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 worms. 

 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 j 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 

 Echinidce, 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 Echinida 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 

 ijichesj the snail, which has no foot or similar processes, 

 B 4 



