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Show 814 MR. F. E. BEDDARD ON [Nov. 3, in the anterior part of the body there are a larger number of pores, forming a continuous ring round the body and between the setse. The dorsal blood-vessel is formed of two tubes which remain distinct throughout the body. The pharynx is provided with a large gland consisting of metamorphosed nephridia ; this opens into the buccal cavity by a long duct. The intestine has no cseca or glands. The above descriptions contain the main specific characters of these species. I shall now proceed to review their external and structural characters in greater detail, comparing them with each other, with other species of the genus, and with other genera. PART II. § Lntegument. Under this head will be discussed the external characters of the genus Acanthodrilus, as well as the structure of the integument. Clitellum.-In the specific definition it has been already stated that the clitellum occupies in all the three species under consideration eight segments, from the 12th to the 19th inclusive. In other species the extent of this modified region of the integument appears to be different. In A. uvgulatus it only occupies four segments, from the 14th to the 17th; A. bitttikoferi, on the other hand, has a clitellum which is only one segment short of A. multiporus &c, reaching as it does from the 13th to the 19th segment. M. Perrier, as is well known, has divided Earthworms into three great groups, characterized by the different relations borne by the male generative apertures to the clitellum : in the Preclitellians the male generative pores are placed in front of the clitellum, in the Intra-clhellians within it, and in the Postclitelliins behind it. Now, in all the three species of Acanthodrilus described in the present paper, as well as in one species (A. schlegelii) described by Dr. Hoist, the male generative apertures are placed within the clitellum ; M . Perrier's location of the genus Acanthodrilus within the group of Post-clitellians depends upon the examination of a single species referred to above, viz. A. ungulatus. As M . Perrier's classification in this instance at least separates species so closely allied as A. ungulatus and A. schlegelii, or any of the species defined in the present paper, it is evidently based upon characters which are not of final importance. W e are at present acquainted with so very few Earthworms, comparatively speaking, that the time has hardly arrived for a systematic arrangement of the whole group. It seems to me, however, that if any primary division is possible at all, it should be between the Preclitellian group on the one hand and the Intra- and Postclitellian on the other. The two latter have a good many characters in common which are not shared by Lumbricus ; as instances may be mentioned the general presence of prostates, the position of the gizzard, strung on to the oesophagus, instead of being placed at its posterior extremity, the position of the testes and spermathecse in |