OCR Text |
Show 1885.] NEW-ZEALAND EARTHWORMS. 829 vasa deferentia, and are consequently not obvious on a dissection of the worm, since they are largely concealed by the funnels and are only evident on raising the latter. In transverse sections (Plate LII. fig. 9) they are very conspicuous, and although attached by a pedicle to the sides of the funnel, their tissue is unmistakably different from the elongated ciliated celis which compose the latter, and is absolutely similar to that of the homologous glands in the other species ; the change in the position of the glands naturally moves them a segment further forward than in A. dissimilis, and there is consequently a segment lying between the ovaries and the posterior pair of glands. Copulatory Pouches.-Copulatory pouches (spermathecse) are present in all three species, and have a characteristic form which serves to discriminate the species. In all there are two pairs which are situated in the "th and 8th segments, and open on to the exterior in the furrow which separates each of the segments from the preceding one, in front of the ventral pair of setse; in A. multiporus the apertures of the copulatory pouches are related to the outermost of the two ventral setse. The copulatory pouches are large oval sacs, communicating with the exterior b}7 a short, thick-walled duct. In A. multiporus the pouches appeared to be without diverticula; in A. dissimilis each of the copulatory pouches (Plate L I U . fig. 9) is furnished with a pair of long diverticula opening into the duct of the pouch, one on either side. The disposition of the diverticula varied in different specimens : in one specimen the diverticula were contained in the same segment as the pouch, with the exception of one of the two diverticula of the posterior left-hand pouch, which passed through the mesentery and projected into the 8th segment; in another example both diverticula of the two anterior and one of the posterior pouches, in the segments anterior to those in which the pouches themselves were situated. In A. nova zelandia the terminal portion of the duct of the copulatory pouch is beset with a great number of small diverticula arranged in the form of a rosette (Plate L U I . figs. 3 and 8) ; as in A. dissimilis, the diverticula sometimes seem to lie in the same segment as the copulatory pouch itself, sometimes in the segment in front. In Acanthodrilus dissimilis the structure of the copulatory pouches and of their diverticula undergo certain changes during the life of the animal, which are evidently connected with the process of fecundation. In individuals, which I take to be not completely mature, the copulatory pouch has the structure illustrated in Plate LII. fig. 8 ; within the muscular layers, which are thin and abundantly vascular, is a layer of tall, columnar, nucleated cells ; on a superficial view these cells present the appearance indicated in fig. 7 of the same Plate; they are extremely narrow and somewhat hexagonal in contour; the epithelial lining of the copulatory pouch is thrown into folds which are often very regular in their arrangement (Plate L I U . fig. 7), but only consist of a single layer of cells. In another individual the structure of the epithelium of the copulatory pouch is somewhat more complicated : a small portion PROC. ZOOL. Soc-1885, No. LIV. 54 |