1G2 ZOOLOGY. 



in the young, and there are no suckers or hooks ; while 

 there is but a single set of male and female reproductive 

 organs situated in the posterior end of the body, which can 



be detached from the ante- 

 rior part of the body, form- 

 ing a. proglottis. In fact, 

 this form is a connecting 

 link between the Treviatoda 

 ^- ■,,, Tj ^ <,r„ . „ and. Cestodes. CaryopJiyllmus 



Fig. 111.— Head of 7". cwftMrws seen from sea 



above, with circle of hoolcs ; a— c, hooks ; mutabUis Eudolphl llVCS m 

 all much enlarged .—After Sieboia. . » ^ ■ -i 



the intestines of Cyprmosa 

 fishes ; the young in a worm, Tuhifex rivulorum. 



Tetraryhnchus is provided with four very long slender 

 extensile spiny cephalic processes or beaks. The young live 

 encysted in bony fishes, the adults occurring in the intestines 

 of sharks and rays. 



In Ligula the body is ribbon -shaped, not Jointed, with a 

 series of sexual organs, and there are no suckers, and some- 

 times no hooks. L. simplicissima Kud. lives in fishes and 

 amphibians, and attain maturity in the intestines of water- 

 birds, which feed on the former animals. This genus con- 

 nects the simpler tape-worms with BothriocepJialiis and 

 TcBfiia. 



Class I.— PLATYHELMINTHES. 



Mare or less flattened worms, with the body usually unsegmented ; tTie 

 liead in the Cestodes often armed with hooks or suckers. Simple or branched 

 (Turhellaria) or forked {TVematoda) digestive tract, but no general body- 

 cavity. (The digestive camty is entirely wanting in the Cestodes.) Ner-cous 

 system represented by a double cephalic ganglion, with two or more nervous 

 cords. A system of vessels corresponding to the water-vascular system of 

 Echinoderms, hat supposed to be mainly excretory in function. Monce- 

 cious, rarely bi-sexual. Ovaries differentiated into a germigene and viteU 

 logene ; often parthenogenetic, accompani'd by strobilation in the tape- 

 worms. When idternaiion of generations occurs by budding, the sexual ani- 

 mals are united with their nurse or a sexwdform into a polymorphic colony. 

 Order 1. Turbellaria. — Flattened ovate worms, with a nervous gan- 

 glion in the head ; usually eye-specks ; body externally cili- 

 ated, with a much-branched digestive canal. Nettling 

 organs often present. Bisexual, rarely unisexual; strobi- 



