OUE DOMESTICATED ANIMALS. 95 



merine tapeworm (Tcenia cucumerina). This entozoon is 

 so named because of the shape of its mature segments or 

 proglottides. The latter are much elongated, narrowed 

 at both ends, each joint being supplied with a pair of 

 reproductive papillae, one on either side of the margin. 

 It is a delicate and almost transparent tapeworm, mea- 

 suring from ten to twenty inches in length. 



This parasite is very common in English dogs, and 

 according to Krabbe infests 48 per cent, of the dogs in 

 Denmark, and 57 per cent, of the dogs in Iceland. The 

 animals infest themselves in a singular manner. The joints 

 of the worm, having escaped jper anum, readily crawl as 

 semi-independent creatures on the coat of the dog, 

 chiefly on the back and side. The eggs thus distributed 

 are readily swallowed by the louse of the dog (Trichodectes 

 latus) . 



In the body of the louse the six-hooked embryo, 

 hitherto contained in the egg of the tapeworm, escapes 

 the shell andbecomes transformed into a minute cysticercus 

 or louse-measle. When the dog is irritated by the lice, 

 it attacks, bites, and frequently swallows the offending 

 external parasite. In this way the louse-measle is trans- 

 ferred to the dog's intestinal canal, where, in course of 

 time, it develops into the sexually mature cucumerine 

 tapeworm. 



Thus the mange-mite, or scab insect (as it is rather in- 

 correctly termed) serves as the intermediary bearer of 

 larval tapeworm, and forms an essential factor in the pro- 

 duction of this particular species of cestode parasite. In 

 this connection I may also remark that there is every 

 reason to believe that, so far as the intermediary bearers 

 are concerned, the tapeworms infesting herbivorous 

 animals have a very similar origin. 



