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Show 170 MR. F. E. BEDDARD ON A LARGE EARTHWORM. [Mar. 16, area are bounded by the ventral pair of setae; this area, which distinguished by its very pale colour, surrounds the male genital apertures, which are upon the 17th and 19th segments respectively (see fig. 2). In A. ungulatus the clitellum extends from 14-17 inclusive and the male genital apertures are upon the 18th and 20th segments ; in A. obtusus the clitellum is unknown, the male genital pores are upon the 19th and 21st segments. Dorsal pores are stated by Perrier to be present in his two species ; in m y species they are present and commence apparently at the 13th or 14th segment ; in one specimen the first dorsal pore was visible between the 12th and 13th segments, in a second specimen this pore was a segment further back. I have figured these apertures as extending over the clitellum, since they were visible on these segments in immature examples without a clitellum ; when the clitellum was present they were apparently absent or, rather, perhaps rendered invisible by the swollen glandular integument. In Acanthodrilus multiporus (see P. Z. S. 1885, pt. iv. p. 810) I observed dorsal pores commencing after the clitellum, the first pore marking the posterior boundary of that region of the integument. In Acanthodrilus dissimilis and A. nova zelandice they appear to be present though very inconspicuous ; I only noted them after the clitellum. In the furrows separating segments 7-8 and 8-9 were a pair of distinct rounded apertures corresponding to the inferior pairs of setas ; these are the apertures of the copulatory pouches. The pair of setae on segment 8 were in most instances greatly modified, being much larger and more conspicuous than the other setas of the body ; their appearance is very like that of the genital setae on segments 17 and 19. In describing the structure of the genital organs I shall call attention to those setae which correspond to internal structures entirely novel in this genus. The ordinary setae of the body are distributed in pairs as in other species of the genus. The apertures of the nephridia are very conspicuous and correspond in every case to the more dorsal pair of setas. The female generative pores are displayed in fig. 2 ; they are a pair of very minute pores situated on the 14th segment in front of and to the inside of the ventral pair of setae ; their position is nearly similar to the corresponding pores of A. nova zelandice ; they are on the same segment as in that species, where, however, the pores are placed in front of the outermost of the two ventral setae. In Acanthodrilus capensis I find the female generative pores are upon the 14th segment and the ovaries in the 13th segment, and not, as erroneously stated in my paper on that species 1, in the segment anterior to these ; in the present species, however, the pores are placed in front of the innermost of the two ventral setae. Vascular System.-In fig. 7 of Plate XIX. is illustrated the main vascular trunks of the anterior region of the body. The dorsal vessel 1 Proc. Eoy. Phys. Soc. 1885-6, p. 369. |
