III. CESTODA. 



281 



regarded as sexual individuals of a colony, each with its own 

 reproductive apparatus. Two types must be recognized. In the 

 one the presence of vitellaria and the separate openings of uterus 

 and vagina recall the conditions in trematodes, while in the second 



FIG. 240. 



FIG. 242. 



FIG. 240. Apical view of head of Tcenin solium. (From Hatschek.) 



FIG. 241. Head of 'Jetmrhuuchus viridis. (After Wagner.) Dissected to snow the 



internal parts of the proboscides (<>) and the ganglion (a). 

 FIG. 242. Schema of action of rostellum. On the right the hooks are exserted for 



adhesion, on the left retracted, r, rostellum; s, sheath; /, longitudinal muscles. 



#2 od sd dg u ov 



FIG. 243. Proglottis of Bothriocephalus latus. (After Sommer.) Right only vitel- 

 larium, left only testes. shown, cb, cirrus sheath opening with the vagina; d<7, 

 vitelline duct: dt, vitellarium: /i, testes; od, oviduct; ov, ovary; sd, shell gland;, 

 tt, uterus; vci, vagina; vd, vas deferens (dark-lined); 10, excretory canal. 



the uterus ends blindly and the vitellaria are modified into a small 

 albumen gland. Since vagina and vas deferens almost always open 

 together, self -impregnation is possible. Besides cross-fertilization 

 of separate proglottids has been seen. The general features of the 

 two types may be made out from figures 243 and 244, reference 



