1906.] WORMS OF THE THIRD TANGANYIKA EXPEDITION. 213 



found " swarming in great numbers rountl roots of water- weeds 

 in shallow water." It will be obvious in the course of the 

 following description that the worm is either i-ightly referi'ed to 

 this genus and subgenus or that it requires a new genus or 

 subgenus for its reception on account of certain peculiarities 

 which will be duly noted. 



A specimen which I have selected as the type (as regards 

 external characters) measured 38 mm. in length and consisted of 

 96 segments. The setce appear of considerable length in proportion 

 to the diameter of the body. They are of the usual shape, but 

 distinctly bifid at the tip, though it often happens that the upper 

 half of the cleft extremity is worn down and the seta thus appears 

 to be merely hooked. I believe that the existence of uncinate 

 setse is new to this particular group of Oligochfeta. 



The clitellum is not very extensive, occupying as it does 

 segments xiv.-xviii. and commencing or ending, as the case may 

 be, towards the middle of each of these segments. The clitellum 

 is saddle- shaped. The generative pores, the actual orifices, ai'e 

 not very plain on the mounted specimen. But from serial 

 sections I have ascertained that the spermathecal pores lie between 

 segments viii./ix. and the male pores upon segment xvii. ; the latter 

 nearly in line with the ventral setae, and the former near the lateral 

 setfe. It is to be noted that both setae of the ventral as well as 

 the dorsal pair are present upon segment xvii. and that they are 

 not in any way modified. The male pore on each side is just to the 

 outside of the pair of setae, and is borne upon a prominent flap 

 Avhich is not invaded by the clitellar epidermis. Its structure will 

 be dealt with later. 



The aUmentarff canal is without a gizzard. In the ixth seg- 

 ment the (lesophagus is provided with a ventral pouch, which 

 whether single or paired is so characteristic of the subfamily 

 Ocnerodrilinae. In the present species, however, this pouch, 

 which is single, is greatly reduced in size and bifurcates into two 

 after its emergence from the gut. Indeed, if it were much larger 

 there would be, in view of the large size of the spermathecae, 

 hardly room for it in the ixth segment. It is a smallish sac 

 lying ventrally to the oesophagus and narrowing at its junction 

 with the oesophagus very anteriorly in the ixth segment. It 

 has not a specially glandular appearance, and the lining epithelium 

 is merely folded. There is no such complicated folding as occurs, 

 for example, in Gorcliodrihbs. The ventral pouch of this species 

 appears to be either an incipient or a degenerating structure. A 

 largish blood-vessel is attached to the posterior end of each 

 bifurcation. The septal glands of the present species extend back 

 into the viith segment. 



The vascular system is noteworthy on account of the extreme 

 vascularity of the integument, which is ecpially obvious in the 

 specimen mounted entire and in sections. This was especially 

 plain in the anterioi- region of the body. If the capillaries do 

 not actually penetrate the epidermis, they only cease just below 



15* 



