1901.] FBOM BBITISH EAST AFRICA. 337 



seventeentli and eighteenth segments is occupied by an exceedingly 

 prominent sucker-like structure ; this does not stray beyond the 

 limits of the two segments mentioned. Its outline is that of a 

 rounded square, and the walls A\hich surround the central depres- 

 sion ai'e well marked. In Pohjioreutus finni each pore, both the male 

 and the female, has a similar wall surrounding it. In the present 

 species the two seem to have as it were fused together — a state of 

 affairs which is not in the least due to a greater contraction of the 

 worm, since the clitellar region was not at all contracted. The 

 actual orifices within this area I could not detect, and did not wish 

 to injure the specimen by an exploratiou. I imagine, however. 



Text-fig. 83. 



Clitellar region of Polytoreutus hinclei. X 4. 



that the male pore is on segment xvii., a very general position, 

 and that the pore of the spermathecal sac is either on xviii. or 

 just on the vei'ge of xix., i. e. that it is placed intersegmentally 

 between segments xviii./xix., also a very general position. . This 

 sucker is exceedingly conspicuous, and can be readily seen to bulge 

 ventrally on a lateral view of the worm. It is important to notice 

 that it appears to be fully matured before the clitellum. Tor in 

 the second specimen, which is only a little more than half the size 

 of that which I have made the type of the new species, there is 

 no trace of a clitellum, but the generative area is quite as well 

 developed. The clitellum of Polytonutus Jiindei occupies seg- 

 ments xiii.-xviii. and is developed all round the body. 



Behind the clitellum the next four segments, i. e. xix.-xxii., show 

 a ventral thickening such as occurs in PolytoreMtus gregorianus and 



