1920.] J. Stephenson: Oligochaeta from India and E. Persia. 21] 



but, since there are no end-bladders as in P. sansibaricus, it is not always easy to see 

 where exactly they end, and in any case there is no regular alternation. 



It is difficult in some of the examples of this and the last few species to demon- 

 strate the testis sacs to complete satisfaction. Here they seem to be present in seg- 

 ment x, the mass of developing spermatozoa being covered over by a thin filmy mem- 

 brane ; the sacs of the two sides are probably continuous beneath the gut. In seg- 

 ment xi the testis sac is continuous on each side with the seminal vesicle. 



The seminal vesicles are in segments xi and xii ; they are large, taking up the 

 whole available space, with a granular surface but not otherwise lobed ; there is no 

 indication of separation dorsally, — the pair in each segment is completely fused. 



The prostates are large, and take up the whole of three segments, xvii to xix ; 

 ' they are deeply indented by the septa, and also otherwise much cut up. The duct is 

 moderately long, is bent with the angle directed backwards, is soft and rather thin in 

 its ental, thicker and shining in its ectal portion. 



The female organs have the usual situation. 



The spermathecae, in segments vii and viii, have each a large irregularly lobed 

 sac-like ampulla, which is as broad as long. The duct is stout, slightly shiny, well 

 marked off from the ampulla, about half as broad as the ampulla but considerably 

 longer, — i| times as long (fig. 13). The diverticulum appears as a rounded knob at 

 the ental end of the duct, with two small masses of iridescent spermatozoa shining 

 through. 



There are no penial setae. 



Re?narks : — The above is the description of the more mature of the two specimens 

 from Sitong Ridge. The specimen from Jor Pokhri differed slightly ; thus the papil- 

 lae bearing the male pores, and so the male pores themselves, were rather further 

 apart, — opposite setae d instead of c, and separated by perhaps one-seventh of the 

 circumference as against one-twelfth in the specimen described above ; the depression 

 containing the papillae was less marked ; and the spermathecal pores were wider 

 apart, — opposite setae d or e instead of the interval cd. 



The closest relative of the present form is certainly the species last described. 

 In this, the numbers of the setae are smaller, and the configuration of the male field 

 and the degree of separation of the male and spermathecal apertures also differ. The 

 most important points however are the spermathecae (the figures show the great 

 difference in the relative length of the duct), and the position of the last heart (in xii 

 here, in xiii in the last form). 



It is difficult, in cases such as this, where a number of related forms have appar- 

 ently arisen recently, or are possibly yet in process of differentiation, to know when 

 the degree of differentiation which justifies the creation of a new species has been 

 attained. Had this form been found at a distance from P. pokhrianus, its separation 

 as a different species might perhaps have been justifiable ; so far as the recollection 

 of my own experience goes, the position of the last heart does not, I believe, vary 

 within the limits of recognized species. (But see description of Octochaetus prashadi, 

 post. p. 233). 



