472 



GLTCBRID^J 



distinctly diminishing toward the tail, which terminates in two short cirri. The segments 

 are narrow, and have two or more rings. Feet with two divisions — a dorsal and a ventral, 

 or with the latter only. Bristles of two kinds, viz., simple dorsal bristles with a narrow 

 wing and serrated edge, and compound bristles, with the tips of the shafts dilated and 

 split for the tapering serrated terminal piece. 



Proboscis 1 powerfully muscular, with the first region easily protrusible, massive, 

 glandular, with four hooked teeth which have a bifid or simple basal spur, and the pairs 

 of which can cross each other vertically. Glands occur at the base. Alimentary canal 

 simple. 



Blood-vessels present or absent. The coelomic corpuscles are large and tinted 

 reddish, and move with special activity at the ciliated bases of the feet. These corpuscles 

 contain haemoglobin. 3 



The body-wall in the Grlyceridse (Fig. 90) is distinguished by its firmness and 



Fig. 90. — Transverse section about the anterior third of Glycera lapidum. Enlarged. 



muscularity. The cuticle is fairly thick, and is tough. Beneath is a hypoderm of 

 moderate depth, with numerous nuclei, which stain deeply, and areolae — lined 

 internally by a thin basement-tissue. The circular muscular coat is of exceptional 

 thickness. It diminishes (in transverse section) almost to a few fibres in the mid-dorsal 

 line (where the hypoderm is thicker), whilst ventrally, on each side of the nerve-area, it is 

 also thin, the space being considerably broader than that in the mid-dorsal line. A 

 narrow belt of circular fibres crosses this area ventrally to the other side, but 

 very few turn upward to clasp the inner ends of the ventral longitudinal muscles. 

 The dorsal longitudinal muscles are massive, separated by a gap in the middle line, 

 and with a well-marked lobe curved inward ventrally to a blunt point. They cover 

 a proportionally greater area than the ventral muscles, which form a long and slightly 

 fusiform mass on each side, and meet over the nerve-cords in the middle line as 

 they lie in a triangular area of their neuroglia — broad externally and pointed internally. 

 Each cord has a neural canal of moderate size at its upper third near the middle line. 

 It is doubtful, however, if in any respect such appears " to have generally the 



1 Vide Jourdan, ' C. R. Ac. Sc./ t. cxii, p. 882. 



2 Bay Lankester, f Proc. Roy. Soc./ No. 140, 1873, p. 3 (sep. copy). 



