80 CLASS VIII. VERMES OR WORMS. 



thus, as it were, being moored or anchored, and secured from 

 the influence of the waves. The two valves of their shell are 

 held together by strong muscles which pass from one to the 

 other ; and when these are relaxed, the shells open mechani- 

 cally, by means of an elastic substance placed in the hinge 

 of the joint which connects them. 



There are several other orders of the Mollusca, but the 

 characteristics by which they are distinguished are too obscure 

 3r minute to be here described. 



SECTION IX. 

 Class VIII. Vermes or Worms. 



THE term Vermes or Worms has been used with great 

 vagueness in natural history, and employed to designate ani- 

 mals to which the name was not appropriate. It is now, 

 however, more restricted in its application, and is made to 

 include only a small class of animals, which have some cir- 

 cumstances in common with each of the three classes last 

 described, but still not exactly resembling any. They are 

 sometimes called, by way of distinction, Worms with red blood, 

 as they are the only invertebral animals which have red blood ; 

 and sometimes Annelides, from the structure of their body, 

 which is of a cylindrical, elongated shape, divided into a great 

 number of rings. 



Their nervous system resembles that of the Insects and 

 Crustacea. Their organs of sense consist merely in some 

 fleshy tentacula, which surround the mouth, and answer the 

 purpose of feeling and touching. In some species, certain 

 black points appear around the head, which have been sup- 

 posed to be eyes, but this is doubtful. Their blood is nearly 

 of the color of that of the vertebral animals, but not of so 

 bright a red. It circulates in a double system of vessels, but 

 there is no distinct, fleshy heart to give it motion. They 

 breathe by means of branchise, which are sometimes within 

 and sometimes without their bodies. They have no limbs, 

 but on each of the rings, of which their bodies are composed, 

 are little bristly projections, which answer in some sort the 

 purpose of feet. Their mouths are sometimes armed with 

 jaws, and sometimes consist in a mere tube or sucker. 



Their bodies are soft and compressible. All, except th 



