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Show 1896.] FROM THE SANDWICn ISLANDS. 199 constant up to the end of the body. The formulal will read thus:- Segment I. V. XII. XVI. No. of seta3 .... 23 31 43 46 but on some segments quite close to the tail I counted as many as 49 setae. The size of the setae varies on different segments and on different parts of the same segment. The setae on either side of the nerve-cord, as is the case with other species (e. g. Perichceta houlleti), are larger than those more laterally placed. This difference commences to be well marked in the third setigerous segment, anterior to which, it may be observed, is no ventral nerve-cord, but the circumcesophageal commissures. Erom the third setigerous segment to the sixth (inclusive) there is this marked difference between a few ventral setae-particularly the ventral-most seta-on either side of the nerve-cord and the rest of the setae of the segment. On the tenth segment all the setae are very much smaller than on the preceding segments 2, and those on either side of the ventral nerve-cord are not larger. On the eleventh segment the setae again are larger, and there is a slight difference in size between the ventrahnost two or three setae and the rest, but not nearly so marked as on segments iv.-vii. The clitellum is, as has been already mentioned, entirely witnout setae ; but no doubt in the immature worm they are present. In any case the special longitudinal muscles of the setae were quite obvious in the mature worm. At the hinder end of the body the setae are larger than those of some of the anterior segments-a difference which may have to do with the habit (so general among earthworms, at least of this country) of lying outside the burrow with the tail only concealed within. The first septum lies between segments v./vi. The septum between viii./ix. is missing, as is nearly universally the case with Perichceta. The septum between ix./x. is largely defective, though not absent; it consists chiefly of a strong muscular band on each side, which is attached to the insertion of the next following septum. Septa v./viii., x./xiii. are moderately thickened. In the hinder part of the body were paired masses of ccelomie cells, attached on either side of the dorsal blood-vessel, such as I have described in Perichceta. They were full of Gregarines. The pharynx is beset with numerous salivary glands, which extend back as far as the sixth segment. The gizzard is globular, not in any way elongated. The last heart is in segment xiii. The sperm-sacs are in segments xi., xii. ; there are, as usual, two pairs of sperm-duct funnels. 1 This is a little different from the segments originally selected (" On some Species of the Genus Perichceta," Y.Z.S. 1892, p. 157); but as the number culminates at xvi. I have thought it well to emphasize the fact by the formula. 2 In relation to this fact, it is interesting to observe that in Perichceta caducichceta (Benham, Ann. & Mag. Nat. Hist. ser. 6, xvi. p. 47, 1895) the set as upon this segment are absent. |