296 



THE ANIMAL PARASITES OF MAN 



the oviduct is continued as a shorter or longer tube, the uterine canal 

 or true oviduct opening into the uterus proper. J. W. W. S.] 

 The vitellarium may be single, but often exhibits its primitive 

 duplication more or less distinctly, in which case it is situated at the 

 posterior border of the segments in the medullary layer (fig. 191). 

 The original position of the double organ is, moreover, the same 

 as in the Trematodes, i.e., at the sides of the proglottids, and thence 

 eventually extending more or less on both surfaces (figs. 192 and 194) ; 

 the gland is then distinctly grape-like and the follicles lie mostly in 

 the cortical layer. 



The egg cell that has been fertilized and supplied with yolk cells 

 receives the shell material at the point of entry of the shell gland ducts, 

 and, as a complete egg, then moves onward to the uterus. In those 

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

 canal, and may form a rosette (pseudo-phyllidea), there is an external 



Vvs. 



m. c. 



FIG. 194. Part of a transverse section through a proglottis of Dibothriocepkalus lalus. Ct.> 

 cuticle; C., cirrus; Vvs. t vitelline follicles; L.M., longitudinal muscles; T. t testicles; 

 Af., medullary nerve ; S.c. t subcuticle ; T.m., transverse muscles ; #., uterus. 20/1. 



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 sac 

 lying in the longitudinal axis (fig. 191), but in many forms trans- 

 versely. With the accumulation of eggs it becomes modified in 

 various ways : (i) it sends out lateral branches (fig. 241), or (2) forms 

 numerous isolated sacs (PARENCHYMAL CAPSULES) containing single 

 eggs or groups of eggs (fig. 217) ; further, (3) in some cases at the 

 blind end one or more special thick-walled cavities are formed 



(PARUTERINE ORGANS Or UTERINE CAPSULES), in which all or most of 



the eggs are collected, the uterus then undergoing atrophy. 



In species in which the uterus lacks an opening, simultaneously 

 with the growth of this organ an atrophy of the male apparatus, at 

 least of the testes and their excretory ducts, takes place ; this atrophy 

 also frequently occurs in the female glands, so that the entire mature 

 segments have besides the uterus only traces of the genitalia left. 



