1901.] AlfD AERATfaEMENT OP EARTHWOEMS. 189 



space lying between the ventralmost seta of each side. The lateral 

 setae are so closely approxiiaated that they are not more than j of 

 a millimetre from each other. The distance of the lateral pair 

 from the outermost seta of the A^eutral pair is about equal to that 

 of the ventral median space. The dorsal median space measures 

 11 mm. The total circumference of the worm is thus about 27 mm. 

 At the tail end of the body the space between the setse of the ventral 

 pair retains its width until the very extremity when it is narrowed. 

 This, however, is simply a matter of the diminished calibre of the 

 body; there is no proportional decrease in the interval. I could find 

 no dorsal pores, which structures appear to be absent in the family 

 Eudrilidce. 



The nepliridiojpores are very obvious and lie in front of the lateral 

 setse. 



The ditellum occupies segments xiii.-xviii. and is completely 

 developed all round the body. 



Dotted over the segments, and often forming continuous lines 

 with the setsB suggestive of a perichsetous condition, are the 

 numerous integumental sense-organs, well known to occur in this 

 genus. 



In my Monograph of the Oligochfeta the position of the external 

 generative apertures is accidentally reversed. In Polytoreutas 

 gregorianus, as in all the other species of the genus, the male pore 

 lies in front of the spermathecal pore. 



The mcdepore (see text-fig. 50, p. 188) is placed accurately between 

 segments xvii./xviii. It is transversely oval, indeed slit-like, and 

 lies at the summit of a protuberance which occupies the middle 

 part of segments xvii. & xviii. between the ventralmost set?e. On 

 the xviiith segment this protuberance appeared to bear two faintly 

 marked papillae, one on either side. 



The spermailieccd pore is on the xixth segment, quite in the 

 middle of that segment ; it is rather a larger orifice than the male 

 pore. 



I append for the purposes of comparison drawings (text- 

 figs. 51, 52, p. 190) of the external characters of the two species 

 Polyforeutus Jdlindinensis and P.finni. Of neither of these species 

 have the external characters been at present figured \ though 

 their internal structure has been dealt with by myself". Figures 

 of the external characters of the genus Poly tor eutus are at present 

 limited to a figure of P. magilensis ^. 



It will be noticed that while P. kiUndinensis entirely agrees with 

 P. gregorianus in the position of the male pore and of the sperma- 

 thecal orifice, P.finni differs in that the male pore is very distinctly 

 in the middle of the xviith segment, and the spermathecal pore is 

 situated on the boundary line of the xviiith and xixth. 



It will be observed from the accompanying sketch (text-fig. 51) 



^ Save for a quite rough sketch of P. finni. 



^ " OligochiBta of Tropical Eastern Africa," Quart. Journ. Micr. Sc. vol. xxxvi. 

 p. 236. 



■^ " Some new Species &c. of Earthworms," ibid. vol. xxxiv. 



