CHAP. I. RANK OF THE TESTACEA. 7 



have removed all difficulty^ and even doubt. The Anne- 

 lides have the joints of their bodies, like the common 

 earth-worm, disposed in rings, but yet they offer the 

 extraordinary character of red instead of white blood : 

 hence^ they are always called red-blooded w^orms. 

 There is, to be sure, no vestige of any internal support 

 to the body, such as we have seen in the Cephalopoda ; 

 but every one must be struck with the resemblance 

 which exists between a worm and an eel, — the one being, 

 in form, almost the miniature of the other. This re- 

 semblance, moreover, is carried much further by certain 

 eel-shaped fishes, which are destitute, not only of fins, 

 but of eyes ; while in others^ as the genus Myxine, the 

 vertebral column, or back-bone, is hardly to be dis- 

 tinguished. It is impossible, therefore, for this grad- 

 ation to be more perfect. Every naturalist of the 

 least repute has viewed the connection of the Anne- 

 lides to' the fishes in this light ; and thus are all the 

 classes of the animal kingdom united into one vast 

 circle. 



(8.) Of the three divisions of the Mollusca, — namely, 

 the Testacea, the Radiata, and the Acrita, — it is obvious 

 that the latter are the lowest in the scale of animal life; 

 the superiority of the Testacea to the Radiata must 

 also be admitted, when we come to compare the or- 

 ganisation of one with the other. The shells of the 

 Echinid(B, the most typical group of the radiated animals, 

 are certainly as beautiful and complicated in their con- 

 struction — although not, perhaps, in outward appear- 

 ance — as those of the Testacea ; but we must look to 

 the animals themselves. The EchinidcE show not the 

 least indication of that form which belongs to verte- 

 brated animals : although provided with short tentacula, 

 which are supposed to assist them in removing from 

 place to place, they yet move so slowly, that a snail, in 

 comparison, may be said to run : thus the Echinus, al- 

 though with tentacula, — which are supposed to perform 

 the office of feet, — can scarcely remove itself a few 

 inches; the snail, which has no foot or similar processes, 



B 4 



