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Show 692 MR. F. E. BEDDARD ON N E W [Dec. 20, habit which might perhaps discount the value of the characters afforded by the clitellar epithelium. Although the clitellar epithelium is only one cell thick, it is made up of cells of two kinds: there are large non-staining cells, imbedded among smaller cells loaded with darkly staining granules. Plate XLV. fig. 5 illustrates the structure of the clitellum, which, as will be seen, is not very much thicker than the epidermic tissue of adjacent segments not nodified. The setae, as in other species, are strictly paired; I could find no setae upon the second segment of the body: I have already mentioned that in M. barwelli these setae are very small and easy to be overlooked ; I could not find the least trace of them in the present species. The muscular layers of the body-wall are remarkable in certain points. The circular layer, as is shown in fig. 5, does not extend quite up to the longitudinal layer : between the two is a space occupied by a delicate connective tissue with interspersed nuclei; in this layer run the nerves, of which there are three main trunks in each segment. The muscle-fibres, when seen in transverse section, show the characteristic appearance of the muscular fibres of the Leech in a more distinct way than I have ever noticed in any Oligochaetous worm : the layer of muscular substance in each fibre is very narrow as compared to the central cavity, which is filled by a faintly granular matter; this is not stained ; the fibres differ greatly in diameter, the smaller ones being nearest to the epidermis. One might perhaps speak of the layer which lies between the circular and longitudinal muscles as a " nervous layer " ; it contains many small nerve-twigs besides the main trunks already referred to. The longitudinal muscular layer is, comparatively speaking, narrow; its fibres tend to be arranged in the bipinnate fashion which is so common, though not universal, among the higher Oligochaeta. Here also it was easy to see that each fibre has a central soft core. On the whole the structure of the body-wall of tbe Annelid, with the exception of course of the clitellum, is like that of Earthworms rather than the aquatic genera ; but Phreoryctes, which Claparede ranged among his " Limicolse," has a body-wall which is also like that of the higher Oligochaeta ; so that this point of resemblance is not conclusive as to the affinities of Moniligaster. Internal Anatomy. The internal structure of this new species of Moniligaster is not widely different from that of Moniligaster barwelli; there are four thickened septa which divide segments v./ix. Probably the existence of this number of septa is a character of generic importance, as they seem to occur in M. beddardi as well as in the two species referred to. The alimentary canal, again, presents no differences from that of other species ; there are no calciferous glands, and there appears to be no vascular tract of the oesophagus which in so many Oligochaeta replaces functionally these glands; the usual three gizzards are present, commencing in the xiiith segment. The nephridia have a large caecum as in other species; I observed the |