400 CYSTIC TAPE-WOEMS. 



such, belongs exclusively to this group ; on the contrary, the other 

 Tseniadae are also mostly bladder-worms in their youth, as has been 

 formerly noted in discussing their development. But the bladder- 

 worm stage of the latter represents a less perfect organization, not 

 only on account of its smaller size, but especially on account of the less 

 developed state of the embryonic caudal bladder. On these grounds, 

 therefore, there is some reason for distinguishing them from the true 

 Cystici, and we will in the meantime designate them " Gysticercoidd." 



Geoup a. — Cystic Tape- Worms {Cystici). 



Tschudi, " Blasenwiirmer, " Freiburg i. B., 1837. 



Von Siebold, "Band- und Blasenwiirmer :" Leipzig, 1854. 



Leuokart, "Die Blasenwurmer und ihre Entwiokelung : " Gieesen, 1856. 



Moniez, "Essai monogr. sur les Cystereerques," Trav. instit. zool. Lille, t. iii : Paris,1880. 



These tape-worms are mostly of apprecialle, and sometimes even of 

 considerable size. The head is very rarely unarmed, tut is always 

 provided with a strongly muscular, lenticular, slightly projecting 

 rostellum, and a double, in some cases even triple, circle of hooks, which 

 decrease in size, and often change their form in the posterior rings. 

 Besides the claiu, one can always distinguish two strong root-processes, 

 running one anteriorly, ^ the other posteriorly, of which the latter is the 

 longer, especially in the anterior row. The proglottides, when ripe, are 

 of a longish oval form, and have a uterus whose longitudinal main stem 

 runs up the middle line, and in course of time develops a number of 

 more or less independent, generally much divided, lateral branches. The 

 vagina runs from the middle of one side downwards in a curve to the end 

 of the uterus, and there comes into connection with the common duct 

 of the tvjo hand-shaped ovaries, and of the yolk-gland lying behind these. 

 The testes are numerous, and are diffused throughout the whole body. 

 The generative openings are found in irregular alternation on the right 

 and left sides. The cirrhus-pouch and seminal vesicle are of small size. 

 On the eggs one finds round about the embryo a firm shell of a brown 

 colour, and a more or less distinctly granular character, which is originally 

 surrounded by a second clear and distinct envelope. The embryonic 

 hooks are short and thin, and all the six are of uniform structure. 



In both stages they live exclusively, so far as we know, in the Mam- 

 malia; as tape-worms, especially in Carnivora; as bladder-worms, 

 especially in Rodentia and Buminantia. 



^ [The reader is reminded that these words refer to the hook itself, not to the whole 



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