28 Prof. M'lntosh's Notes from the 



ventral blood-vessel which has remarkably thick walls, so 

 that at first sight the mass resembles the halves of a narrow 

 elliptical ganglion or flattened cord, after the character of 

 that in Arenicola, since the actual cords are difficult to 

 recognize. The thickness of the walls of the vascular trunk 

 would indicate special contractility in this region. The 

 hypoderm is thus divided into lateral lobes with a slight 

 median ventral ridge; the whole being glandular. 



The body-wall in Dasychone dalyelli {argus) has externally 

 the cuticle and a thick hypoderm, and there is a glandular 

 ventral belt of great depth as in Sabella, with a median 

 notch. The circular muscular coat appears to be compara- 

 tively thin, though continuous. The dorsal longitudinal 

 muscles are in section rather broad and thin, the thickest 

 end being external, and a hiatus occurs in the mid-dorsal 

 line. A considerable gap exists between the ventral longi- 

 tudinal muscles, which are about the thickness of the dorsal, 

 though narrower, and Avithout curvature, apparently from the 

 feebleness of the oblique muscles. At intervals somewhat 

 powerful muscular bands slope downward and inward, to be 

 attached to the complex area above the nerve-cords, but the 

 system is less marked than in Sabella. The alimentary 

 canal has its median dorsal and median ventral mesenteries. 

 The nerve-trunks lie more distinctly under the inner edge 

 of each ventral longitudinal muscle, and no neural canal is 

 present. The fibres of the circular and oblique appear to 

 cross between them, and from the trunks fibres radiate into 

 the glandular coat outside. The ventral longitudinal mus- 

 cular layer is often broken up into several fasciculi. 



The structure of the body-wall in Chone infundibuliformis, 

 Kroyer, introduces a new type into the series, were it only 

 for the remarkably coiled arrangement of the muscular 

 fasciculi of the longitudinal muscles in transverse section. 

 The cuticle covers a hypoderm well developed and highly 

 glandular throughout, the long cylindrical cells being 

 characteristic, especially when slight softening of this coat 

 occurs. In the mid-dorsal line is a deep groove, and its 

 bottom and sides show a somewhat finer granular structure, 

 so that it may be a more sensitive area than the general 

 surface. A decided thickening of the hypoderm takes place 

 in the mid-ventral line, and it tapers to the normal thickness 

 in the ventro-lateral region. The circular muscular coat is 

 well developed and continuous, modifications occurring at 

 each foot. The dorsal longitudinal muscles are largely 

 developed, and, like the ventral in section, are in two concen- 

 trically arranged bands, the outer layer, however, extending 



