184 Transactions. 



The six testes on each side are connected by short vasa 

 efferentia with a dorsally situated vas deferens, which runs 

 forwards into segment xiii and then bends backwards along the 

 floor of the body in a very undulating course, to somite xvi ; 

 here each vas deferens opens into the seminal vesicle of its 

 side. 



The vasa efferentia open by ciliated funnels into the testes 

 through the anterior wall, except in the last, where the funnel 

 perforates the posterior wall. 



The seminal vesicle may be regarded essentially as a cylin- 

 drical sac, but as it passes forwards it is much constricted 

 and folded by the enteric caeca and by the vertical muscles, so 

 that in reality its outline is very complex. It commences in 

 somite xvi and passes forwards into somite xii, where it com- 

 municates with the narrow, muscular-walled ductus ejacula- 

 torius. This is cylindrical, a good deal coiled in somite xi, and 

 opens mesially into a pyriform or subspherical glandular sac, 

 which may be termed " the spermatophoral sac " ; it is trans- 

 versely placed and opens with its fellow into a shallow, broad, 

 common atrium, which in its turn communicates with the 

 exterior between somites xi and xii. 



Whitman (19) has described and figured the spermatophores 

 of Placohddla parasitica {Clepsine plana), and discussed the 

 question of the " hypodermic impregnation," giving an account 

 of the structure of the different regions of the sperm-duct, with 

 which account the present species closely agrees. 



The ductus ejaculatorius, when it issues first from the se- 

 minal vesicle, is lined by a low epithelium ; further along this 

 l)ecomes a layer of high glandular cells, which reduce the lumen 

 of the tube. 



In the " pyriform sac," in which Whitman believes the 

 «permatophore is formed, the epithelium becomes still taller, and 

 the lumen almost obliterated ; the cells are much vacuolated in 

 the specimen under consideration. 



The seminal vesicle is distended with spermatozoa ; the wall 

 consists of a thin connective-tissue coat (staining blue in picroni- 

 grosin) lined with a low columnar, almost cubical, epithelium. 



In segment xviii, on the left side of the body, situated just 

 "below the sixth enteric caecum, is a mass of spermatozoa, not 

 enclosed by any wall, but free in the body cavity : this mass 

 is quite isolated from the seminal vesicle and from the testicular 

 sac. It has, no doubt, arrived here by migration from the 

 surface, as suggested by Wliitman ; and, in addition, I note 

 a smaller mass dorsally above the gut. 



The ovary (or ovarian sac) is a comparatively small lobulated 

 sac, of short extent, occupying only two segments, xiii and xiv ; 



