432 SANGUIFEROUS SYSTEM. 



moved by the lining vibratile cilia, are seen advancing and 

 retreating through the transparent tubular feet of these ani- 

 mals, conveyed from vessels and sacs extending along their 

 base. But the capillary veins of the asterias arise from the 

 gastric coeca, extend and anastomose along the course of the 

 mesentery, where they are freely aerated, and their united 

 trunks, disposed around the central cavity, give origin to the 

 arteries which traverse and nourish the rest of the body. 

 Into each division of the body, a large intestinal artery pas- 

 ses from the circular trunk around the stomach, and divides 

 into two branches, to be distributed on the two ramified 

 coeca of each. A single arterial trunk is distributed to the 

 feet of each of the rays, and the same number of trunks con- 

 tinue along the whole course of the rays to be distributed 

 on the segments and the superficial parts of the body. The 

 ramifications of these vessels are distinctly seen on the 

 stomach, the gastric coeca, and the ovaries, and in some 

 astei^us a cordeform enlargement is seen on the arterial 

 trunk, which is not developed in other species. In the 

 echinus, so closely allied to the asterias in all its organs of 

 relation, the same plan is perceived in the distribution of the 

 vascular system, a circular artery is observed around the 

 mouth, which sends out branches to the long alimentary 

 canal, and five branches proceed to form a vascular ring 

 around the opposite axis of the trunk. A large vein passing 

 forwards along the inner part of the mesentery, enters the 

 circular trunk around the mouth, and the arteries for the 

 tubular feet arise from this oral ring, as in the asterias. 

 The numerous veins ramified on the intestine and mesentery 

 of the holothuria (Fig. 114. /.), replenished with chyle from 

 that cavity, unite to form large arterial trunks, which distri- 

 bute their fluids over the complicated internal branchiee 

 (114. h. h.) 9 extended between the long turns of the intes- 

 tine (114. d. d.) The arterialised blood collected from the 

 branchial veins is sent forwards and backwards by systemic 

 trunks, the anterior of which forms the usual ring around the 

 oesophagus, while the posterior follows the course of the 

 intestine. The circular trunk around the oesophagus gives 

 off five arterial branches, which supply the apparatus of the 

 mouth, and the general parietes of the trunk, and extend- 

 ing their course backwards, parallel to the long muscular 



