338 



POLYCHAETA 



CHAP. 



brown, marked with white bands in a fairly regular fashion. 

 Each gill filament has, just below its tip, a compound eye, con- 

 sisting of several lenses and retinae. North Sea and Medi- 

 terranean. 



Dasychone bombyx Dalyl. is a short, comparatively stout worm 

 usually 1 to l| inches long ; reddish -brown in colour, with a 

 darker spot on each side of every segment. The gills are lighter 

 with greenish marks. This worm may readily be recognised, for 

 each of the gill filaments carries some six to ten pairs of dark 

 compound eyes at intervals along its length, and near to each pair 

 there arise two short processes from the outer side of the fila- 

 ment, which are known as " dorsal appendices." The worm 

 forms a tube of mud, more or less mixed with sand. It occurs 

 at low water and to some depth round the coasts of the 

 Atlantic, North Sea, and Mediterranean. 



Chone infundibuliforwds Kroyer may be recognised by the 

 absence of lobes on the collar, the presence of a membrane con- 

 necting the gill filaments, and the passage of the faecal groove 

 along the dorsal surface of the thorax. The worm is 6 inches 

 long, with purple gills, spotted with yellowish-white. The tube 

 is formed of yellowish membrane covered with sand, and is 

 fixed to stones and other objects. Potamilla reniformAs Mull, 

 is about 3 inches long, with about twelve brown gill fila- 

 ments, some of which have eyes near the base. The tube 

 is transparent and horny, with sometimes a slight covering of 

 sand. Found in old oyster shells. North Sea, Atlantic, Medi- 

 terranean. 



The genus Spirographis contains one of the largest European 

 Sabellids, S. spallanzanii Yiv., which occurs off the Channel 

 Islands and in the Mediterranean. The two gill plumes are 

 unequal ; the large rone forms an upright, spirally -coiled 

 column. 



Eam. 2. Eriograpliidae. Myxicola infundibulum Mont, has its 

 gill filaments connected by a membrane reaching nearly to their 

 tips. Each gill plume forms a semicircle ; there are no eyes ; the 

 peristomium does not form a collar ; no gland shields. The worm 

 requires neither of these structures, since it is practically a free- 

 swimmer, envelopes itself in mucus, and moves tail first. The 

 faecal groove is not well marked, though continued dorsally. In 

 the abdomen the tori uncinigeri extend dorsally and ventrally 



