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Show 216 MR. F. E. BEDDARD ON THE OLIGOCH.ETE [Mar. 6, give of its external and internal organisation. There will be equally no doubt from the facts which I shall relate that this Tanganyika worm is specifically distinct from A. p>ordagei. Alluroides tanganyikce is a more purely aquatic species than the type species of the genus; for it was dredged from about ten fathoms of water, whereas A. pordagei was found in the m u d of a swamp. So far as I a m aware, nothing further has been discovered about this genus since the publication of m y own paper referred to above*. Dr. Michaelsen has, howevert, from a consideration of the facts made known by me, placed the genus in a separate family, Alluroididae. The new species to be described here necessitates no alterations in the family characters as given by Michaelsen, and a very slight change in the generic characters, which will be attended to after the description of Alluroides tanganyikce. This species is a small, slender, rather transparent worm, suggestive of a Lumbriculid, and, so far as I can recollect the latter, not very different in size from Alluroides pordagei. The single specimen is about 30 m m . long and not more than 1*5 m m . broad in the widest part of the body (anteriorly). It consists of 60 segments. The thinness and transparency of the worm, when viewed as a microscopic object, is distinctly that of a Limicolous Oligochaete. The prostomium is rather long and pointed ; it is divided by a constriction into an anterior and posterior half. It is longer than the first segment of the body, but is hardly to be separated from it dorsally. The first-marked constriction on the body separates the first two segments from each other. The setce are plain and of the ordinary pattern without a cleft extremity. They are strictly paired and present upon all the segments of the body with the exception of the first and that which bears the male pores, where the ventral pair are absent. The boundaries of the clitellum were not distinguishable. There is no external penis, but the partial immaturity of the specimen may be the cause of this. I only use it doubtfully therefore as a specific character. It is mainly by reason of the position of the generative apertures that I place this species unhesitatingly in the genus Alluroides. The most anterior of these is a single widish aperture upon the boundary-line of segments viii./ix. The worm is sufficiently transparent to allow it to be seen that this orifice is continuous with a closed thick-walled sac, which seems to m e to be obviously the spermatheca. The main fact to be considered about the spermathecal pore is that it is single and dorsal median in position. I believe that this state of affairs is unique. W e find, however, frequent cases of the coalescence of two ventral pores to form one medianly situate ventral pore and a further coalescence of two spermathecae, or, it may be, the disappearance of one. In comparing * See also 'A Monograph of the Order Oligochaeta ' (Oxford, 1895), p. 224. t Oligochaeta in 'Das Thierreich ' (Berlin, 1900), p. 106. |