CESTODES : GENERATIVE ORGANS 



199 



receives the germinal cells and advances them further. After the 

 union of the oviduct with the spermatic duct the canal proceeds as 

 a duct for fertilisation, and after only a very short course takes 

 up the vitellogene gland or glands and then the numerous ducts 

 of the shell gland (ootype). The vitellogene gland may be a single 

 one. but often exhibits the primitive duplication more or less dis- 

 tinctly, in which case it is situated at the posterior border of the 

 segments in the medullary layer (fig. 125). The original position of 

 the doable, organ is then the same as in the trematodes, i.e., at the 

 sides of the proglottides, and thence eventually spreading more 

 or less on both aspects (figs. 126 and 128) ; the gland is dis- 

 tinctly grape-like and the follicles lie mostly in the cortical layer. 



Fxv. M. 



w$$>& ^ 



cp. 



FIG. 127. External aspect of a transverse section through a proglottis of 

 Teenia crassicollis. 44/1. Cp., cirrus pouch, with cirrus and the retractors at 

 its base ; Exv., excretory vessel ; T., testicles ; Lm., longitudinal muscles ; 

 M., medullary fasciculus ; V.d., vas deferens. 



Tire fertilised ova, surrounded by masses of vitellus, receive 

 the shell material at the place of junction of the shell gland, 

 and, as completed eggs, then move onward to the uterus. In those 

 cases in which the uterus in its further course presents a sinuous 

 canal and forms a rosette, as in the liver fluke (Ligula, Triceno- 

 phorus, Schistocephalus, Dibothriocephalus, and others), there is 

 generally an external opening which is usually separate from 

 the genital pore, and lies on the same or the opposite surface. 

 In all other cases, however, the uterus terminates blindly and is 

 represented by a longer or shorter tube lying in the longitudinal 

 axis (fig. 125) ; (in some forms, however, it extends transversely) 



