CESTODA. 



329 



posterior end of the body, i.e., at the hind end of the last segment, 

 in which a small vesicle with an external opening receives the longi- 

 tudinal trunks. According to the observations of Leuckart on 

 Tcenia cucumerina, the posterior transverse canals in the segments 

 immediately preceding the last become, by their gradual shortening 

 and the approach of the longitudinal trunks, transformed into the 

 vesicle, which acquires an external opening when the segment behind 

 it is detached. In rare cases the excretory system possesses additional 

 openings in the anterior part of the body behind the suckers. 



The generative apparatus is also divided into segments which 

 correspond to the proglottides. Each proglottis possesses its own 



FIG. 265. Proglottis of Tcenia mediocanellata, with male and female organs (after Sommer). 

 Ov, ovary ; DS, yolk gland (vitellarium) ; Sd, shell gland ; Ut, uterus ; T, testea ; Yd, vas 

 deferens ; Cb, pouch of the cirrus ; J5T, generative cloaca; Va, vagina. 



male and female generative organs, and can therefore, when separated, 

 be considered as a sexual individual of a lower order. The male 

 apparatus consists of numerous pear-shaped vesicles, the testes (fig. 

 265, T), which are situated upon the dorsal side, and their vasa 

 efferentia open into a common efferent duct (vas deferens). The coiled 

 end of this duct lies in a muscular pouch (cirrus sheath), whence it 

 can be protruded through the genital opening as the so-called cirrus. 

 This cirrus is frequently beset with spines which are directed back- 

 wards, and serves as a copulatory organ. The female generative 

 organs consist of ovary, yolk gland, shell gland, uterus, receptaculum, 

 and vagina. The vagina and vas deferens usually open into a common 



