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Show 1906.] WORMS OF THE THIRD TANGANYIKA EXPEDITION. 211 nearly ripe ova are not all to be found at or near the free edge of that gonad. I noted cells far on the way to become ripe ova at some distance in the interior of the gonad, and in front of these was a thick layer of germinal cells not far advanced along the same road. The oviducts, as in Eudriloides also, open freely into the cavity of the xiiith segment. This, however, is a character also shared by Platydrilus. But the present genus (if it be rightly elevated to distinct generic rank) does not show the connection between the oviduct and the spermathecal sac which exists in Platydrilus*. The oviducal funnel is very extensive, more so than in a large number of Oligochaeta. The upper lip is very long, extending dorsally into actual contact with the dorsal blood-vessel as it traverses the septum. The lower lip of the funnel is pushed into and, as it were, tucked away into the receptaculum ovorum, which lies on the opposite side of the septum in segment xiv. The oviduct itself, instead of running a straight course to the oviducal pore in the xivth segment, projects forward into the cavity of segment xiii. as a loop enclosed in a continuous muscular sheath. This U-shaped region of the oviduct differs in no way in structure from the rest of the tube, which runs an approximately straight course. The oviduct, therefore, is like the sperm-duct of certain Eudrilids (e. g., Stuhlmannia), in that it passes through the septum xiii./xiv. and, instead of opening into segment xiii. and facing forwards, turns back and for the most part at least faces back again into segment xiv. W e have, however, to consider the long tract of cubical epithelium which lies along the anterior face of septum xiii./xiv., extending up to the level of the dorsal vessel. That this is continuous with the actual indipping of the funnel of the oviduct is without doubt. At the same time it seems possible to compare this tract of epithelium with the egg-conducting apparatus of other Eudrilids. It represents, as I think, potentially part of the egg-conducting apparatus (the so-called spermatheca) of Eudrilus t. I have lately shown that the large sacs in that genus are a development of the septum dividing-segments xiii./xiv., and that primitively the epithelium of the oviducal funnel is continuous with a layer of equally cubical epithelium which with the muscular wall behind it is evaginated into the xivth segment to form the sac in question. In early stages such as I studied it is not possible to draw a distinct line between oviducal funnel and the epithelium of this sac. An earlier stage still (which I did not find in Eudrilus) would be, I should imagine, a continuation of the epithelium over the septum without a trace of the evagination. This state of affairs is precisely what we have in the Eudrilid which forms the subject of the present remarks. I do not think, however, that it is a temporary stage, and that the ultimate product would be a sac or sacs like those of Eudrilus, and for the following reasons:- * Here I confirm Michaelsen, who queries the fact. f " The Gonad of Eudrilus;' P. Z. S. 1902, vol. ii. p. 89. PROC. ZOOL. Soc-1906, VOL. I. No. XV. 15 |