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Internal Anatomy (Plate 10, fig. 2)
The septa vii/viii, viii/ix, ix/x, x/xi, xi/xii, xii/xiii and xiii/xiv are thickened and muscular.
Alimentary Canal. The pharynx is small and muscular and occupies the first four segments. There is no proventriculus. The gizzard is slender, but has thick muscular walls, and is situated in v. The oesophagus extends from vi to xiv and there are no oesophageal glands. The intestine commences in xv.
Vascular System. The dorsal blood vessel is unpaired throughout its length. A slender, unpaired, supra-intestinal vessel passes through x–xii and from it arise three pairs of dilated hearts, a pair in each of x, xi and xii.
Reproductive System. There are two pairs of small compact testes, a pair in x and a pair in xi, one on each side close to the ventral nerve cord in each segment. A pair of ovaries occurs in a similar position in xiii. Each ovary consists of a cluster of thread-like structures arising from the anterior septum of xiii. There are two pairs of spermathecae, a pair in viii and a pair in ix.
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In the specimen examined both the spermathecae of ix appear to lie on the right hand side of the ocsophagus, although the ducts open one on each side of the segment, as is normal. The left spermatheca has probably been twisted under the oesophagus by the contortion of the earthworm's body when it was killed. Each spermatheca consists of an ovoidal sac, opening by a long, muscular duct to the exterior, and a pyriform diverticulum opening into the medial aspect of the spermathecal duct, close to distal end of the duct. (Plate 10, fig. 3.) The prostates are simple tubular organs with unbranched axial canals. They are of unequal extent, the left prostate commencing from the duct, which passes through xviii and xix, and extending back through xx and xxi into xxii, where it terminates in a dorsally directed portion, and the right arising from its duct in xviii and extending around the lateral surface of the intestine in xix to terminate on the left dorso-lateral surface of the intestine in xix. (See Plate 10, fig. 2.) There are four pairs of vesiculae seminales, a pair in each of ix x, xi and xii Those of ix and xii are much smaller than those of x and xi.
A broad band of small micronephridial tubules extends across the ventrolateral and lateral aspects of the body-wall in each segment.
Remarks. Although the two species are superficially distinct, M. viridis very closely resembles M. maorica in its internal anatomy. It can be distinguished from M. maorica by its possession of four pairs of vesiculae seminales (M. maorica has only three pairs).
Megascolides ruber n.sp. (Plate 11, figs. 1–3)
A single specimen of this dark red earthworm was collected from Awapuka clay near the summit of the Mangamuku Range, North Auckland, in a large area of native rain-forest. The posterior portion of the specimen is missing, so the length cannot be determined. The average diameter is 4·5 mm.
The prostomium is epilobous. The clitellum covers xiv to xviii and is lighter in colour than the rest of the body. The chaetae are lumbricine in arrangement, eight per segment. On segment xxii their arrangement is as follows:
ab = 1.25 mm.; cd = 2 mm.; bc = 1.5 mm.; aa = 1·5 mm.; dd = 3 mm.
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There are two pairs of spermathecal pores, a pair at 7/8 and a pair at 8/9, in line with chaeta b. There is a single, unpaired, median, ventral female pore on xiv slightly anterior to the line of the chaetae on that segment. A single pair of prostatic pores occurs on xviii. Each of the prostatic pores is situated in the centre of a cuplike depression, with a raised tumid edge, in line with the chaetal interval ab on each side. Chaetae a and b are absent on xviii.