82 BOARD OP AGRICULTURE. 



this condition the creature has a flask-shaped form. The neck 

 tapers gradually from the bladder to the head, and is divided 

 transversely into a series of many short joints. The head is 

 but little enlarged, bearing four suckers, as usual, and in the 



Figure 60. 



Figure 61. 



center has a proboscis, surrounded by two rows of hooks, con- 

 taining from sixteen to twenty-four pairs. Sometimes there 

 are found in large bladders of this kind a few secondary blad- 

 ders attached to the inside of the large one, produced by a 

 process of budding, somewhat as in the water-brain, or coenu- 

 rus. This parasite, as thus characterized, was formerly sup- 

 posed to be a distinct and peculiar species, and received the 

 name of " Cysticercus tenuicollis" or slender necked bladder- 

 worm. Recent investigation and experiments have, however, 

 proved it to be only the young or larval condition of one of the 

 common tape-worms of the dog (Tcenia marginata). Blad- 

 der-worms of the same kind are found, though less commonly, in 

 cattle and horses, as well as in pigs, monkeys, and many other 

 animals, and very rarely in man. Owing to the large size to 



Figure 60. Diving bladder-worm, from a sheep ; natural size. Hearth and 

 Home, after Thudichum. 



Figure 61. Head of Ttenia marginata, enlarged. Hearth and Home, after 

 Thudichum. 



