SANGUIFEROUS SYSTEM. 443 



arteries to the lateral pairs of feet. In the cephalo-branchiate 

 marine serpulce and sabellce, the arterialised blood is returned 

 by the branchial veins to two elongated sinuses placed at the 

 sides of the oesophagus, the aorta and vena cava occupy 

 the median plain, giving off symmetrical lateral branches, 

 and the dorsal vessel appears slightly enlarged in each 

 segment. The branchial veins of the amphitrite likewise 

 convey the arterialised blood to two vesicular sinuses which 

 unite below the oesophagus, and from these branchial sinuses 

 in the terebelloe the two lateral systemic veins take their 

 principal origin. 



From the deep red colour of the blood, and the colour- 

 less transparency of the general tissues of the body, in the 

 common peetinaria of our sandy coasts, the pulsations of 

 the wide dorsal artery are easily observed, extending in 

 successive waves from behind forwards, and also the nu- 

 merous branches sent off laterally, which reduce the calibre 

 of this great artery at its anterior part. Besides the usual 

 median dorsal artery, and the median ventral trunk above 

 the nervous columns, in the pleione carunculata, there are 

 two lateral dorsal vessels which communicate freely, by anas- 

 tomosing branches, with the median dorsal artery, and also 

 two lateral longitudinal ventral veins, which send numerous 

 branches to the branchiae. The arterialised blood appears 

 to be collected from the branchise by the lateral dorsal ves- 

 sels, and to be transmitted partly by their internal anasto- 

 mosing branches, into the median dorsal artery, and partly 

 by their own branches to the principal organs of the body. 

 The venous blood of the system is collected from the super- 

 ficial parts and the internal viscera into the great lateral 

 veins, and is thence transmitted through the minute laminae 

 of the external branchiae, before it is received by lateral arte- 

 rial trunks for the nourishment of the system. The highly 

 sensitive and muscular pharynx is provided with a large and 

 distinct plexus of vessels, connected, like the numerous 

 plexuses of the alimentary canal, with the great inferior 

 lateral veins, which give origin to the branchial arteries. The 

 median dorsal artery is here chiefly connected with the ali- 

 mentary canal, as the median ventral vein is, in this and 

 most other articulated animals, connected with the nervous 

 columns. From the equal development of the great vascular 

 centres throughout the body of the annelides, and the nume- 



