330 



POLYCHAETA 



Polycirrus aurantiacus Gr. is sometimes placed in a special 

 sub-family, as it has no gills. The numerous tentacles are 

 very long, and arise from a great hood over the mouth ; the 

 capillary chaetae commence in the first segment and extend for 

 about half the length of the body ; the uncini commence in the 

 ninth segment. The ventral " shields " are paired. The animal 

 is highly coloured ; its phosphorescence and its distastefulness 

 have already been mentioned on p. 294. In Terebellides stroemi 

 Sars, four comb - like gills arise from a single common thick 

 peduncle on the back of the second segment (Fig. 176, F). The 

 ventral surface of the body bends upwards anteriorly so as to 

 bring the mouth to the dorsal surface. 13 to 

 16 fathoms, muddy bottoms, North Sea and 

 Mediterranean. 



Fam. 3. Ampharetidae. This family differs 

 from the Terebellids chiefly in the shape of the 

 head and in the presence of a bundle of strong 

 chaetae (or paleae) on each side of the head in 

 front of the gills, of which there are four on 

 each side. Each gill is a simple filiform pro- 

 cess, considerably longer than the tentacles, 

 which are very few in number. Ampliicteis 

 gunneri Sars, Ampharete gracilis Mgrn., and 

 Melinna cristata Sars, occur on our coasts. 



Fam. 4. Amphictenidae. This contains the 

 interesting genus Pectinaria, in which the head 

 is protected by great golden chaetae on the 

 second segment ; they are flattened, curved, and 

 pointed, and are arranged in a single trans- 

 verse row on each side, serving as an oper- 

 culum to the tube. The posterior end of the 

 worm has undergone great degeneration, and is 

 podium ;ch, paleae; represented by a small leaf-like " scapha " which 

 ^,'prostomiaitenta- serves to close the tube posteriorly. The worm 



cles; I, peristo- j g ji j ncnes in length and consists of only 

 mium. (From z * 



Maimgren.) twenty segments, of which seventeen are chae- 



tigerous. The tube is nearly cylindrical, but 



wider anteriorly than posteriorly (Fig. 152, p. 288); the sand 



grains are uniform in size, and are embedded in the secreted 



mucus in a very regular way, the surface being smooth both 



Fig. 177. Pectinaria 

 belgica Pall. 



Slightly enlarged. 

 a, Netiropodial 

 chaetae ; b, noto- 



