OCR Text |
Show 1901.] FROM BRITISH EAST AFRICA. 337 seventeenth 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 tbe walls which surround the central depression are well marked. In Polytoreutus 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 tbe 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 exploration. I imagine, however, Text-fig. 83. Clitellar region of Polytoreutus hindei. 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 verge of xix., i. e. that it is placed intersegmental]} 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. For iu 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 Polytoreutus hindei occupies segments 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 Polytoreutus gregorianus and |