BY WILLIAM A. HASWELL. 343 



His description begins with the branchial vessels. In each 

 bianchia there are two vessels, communicating with one another 

 at the extremity of the filament. To the bases of the branchiae 

 the blood is carried by a canal coming from the neighbourhood of 

 the end of the dorsal contractile trunk. This canal divides into 

 branches for the branchial filaments (one to each), and also gives 

 off a pair of branches to the tentacles. 



The dorsal contractile trunk or heart, he states, is united 

 directly with the ventral at a point below a pigmented spot 

 which he regards as a visual organ. Further back it gives off 

 various branches, the course of which is described. One of the 

 two largest pairs of these is directed forwards ; it is cemented to 

 the inner surface of the skin in its dorsal part. The second pair, 

 which is the larger, takes origin a little below the first and runs 

 backwards ; it is also cemented to the skin, and it terminates 

 abruptly at the sixth pair of parapodia. Behind this there is no 

 dorsal vessel proper. The heart terminates behind in the wall of 

 the stomach in a system of sinuses, and Jacquet conjectures that 

 the anterior dilated part may have a glandular wall secreting 

 some digestive substance, which is carried to the stomach in the 

 blood ; the plexus of sinuses extends backwards in the wall of the 

 intestine. A ventral vessel extends from one extremity of the 

 body to the other. In the neighbourhood of the mouth it divides 

 into two branches, which pass round the cesophagus to unite with 

 the anterior end of the heart. He contrasts the arrangement 

 described with that which is given by Quatrefages for Chloraema, 

 and draws the inference that there is a considerable amount of 

 difference in internal structure between the two genera. 



There would thus appear to be a considerable amount of diffe- 

 rence in the arrangement of the vessels in the various genera. 

 As far as my own observations on this subject extend, the 

 following would appear to be the general features of the vascular 

 system in this family. There is a peri-intestinal sinus or plexus 

 of sinuses in the wall of the alimentary canal. This terminates 

 in front at the cardiac end of the stomach, and from it runs 

 forwards a large median dorsal vessel or heart, which is subject 



