SCALISETOSUS COMMUNIS. 375 



tioned by Ehlers. Every .little papilla has its nerve-twig, and the granular enlargements 

 are connected with the system like fruit on the tips of a much ramified wall-tree. 



In life the scales are quite translucent, sometimes presenting towards their anterior 

 and posterior borders numerous yellow patches at the papillae, or, as in the figure, 

 simply dotted with white specks. In others they have a faint purplish-brown tinge, 1 

 enlivened by orange and yellowish specks. The brownish tinge in some is towards the 

 inner border. 



This active and irritable annelid frequently throws off its scales, but, as in other 

 cases, they are readily reproduced, an interesting account of their development having 

 been given by Ehlers. 



De St. -Joseph found a number of specimens of Pedicellina belgica, van Beneden, 

 on the under surface of the scales. 



Feet. — The first foot has a spine, but no bristles in the available specimens. De 

 St. -Joseph thinks this is the normal condition, but it is uncertain. 



The dorsal division of the foot (Plate XXX, fig. 9) forms a short and broad process 

 bearing a series of translucent slightly curved bristles (Plate XL, fig. 17), which are not 

 much tapered distally. The rows of spines (or frills), about eight in number, are wide 

 apart inferiorly, while the tip of the bristle is notched as if from a minute claw or 

 secondary process. So homogeneous are these bristles that the usual longitudinal striae 

 have disappeared, and they resemble crystalline structures. In the ventral division 

 the spine forms the apex of a somewhat conical lobe, the upper slope, however, being 

 the shorter. The bristles (Plate XL, fig. 18) are equally transparent, but are slender 

 and elongate, the shaft terminating superiorly in a dilatation with a spinous frill, which, 

 like those of the dorsal, seems to be continuous. Erom this part the spinous region 

 passes with a slight bend towards the dorsum, and ends in a w r ell-marked hook with a 

 small secondary process — apart from its base beneath. The tip is flattened and not 

 much tapered, while the oblique rows of spines are somewhat adpressed. Little 

 change takes place in their structure in the posterior feet. The bristles seem to have 

 few parasites. 



The dorsal cirri (Plate XL, fig. 19) are comparatively long, with a slightly dilated 

 portion beneath the long filiform tip. A yellowish belt, or in some a white ring, 

 marks the dilated portion. A few minute clavate cilia occur on their surface, and to 

 these nerve-twigs proceed. The nerve in the centre of the cilium appears to form an 

 enlargement in the opaque region at the base of the filamentous tip, and then continues 

 onward to the extremity. The posterior cirri are longer and more slender, and the 

 dilatation below the filiform tip is distinct. 



The ventral cirri are rather long, smooth and tapering, their tips extending beyond 

 the bases of the bristles. 



Reproduction. — Specimens procured in Bressay Sound in July showed ripe eggs, 

 and they were extruded in masses on rupture of the body. A male captured off Peel, 

 in the Irish Sea, bore ripe spermatozoa the same month. 



Development. — A young form measuring a little over 1 mm. occurred amongst the 



1 De St. -Joseph calls it roseate. 



49 



