26 ZOOLOGICAL EESULTS OF THE ETJWENZORI EXPEDITION. 



either side, and independent, of the penis The present species, the exact locality 

 of which within this area I fix by means of its specific name, is represented by a fully 

 mature example which measures 77 mm. in length by 5-6 mm. in breadth. It is 

 therefore a rather stout and comparatively short worm. 



The setce of Polytoreutus ruwenzorii are disposed like those of other species of the 

 genus : i. e. the ventral setse are much wider apart than the lateral setee. The distance 

 between each seta of the ventral pair is something like three times that which separates 

 the individual setse of the lateral pair. I have endeavoured to make an exact study of 

 the distribution of the setse upon the clitellar segments, concerning which there is 

 some but not exhaustive information, on some other species of the genus already 

 described ; for this character seems to be one of probably systematic value. On these 

 segments I could only find one of the two setee of the lateral pair, and the seta present 

 was the innermost. I ought to mention that these statements depend upon a micro- 

 scopic examination of the entire cuticle stripped from the body, and not merely upon 

 an inspection of the entire worm with a lens. The apertures through which the setse 

 are protruded are so obvious that the failure to find one is strong evidence of its 

 absence. The ventral setse, on the other hand, were present upon the clitellar segments 

 with the exception of the xviith, where only the outer seta of the pair was present. 

 Ventrally the clitellum is not so strongly developed as it is laterally and dorsally, 

 which facts may be related to the presence or absence of setse. 



The cUtelhim of Polytoreutus ruwenzorii is, like that of Polytoreutus sylvestris and 

 some, but not all, other species, best developed laterally and dorsally. Ventrally it is 

 not so Avell-developed, and here the intersegmental furrows are plainer than they are 

 laterally. It embraces segments xiii. toxvii., which is the usual extent of the clitellum 

 in this genus. 



The nephridiopores lie in front of the lateral pair of setse, in front of each pair, but 

 not definitely opposite either of the pair. They commence apparently in the fourth 

 segment. A notable fact with reference to these pores is that when the cuticle is 

 stripped off" — and I have mapped the pores by this means — a considerable strip of 

 the (as it would therefore appear) chitinous lining of the duct of the nephridium is also 

 stripped off" and protrudes from each aperture. I have not noticed anything of this 

 kind in other Oligochseta. 



The oviducal pores are quite conspicuous and lie upon the xivth segment behind and 

 to the outside of the nephridial row and the lateral seta of that segment. The single 

 male pore is on the border of segments xvii./xviii. and the spermathecal pore behind 

 it upon the interval xviii./xix. 



The internal anatomy of this species, so far as concerns the alimentary and 

 circulatory organs, seems to agree with that of the next species to be described and 

 with the members of this genus generally. 



The sperm-sacs are like those of Polytoreutus generally (but not P. bettonianus) in 



