///. 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. 24U. 



Fig. 241. 



Fig. 242. 



Fig. 240.— Apical view of head of Taenia solium. (From Hatsclieli.) 



Fig. 241. — Head of Tetiarhimchus viridis. (After Wagner.) Dissected to snow tbe 



internal parts of the proboscides (o) and tlie .t^anglion (ft). 

 Fig. 242. — Schema of action of rostelLum. On the right the hooks are exserted for 



adhesion, on the left retracted. i\ rostellum; y, sheath; /, longitudinal muscles. 



0' 



^ 



jo o^O o%'?,i, o^ 



OOQJ^ 



I'U od sd dg u 01/ 



Fig. 243.— Proglottis of Bothriocephcdus latus. (After Sominer.i Right only vitel- 

 larium, left only testes, shown, ch, cirms sheatli opening with the vagina; dri, 

 vitelline duct; dt, vitellarium; h, testes; od, oviduct; oi\ ovary; sd, shell gland; 

 n, uterus; va, vagina; I'd, vas deferens (dark-lined; ; w, 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. I'jesides cross-fertilization 

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

 two types mav l)e made out from figures 2-13 and 2-14:, reference 



