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Art. XXX.—On an Earthworm from the Auckland Islands—Notiodrilus aucklandicus.
[Read before the Otago Institute, 14th October, 1902.]
Plates XXII.-XXVI.
The material which forms the subject of the present note was collected by Captain Hutton during his recent trip to the southern islands. He was good enough to send it to me early in 1901. The collection consisted of six specimens, all belonging to the same species, which is new to science.
Notiodrilus aucklandicus, n. sp.
Colour.—The worms are, in the preserved condition, greyish in colour, with grey-brown clitellum, and the preclitellar region sienna-brown. The grey tone is due to the transparency of the body-wall allowing the contents of the gut to be seen; nevertheless, pigment dots are present in the body-wall.
Dimensions.—The largest specimen measures 93 mm., the smallest 78 mm.; two others are 82 mm. in length The diameter of the first is 2.5 mm. in middle of body, but of the smallest 3.5 mm. The worms are, unfortunately, very soft, and imperfectly preserved, so that in handling the dimensions vary. One of the medium-sized specimens consists of 107 segments.
The prostomium is imbedded about one-third into the peristomium, and is epilobic.
The eight chœtœ are separate: aa = dd, ab = ½ aa, bc = cd >ab.
The clitellum is not quite fully developed in any specimen, but in the most mature it extends from half 13 to half 17 (in two specimens covers only 13 to 16). The anterior region is complete ventrally, but the under-surface of the 16th segment is devoid of glandular tissue.
Genital Pores, &c.—The porophores on 17 and 19 are in line with chæta b, which, with a, is absent on these segments. Both these chætæ are present on the 18th segment. A spermatic groove, convex outwards, passes over this segment in the usual way. Accessory copulatory tubercles exist, though there is some variability in their distribution; but from an examination of the five individuals which exhibit them their location is as follows:—
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A. In line with chæta a: A pair of small tubercles on 17 and 19, near the anterior margin, and mediad of the porophores; a pair of similar tubercles on the 18th, near the hinder margin.
B. In line with chæta b: A pair of larger tubercles on segment 20, around chæta b (and, in one case, also on the 21st segment); a pair of similar tubercles on the 16th segment; and a pair on the 10th segment.
The spermathecal pores in the usual position, in line with chæta b. The nephridiopores in line with chæta c.
Dorsal pores are present, at any rate, behind the clitellum.
Internal Anatomy.
The dorsal vessel is single; the last heart is in the 12th segment.
Alimentary System.—There is no gizzard perceptible on dissection. The œsophagus bears two pairs of distinct glands, in segments 13 and 14 respectively. The intestine commences in the 16th segment, and is without a typhlosole.
Reproductive System. — The testes, sperm-ducts, ovaries, and oviducts occupy the usual positions. There are two pairs of botryoidal sperm-sacs, in the 11th and 12th segments. The spermiducal glands are long, folded, and tubular, but apparently of rather looser texture than is usual in Acanthodrilids. Each is provided with a narrow and long muscular duct, which is distinctly swollen where it penetrates the body-wall. Each gland passes through four to six segments, and even the duct passes backwards into the segment following the pore.
Penial chætæ are present. Each sac contains a couple, a longer and shorter, of functional chætæ, together with their replacers. Both have the same general form. The tip is somewhat spoon-shaped, while the shaft is ornamented by numerous fine transverse and serrated ridges.
The spermathecæ are in the usual segments. Each is a globular sac, with distinct narrow duct about half as long as the sac itself. This duct receives, as it passes through the body-wall, two sausage-shaped diverticula, which thus seem to be independent of the sac.
Remarks.
This worm differs from N. macquariensis, F.E.B., in several respects, as a comparison with the account* published
[Footnote] * “On some Earthworms from the Islands around New Zealand,” (Trans. N.Z. Inst., xxxiii, p. 132). In that article I stated that the penial chætæ are “hooked” at the tip. This I now find, from observation of several specimens, to have been an accidental bending of the soft tip. The hook exists in the preparation I then made, but I have not observed it in other cases.
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by me in 1900 will show. There is, however, a special interest attaching to both these species, since they agree more closely with the species of Notiodrilus found at the Cape of Good Hope and at South Georgia, Falkland Islands, and Tierra del Fuego, than they do with the species of the genus occurring in New Zealand itself.