NICOMACHE MACULATA. 305 



usual kinds of bristles, and a short distance beneath a single powerful spine, which appears 

 to be of special service to the annelid in its movements of extension beyond the tube. 

 The strong sharp points would instantly anchor the body either by impinging on the 

 tough lining of the tube or other hard surface externally. 



The fourth and fifth feet also occasionally have two of the strong spines, and the 

 former has a few hooks which differ from the typical forms behind in the greater 

 proportional size and elongation of the main fang and the upright position and blunt 

 condition of the spikes on the crown. The fifth foot has a large number of hooks. In 

 other examples the spines only extend to the fourth. The tuft of bristles on the throat is 

 also close to the base of the main fang, and the general outline of the neck, shoulder, and 

 short shaft differs. 



In the sixth segment the bristles and hooks are anterior; in the seventh they are also 

 anterior, and there is no furrow between this segment and the eighth. In the following 

 segments the bristles and hooks are posterior, and they continue so to the fourth segment 

 from the end of the series. The last three are short segments, and they bear their bristles 

 and hooks on the mid-lateral region. Most show a single ring between the last bristled 

 segment and the anal cup, but one shows two. 



The bristles of the last segments consist of rather strong capillary forms with distinct 

 wings and tapered tips which show no spikes, and a few more slender forms of the usual 

 character, with long, fine, hair-like tips and opposite spikes. 



The typical hook (Plate CX, fig. 13) differs from that of Nicomache lumbricalis and of 

 Arwidsson's var. borealis. The great fang makes a smaller angle with the neck, and five 

 teeth occur in lateral view on the crown above it. The backward curvature of the neck is 

 as great as in var. borealis, but the neck is longer, and the shoulder beneath it is perhaps 

 better defined. The tuft of bristles on the throat is separated from the fang by an 

 interval as great as in var. borealis. The hooks form a single row in each case, the rows 

 being short in the anterior segments, but at the seventh bristle-tuft each lies in the centre 

 of a long, elevated, glandular mass on the ventral surface, those following gradually 

 becoming ventrolateral in position, and separated from each other by a furrow in the 

 mid-ventral line. The hooks project from the surface and thus give most efficient 

 anchorage when in action. By the elevation of the pads the hooks in projection form a 

 curved ridge of golden points, and in life this can always be accomplished by muscular 

 agency. When loosened in their surroundings they entangle delicate forms like the 

 Ampharetidse, and it is difficult to remove these without rupture. 



Nicomache lumbricalis, which has sometimes been confounded with the present species, 

 is an arctic form which does not appear to extend to British seas. 1 In the large examples 

 of Nicomache lumbricalis procured in the ' Valorous ' Expedition of 1875 the neck of the 

 hook is shorter and more uniformly broad, the striae are confined to the beginning of the 

 distal region, the main fang makes a larger angle with the neck, and only three teeth 

 are usually visible on the crown in lateral view, and they are more erect. This form 

 makes a nearer approach to the hook of Arwidsson's var. borealis. The large Canadian 

 form, again, shows a much longer shaft, larger neck which widens distally at the striated 

 region, the main fang has a similar angle with the deck, and two teeth with traces of a 



I Vide Arwidssou, < Zool. Auzeiger/ Bd. xxxiii, 1908, p. 270. 



162 



