540 ORESSWELL SHEAEEK. 



support this conclusion." Thus, while the nephridia project 

 into the space of the body-cavity, the modified nephridia of 

 this seg-raent (the fifth pair of the female) open into the 

 cavity of the testis. However, it seems to me there are 

 many difficulties in the way of accepting this origin of the 

 seminal vesicles. 



I have already called attention to the closed nature of the 

 spaces of the testis tissue and the fact that they are entirely 

 separated from the primary body-cavity about the gut 

 (fig. 4, s. 2)- 111- and fig. 11, m. v.), and Dinophilus would 

 seem to be one of the few animals in which both the primary 

 and secondary body-cavity exist alongside of one another at 

 the same time. Repiachoff (21) at some leugth has con- 

 sidered the relationships of these two cavities in Dino- 

 philus, and has clearly pointed out how the secondary body- 

 cavity of Annelids is probably represented in Dinophilus 

 by the spaces in the testis tissue. These towards the poste- 

 rior end of this structure fuse together to forui the large and 

 roomy cavity of considerable size well shown in Schimke- 

 witsch's fig. 43 6 (23). It is lined by a definite epithelium^ 

 while the primary body-cavity about the gut possesses no 

 such lining membrane.^ As the nephridia in Dinophilus 

 are related to the primary body-cavity alone it is necessary 

 to suppose on the basis of Harmer's theory that those of the 

 fifth segment have lost their connection with this structure, 

 and acquired openings into the testis cavity. I have also 

 shown that the nephridia do not open into the primary body- 

 cavity, but are closed ; therefore the funnel-like openings of 

 the vesiculae seminales are new structures that have been 

 developed since this relationship has been established, and 

 cannot have been transferred, as Harmer thought, from the 

 primary body-cavity. 



The resemblance of the male reproductive system of Dino- 

 philus to that of the Turbellaria is so similar in many 

 respects, although the reproductive system in these forms is 



' Repiachoff (21) lias described a peritoneal lining to tiie outer wall of the 

 gut in 1). gyrociliatus, but no such lining is present in D. taeuiatus. 



