OCR Text |
Show 1906.] WORMS OF THE THIRD TANGANYIKA EXPEDITION. 217 the present species with Alluroides p>ordagei we find that an analogous concrescence would appear to have taken place dorsally; for in that species the paired spermathecal orifices are placed close together and well to the dorsal side of the lateral setae. The o . .. spermathecal pore has a tumid periphery and is very conspicuous. The mcde pores are upon segment xiii. and upon the ventral surface of the body. They are in line with the ventral setae, which are, however, absent upon that segment. These pores also are large and conspicuous. It will be observed that their position differs from that of the corresponding pores in Alluroides pordagei, which correspond to the lateral setae and not to the ventral. Concerning the oviducal pores I a m unable to be certain, as I could not distinguish the oviducts themselves. I think, however, that I have detected them lying behind the male pores and in line with them upon the boundary-line of segments xiii./xiv. The alimentary caned of this Annelid was plainly distinguishable throughout its course. I could see no gizzard, but septal glands were obvious. The oesophagus in the ninth segment acquires a coating of brown pigmented cells, which continue to the end of the body. From the ninth segment to the eighteenth inclusive the uesophagus is moniliform. From the nineteenth segment it is less so and somewhat wider. This region I regard as intestine. The transition from one region to the other is abrupt. The vascular system appears to m e to be arranged on the simpler plan characteristic of the aquatic families of Oligochaeta. The dorsal, which is the larger, and the ventral vessels are connected by a pair of looped vessels, quite as in e. g. the Tubificidae. Anteriorly I am unable to say anything about its relations, except that I could not trace the dorsal vessel forward beyond the large intestine and was quite unable to detect the nephridia. The spermatheca is an oval sac which reaches back quite to the end of the ninth segment. The atria end posteriorly in oval expansions looking very like spermathecae. There are naturally two of them. They are directed posteriorly to the pores upon the xiiith segment. In view of the facts brought forward here upon this new species of Alluroides, I venture to amend slightly the generic definition of Michaelsen and to distinguish the two species as follows:- Genus ALLUROIDES Beddard. Alluroides Beddard, Quart. Journ. Micr. Sci. vol. xxxvi. (n. s.) p. 252. Small, slender, aquatic or semiaquatic Oligochceta with simple S-shaped setce arranged in four pairs. Clitellum in neighbourhood of male pores. Alimentary canal without gizzard or glands. Meganephric with paired nephridia. Spermathecce (or spermatheca) without diverticula opening between viii./ix. at or near median dorsal line. Male pores on segment xiii. more or less ventral in position. |