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Show 1901.] AND ARRANGEMENT OF EARTHWORMS. 197 annulation. The fourth and fifth segments are each divided into two by a median furrow; the sixth is triannulate ; the fact that the setae occur in the middle ring of this segment, and on the anterior of the two which are biannulate, shows that it is the anterior annulus which is further subdivided. The three following segments have each four annuli, the setae being implanted upon the second ring. Segments x., xi., xii. are again triannulate. After the clitellum the segments are more or less distinctly triannulate for a considerable distance back. The above description is drawn up from the specimen which I have regarded as the type ; but the others show no differences save for incomplete additional furrows upon some of the segments. The prostomium is broad, and does not at all impinge upon the first segment of the body. But a pair of furrows upon the first segment make with it a T-shaped piece. There are naturally 8 setce per segment, arranged in couples. The two couples of each side are close to each other and are quite ventral in position. The two setae of the ventral couples are distinctly closer together than are those of the lateral couples. I found the lateral as well as the ventral setae upon the clitellar segments ; and setae do not appear to be wanting upon the second segment of the body. It is not, however, easy to see them, since this segment, like the first, is marked by a number of short longitudinal furrows 1. The clitellum of this species of Typhoeus, like that of others, occupies segments xiii.-xvii. Dorsal pores are obvious after the clitellum, but seem to commence anteriorly to that part of the body. As is the case with the majority of the already known species of the genus Typhoeus, T. nicholsoni possesses genital papillce. There is a pair of these papillae upon all of the three specimens in m y possession, which are of a rather peculiar form. The area occupied by the papilla is, according to the state of contraction of the body, circular or more elliptical, the long axis of the ellip.-e being at right angles to the long axis of the body. A complete furrow separates the two papillae from the surrounding integument, and they are separated from each other by a furrow. Their general appearance and relations can be gathered from an inspection of the accompanying drawing (text-fig. 54), which illustrates the ventral surface of this worm. The two papilla? occupy nearly the entire space between the ventral setae of segments xv. and xvi. Laterally they extend for a very short way outside of the area thus defined. Each papilla has a central circular patch of different appearance from the peripheral part. The spermathecal pores lie between segments vii./viii., and are very closely approximated ventrally ; their orifices correspond in position to that of the innermost seta of the ventral couple. The male pores are extremely conspicuous. They lie upon the 1 This may possibly account for my failure to find them in T. gammii. PROC. ZOOL. Soc-1901, VOL. I. No. XIV. 14 |