208 



MR. F. E. BEDDARB ON A 



the vas deferens on the ventral side. At first the vagina is wide, 

 with a much plicated lining epithelium suiTOunded by a thick 

 layer of muscles. It then suddenly becomes much narrower — 

 these two regions of the vagina being thus analogous to the wider 

 distal sac-like part of the cirrus and the narrow proximal part 

 of the same. The narrow region of the vagina joins the wider 

 region at an angle. Followed back the narrow part of the vagina 

 dilates with moderate abruptness into the large receptaculum 

 seminis, which commences at a point about on a level with the 

 pore side of the large ventral water vascular vessel. 



Text-fig. 28. 



Sagittal section showing different position of cirrus (C.) and vagina (F.) in 

 two segments of Otiditmnia ewpodotidis . 



The Gi7'rus sac among the Tetracotylea occurs in at least two 

 types of structure. One, the most general, is typified, for example, 

 by that seen in Siilesia and represented in a figure in Dr. Gough's 

 paper upon that genus and Avitellina, and discussed in a footnote 

 concerning the cloaca genitalis. The second type, which is cer- 

 tainly not so general, is seen in a genus Anoplotcenia, the anatomy 



