the numer- 



Flg. 30. 

 Group of Echinococcus Heads. (Cobbold. 



ous heads become developed into tapeworms in the animal's 

 intestines. This has been proved over and over again by 

 experiment. 



" Most of the heads are developed in delicate sacs, termed 



