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Show 826 MR. F. E. BEDDARD ON [Nov. 3, Megascolex, and which undoubtedly occurs in other Earthworms, coupled with their absolute independence of the vas-deferens funnels, is, I think, sufficient to show that m y determination is correct. The vasa deferentia, instead of uniting to form a single tube, as appears to be the case in the majority of Earthworms, remain obviously distinct from each other for the whole of their course ; they pass down close to the ventral pair of setse, but to the outside of them, and in certain regions, at any rate, are not very firmly fixed to the body-wall ; their walls are supplied with abundant blood-capillaries. On referring to Perrier's description of the anatomy of Acanthodrilus, I find that he figures the vasa deferentia in A. ungulatus * as being composed of two widely separated tubes. The prostate glands are two pairs, each connected with one of the four male genital apertures ; each consists of a thick-walled glandular tube variously coiled upon itself, and terminating in a narrow muscular duct which has a nacreous glitter. In A. multiporus (PI. L I U . fig. 2) the mesenteries in the neighbourhood of the pro-stales are arranged in a somewhat radiating fashion as bands of nacreous-looking fibres, which are attached at one extremity to the ventral body-wall, close to the apertures of the prostate ; they perhaps serve as special " cremaster " muscles. With each of the male generative apertures is connected a thin-walled muscular sac containing a number of long penial setse, hooked at their extremity, but not ornamented in the way that is often found in Acanthodrilus. There is therefore nothing remarkable in the male generative system of this species, except in the fact that the apertures are situated within the clitellum instead of behind it; it is, with the exception of this relation of its aperture to the clitellum, precisely similar to the male generative system of other Acanthodrili, even to the numbers of the segments on which the vasa deferentia open. If systematists are unwilling to include this species within the genus Acanthodrilus, it cannot, at any rate, be placed far from it, certainly not in a distinct group. In describing the external characters of these worms, it should have been mentioned that the male apertures are situated upon the summits of conspicuous papillae ; transverse sections through this region of the body-wall show that the papillae are the result of the more elongated form of the epidermic cell surrounding the apertures of the generative ducts ; the cells which cover the papillse are from three to four times the length of the cells that are found elsewhere, but are similar to them in their structural characters. In A. dissimilis the duct of the prostate gland comes into close relation with the genital setso ; the latter are of course homologous with the ordinary locomotor setse, and simply replace them upon the genital segments. Each of the two genital setse corresponding to each genital aperture is contained in a separate sac, which is lined by a continuation of the epidermis, and communicates with the exterior by a separate orifice. There are of course numerous accessory setse, which 1 Loc. cit. pi. ii. fig. 18. |