Benham. — On Acanthodrilus uliginosus. 125 



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arranged in four couples, one couple on each side being 

 latero - ventral, the other latero-dorsal. These couples are 

 nearly equidistant, and form four lines along the entire 

 length of the body. The body of the worm is quadrangular 

 in section, except in the anterior twenty or so segments, and 

 these couples of chaetae are situated at the angles. Each 

 segment, too, is provided with a pair of small but distinct 

 pores at its anterior margin. These are the nephridiopores, 

 the apertures of the excretionary organs. The first pore lies 

 at the anterior boundary of the 3rd segment. A very re- 

 markable arrangement is presented by these pores in many of 

 our New Zealand worms, in that they are situated alternately 

 in front of the upper and in front of the lower couple of 

 chaetae. This alternation is not absolutely regular, and, in 

 fact, up to the 10th or 11th segment they are in line with the 

 upper couple of chaetae. 



Further, in the median dorsal line, on each of the inter- 

 segmental furrows, behind the clitellum, is a small dorsal 

 pore, which is, however, not easily seen in preserved speci- 

 mens. 



The clitellum, or saddle - shaped girdle, covers segments 

 11-19, and may even encroach occasionally upon the 13th 

 or 20th segments. The glandular thickening of the skin 

 covers the back and passes down the sides as far as the 

 level of the ventral chaetae, leaving the ventral surface free. 

 Within this area, in the hinder part of this region, are four 

 noticeable circular papillae, usually pale in colour ; they lie 

 on the 17th and 19th segments in pairs, in line with the ven- 

 tral chaetae. Each papilla is provided with a pore — hence they 

 are termed " porophores" — which allows the protrusion of a 

 couple of long, fine bristles, known technically as " copulatory 

 or penial chaetae " — the modified ventral chaetae of these seg- 

 ments. These are about three times the length of ordinary 

 chaetae, and of a different shape (see figs. 9 and 10). The two 

 porophores of each side are connected by a distinct longi- 

 tudinal furrow, with well-marked lips, passing from the pore 

 on the 17th, across the 18th segment, to the pore on the 

 19th segment. This " spermatic groove " is straight, and 

 passes between the ventral couple of chaetae of the 18th 

 segment. At this point is situated the " male pore," the 

 external aperture of the sperm-duct ; a minute pore, only 

 visible with difficulty. On the 14th segment are the paired 

 " female pores," the apertures of the two oviducts, lying just 

 in front of the ventral chaetae. Further forwards, and placed 

 on the intersegmental groove separating segments 7/8 and 

 8/9, on each side, are the two pairs of spermathecal pores , 

 also in the line of the ventral chaetae. 



