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Show 822 MR. F. E. BEDDARD ON [Nov. 3, § Nephridia. Hardly anything is known about the nephridia in the genus Acanthodrilus. Perrier does not refer to their presence in his description either of the genus1 or of the three species examined by him. A statement that the apertures of these glands are placed above the ventral pair of setae 2 implies, however, their existence. Dr. Horst ' failed to find any nephridia at all in A. schlegelii; and in A. buttiko-ferii they appear to be represented solely by a tufted organ in the anterior part of the body, attached to the pharynx, which is probably identical with the "salivary" gland of A. multiporus, to which I have already referred. They are present in A. kerguelenensis and in A. capensis. In all the three species described in tbe present communication nephridia are found ; in A. multiporus I have already 4 described the structure and distribution of the nephridia. This species is apparently unique among Earthworms in possessing a single nephridium to each of the eight setse, the duct of which opens in close proximity to the seta by a single orifice in the posterior part of the body ; in the anterior part of the body the duct of each nephridium branches and opens by a multitude of orifices. A. nova zelandia and A. dissimilis, the nephridia are remarkable in that they alternate in position from segment to segment of the body. It is a general rule among Earthworms, possessing only a single pair of nephridia in each segment of the body, that the position of the external apertures of these is constant. In Lumbricus the nephridia are related to the ventral pair of setse, near to which they open, and the same is the case with Eudrilus and several other genera. Perrier discovered that in other genera (e. g. Phinodrilus) the nephridia bore a similar relation to the dorsal pair of setse or to one of these setse. if the two had become separated, as is so often the case. These facts led M. Perrier to support Prof. Lankester's hypothesis of the typical presence of two series of nephridia in Earthworms corresponding to the two series of pairs of setse. The characters of the genus Plute/lus appeared to be entirely confirmatory of this hypothesis. In this Earthworm the setse are disposed in eight longitudinal rows of a single seta each, and the external orifices of the nephridia alternate in position from segment to segment, sometimes being situated near to one of the two dorsal setae, sometimes near to one of the ventral setse. I have elsewhere pointed out that these facts really indicate the partial persistence of four series of nephridia5 corresponding to the four rows of setse, and entered to some extent into the questions raised by Prof. Lankester's hypothesis, so that I need not recall the matter. In A. nova zelandia and dissimilis, where, as has already been 1 Nouv. Arch. &c. p. 85. 2 Loc. cit. p. 162. 3 Notes from Leyden Museum, vol. vi. pp. 105, 107. 4 Proc. Roy. Soc. no. 238, 1885, p. 459. See also a forthcoming paper in Ann. Sci. Nat. ° v l 5 Proc. Roy. Soc. loc. cit. |