AND ZOOGEOGRAPHY OP INDIAN OLIGOCH^TA. 



135 



floor near the itestis, sometimes actually surrounding the 

 attachment of the testis as in Dravnda jajwnica. The vas 

 deferens leads off from the funnel, and descends on the septum 

 to the ventral body-wall (text-fig. 10). 



Text-fio'ure 10. 



rt.sac 



f udpr 



Testis sac of Brawida. References as before ; in addition, ]pr.. prostate."] , j 



(2) The Testis Sacs of the Moniligastrklce considered as 

 Segments. 



Leaving aside for the moment the Moniligastridse, it will be 

 seen from the above that throughout the Oligochaeta the testis is 

 morphologically on the posterior face of the anterior septum of 

 its segment, of the peritoneal covering of which it is a proli- 

 feration ; and the funnel faces it on the anterior face of the 

 posterior septum, of the peritoneal covering of which it is a 

 modification. On now comparing the figure which represents the 

 condition in the Moniligastridse (text-fig. 10) it is evident that 

 the most feasible explanation of the nature of the testis sacs of 

 this family is that which would regard them as the equivalent of 

 segments, of which the anterior and posterior walls have fused 

 together for the greater part of their extent. 



The cavity of the sacs cannot be a mere split in the septum, 

 since it is lined throughout with epithelium. Following the 

 usual rule, the cavity must be coelomic, and the epithelium 

 peritoneal epithelium. 



In Syngenodrilus, to which reference will again be made in tlie 

 sequel, there is given off' from the posterior .testis sac a seminal 

 vesicle (text-fig\ 16) in precisely the same way as the seminal 

 vesicle is given off from the testis segment in the more primitive 

 forms {cf. text-fig. 7). 



Again, we have seen in the foregoing article how, in the 

 genera Moniligaster and Dmivida, there is a tendency to shut oft' 

 the ovaries and their funnels in special chambers. These 

 chambers represent segment xi, and various stages in the gradual 

 limitation of the extent of this segment can be traced in actually 

 existing forms. The ovarian chamber contains the ovaries and 



