258 



PLATYHELMINTHES. 



FIG. 214,BothriocepMlus latus (after 

 Leuckart). 



FIG. 215. Encysted larva of Bothrio- 

 cephalus from the Smelt (after 

 Leuckart). 



(Fig. 216, a), situated at some distance behind 

 the other two ; this is the opening of the 

 tubular uterus (Ut), the convolutions of 

 which give rise to a peculiar rosette-shaped 

 figure in the midst of the segment. Close 

 to the hind end of the segment the ducts of 

 the yolk-glands (Dst] and of the ovaries (Ov) 

 unite with each other and open into the 

 uterus ; the cells of the shell -gland (Sd) 

 surround and open into the point of junction 

 of thesestructures. 



The ova are for the most part developed 

 in water, and escape from the upper pole of 

 the egg-shell through a lid-like valve (Fig. 

 204). The escaped embryo is covered with 

 cilia (Fig. 203), by means of which it swims 

 about for a long time. The encysted larval 

 form (scolex without a bladder) is found 

 between the muscles or in the viscera of the 

 pike, turbot (Lota vulgaris), and possibly of 

 other fresh-water fish (Fig. 215). How they 

 become infected is not known, as experiment 

 tends to show that the ciliated larva does not 

 enter them directly, and no intermediate host 

 is known. The scolex enters the body of its 

 final host in the flesh of the fish. B. cordatus 

 Lkt. With large, heart-shaped head, without 

 a filiform neck ; with deposits of numerous 

 calcareous bodies in the parenchyma. It 

 attains a length of about three feet, and 

 lives in the intestines of man and of the 

 dog in Greenland. B. liguloides Lkt. Young 

 form about 20 cm. in the subperitoneal tissue 

 of man in China and Japan. 



ScMstocephalus Crepl. Head split, with a 

 sucker on each side. The body of the cestoid 

 form is segmented. S. solidus Crepl. Lives 

 in the body cavity of the stickleback, escapes 

 into the water, and becomes sexually adult 

 in the intestine of water-birds. Triaeno- 

 phorus Rud. Head not distinct, with two 

 weak suckers and with two pairs of triden- 

 tate hooks. The body has no external seg- 

 mentation. The generative openings are 

 marginal. T. nodulosus Rud. In the intes- 

 tine of the pike. Asexual encysted form in 

 the liver of Cyprinus. Bothrimonus Duver- 

 noy, intestine of sturgeon. 



Ligula Bloch. Body band-shaped and un- 

 segmented. Without real suckers. Hooks 

 may be present or absent. The Cestoid has 



