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Internal Anatomy (Plate 116, fig. 2)
There are no specially thickened septa.
Alimentary Canal. The pharynx occupies the first four segments. There is a large, thick-walled gizzard in vi, connected to the pharynx by a short, thin-walled proventriculus. The oesophagus is narrow and extends from vii to xvii and has a prominent pair of calciferous glands in xv. The intestine commences in xviii, is thin walled and has a typhlosole.
Vascular System. The dorsal blood vessel is paired, but the two vesels fuse at septum vii/viii and remain fused anterior to that point. There are four pairs of dilated hearts in segments x, xi, xii and xiii.
Reproductive System. There are two pairs of testes in × and xi, and a single pair of ovaries in xiii. There are two pairs of spermathecae in viii and ix. Each is a large, round, laterally compressed sac opening to the exterior by a short, narrow duct. Two small diverticula, one anterior and one posterior, open into the proximal region of the duct. (Plate 116, Fig. 3.) Two pairs of convoluted prostates occur in xvii and xix, each prostate wholly confined to one segment. I can find no penial chaetae, and there is no sign of the copulatory muscles frequently found in the region of the prostates in the genus Octochaetus. There are two pairs of racemose vesiculae seminales in xi and xii.
Micronephridia commence in v. In that segment they form a cushion-like mass of long tubules on each side of the segment, but in the segments posterior to v the usual arrangement of a band of tubules on the lateral aspects of the peritoneum in each segment is found.
This species, in its external features and internal anatomy, shows very close resemblance to O. michaelseni (Benham, 1904). The dorsal blood vessel becomes paired at vii/viii, there is a prominent pair of calciferous glands in xv, there are two pairs of spermathecae, all characters shared with O. michaelseni, but the intestine of O. sylvestris commences in xviii while that of O. michaelseni commences in xvi, the spermathecae of O. xylvestris are rounded and have two very small diverticula opening into the medial aspect of the spermathecal duct while those of O. michaelseni are of an irregular bilobed form and
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appear to have no diverticula, and in other smaller points of external and internal anatomy the two species differ.
Octochaetus brucei n.sp. (Plate 117, figs. 1–3)
A single specimen of this species was obtained from Kiwitea loam under ngaio and tawa in the R. C. Bruce Park, a few miles south of Hunterville. It was light pink in colour and the clitellum was not obvious.
The species is 175 mm. in length and 9 mm. in diameter and has 431 segments. The segments are biannulate. The prostomium is prolobous. There are eight chaetae on each segment, arranged in four pairs, a pair in a ventral position and a pair in a ventro-lateral position on each side of each segment. On xxiv, the arrangement is as follows:
ab = cd = 0·25 mm.; bc = 3 mm.; aa = 4 mm.; dd = 17 mm.
There are two pairs of spermathecal pores, a pair at 7/8 and a pair at 8/9, in line with the chaetae ab. The female pores are on xiv, one on each side, anterior and slightly medial to chaeta a. There are two pairs of prostatic pores, a pair on xvii and a pair on xix, each pore opening at the apex of a low mound-like tumid area in line with the chaetae ab. A narrow groove joins the two prostatic pores of each side. This groove runs along the centre of a low tumid ridge joining the two prostatic papillae of each side and passes between the chaetae a and b on xviii. A male pore is situated in the groove on each side, between chaetae a and b on xviii. There are no tubercula pubertatis.
Dorsal pores commence at 19/20 and occur in every intersegmental groove posterior to 19/20. There are no nephridiopores.