Natural History of the United States. 245 



2. Classes, we are told, refer to the " ways and means em- 

 ployed" in the structure of animals, or to the "combinations of 

 their different systems of organs", — somewhat vague grounds, 

 which we may perhaps illustrate by an example, all the more clear 

 because very familiar. Let us suppose the animal kingdom, not 

 the living clay from the hand of the Great Potter, but a collection 

 of earthenware vessels appertaining to table uses; and that we 

 have to effect an orderly arrangement of the mass. Fiist we 

 might observe that among this collection of vessels of all shapes 

 and sizes, there were only a few different patterns, — some all 

 white, some white and gold, some with a landscape, some with 

 a flower; and each having in connection with this its peculiar 

 style of form. We might then adopt, as our first basis of arrange- 

 ment, pattern or type, both for simplicity and as indicating in the 

 highest respect the mind of the artist. Having formed four great 

 heaps on this ground, we should find that we had in each, vessels 

 differing in material, in shape, in use, in complexity of parts; and 

 we might carry out our farther division on any of these grounds. 

 According to our author, we take the material, whether common 

 earthenware or china, for instance, as our ground, this correspond- 

 ing to ways and means of construction. Just, however, as we 

 found that type could not be dissociated from rank, so neither 

 can ways and means; and these moreover have a direct relation 

 to use, and until we had read the views of Prof. Agassiz, we had 

 supposed that this, or perhaps more generally, position in the eco- 

 nomy of nature, was the predominant idea in the class. Let us 

 place before our minds the classes of Invertebrates as proposed by 

 Agassiz : — 



Radiata. Mollusca. Articulata. 



1. Polypi. 1. Acephala. 1. Worms. 



2. Acalephae. 2. Gasteropoda. 2. Crustacea. 



3. Echiiiodermata. 3. Cephalopoda. 3. Insects. 



Now, it is quite evident that in these several classes the ground 

 insisted on by our author, the manner of combination of the struc- 

 tures, is highly distinctive, and affords a good ground for discri- 

 mination in practical Zoology ; but it appears to us that there is 

 a higher reason in the distinction of these groups, which refers to 

 the idea of modification of the type with reference to uses or place 

 in niture. First, then, we would observe that there is a manifest 

 gradation in elevation of rank. The Echinoderm, Cephalopod, and 

 Insect, are respectively at the head of their branches, representing. 



