CESTODARIA 441 



the right, and just below the median isthmus of the ovary 

 dilates into the ootype (ootp), a large oval chamber which 

 receives the openings of the oviduct (opo), common vitelline 

 duct (ovit), and the large shell-gland (shgl). From the hind 

 end of the ootype arises the uterus (ut) as a slender convoluted 

 duct Avhich, lying dorsal to and to the left side of the median 

 isthmus of the ovary, passes forward and, immediately anterior 

 to the isthmus, turns to the right and commences its zigzag 

 course anteriorly, attaining its wide lumen at a short distance 

 in front of the ovary. The vagina and uterus thus form a com- 

 plete ' circuit ' with a common opening to the exterior anteriorly, 

 the proximal part or vagina serving for the inlet of the sperma- 

 tozoa and the distal part or uterus serving for the exit of the 

 fertilized eggs. In no other type of Cestode do these two ducts 

 have a common external opening. The ovary or germarium is 

 bipartite and of the form shown in PI. 24, fig. 2. The two 

 halves are united across the middle line by a transversely 

 elongated receptacle — the isthmus (PL 24, figs. 2, 8, lov)— 

 into each end of which open a number of fine ducts (odcts) 

 from one-half of the ovary. In all my mature specimens the 

 isthmus is full of eggs. At the anterior end of the uterine region 

 the mass of testes, divided into two posteriorly in the testicular 

 region by the median vas deferens, ends as two diverging 

 strands, one on each side of the anterior uterus. The marginal 

 strands of vitellaria lie, one on each side, to the outside of the 

 uterus. PI. 24, fig. 12, represents a transverse section through 

 the uterine region anteriorly, viewed from the hind aspect, in 

 which the uterus (ut, the median space containing two eggs) 

 is seen to be opening into the vagina (vag, the left extension of 

 the median space, both ducts having a common ventral opening 

 (the vagino-uterine pore, vuo) to the exterior. This transverse 

 section also shows the hind strands of the testicular mass (tes), 

 the vitellaria (vit) external to these, the two main longitudinal 

 nerve-strands (n), the thick cuticle and subcuticula, the single 

 outer well-defined zone of longitudinal muscle-fibres (lmus), 

 and the inconspicuous lateral dorso-ventral fibres. 



The post-ovarian region — a region which is very short in 



