202 ZOOLOGY. 



And this, in fact, is what naturalists have done. They 

 have divided the animal kingdom into a certain number of 

 groups of the first degree, each characterized by certain pecu- 

 liarities of structure. They next divide each of these groups, 

 and characterize the secondary groups thus formed in the 

 same manner. These secondary groups are in their turn 

 divided, and the sections multiplied as required, until at last 

 nothing is left in the same group but the different individuals 

 of the same species. 



Classification, then, is a sort of catalogue raisonne, in 

 which all beings are arranged according to a certain order, 

 and reunited into groups, recognisable by determinate cha- 

 racters, which in their turn are reunited into other groups of 

 a still more elevated place. 



361. The practical utility of such classifications is easily 

 seen by comparing it with the address of a letter. So it is 

 with the naturalist, who, by his zoological classifications, 

 arrives speedily to the groups to which the animal belongs. 

 If, for example, he was desirous to define a hare, without 

 resorting to such means he would be forced to compare his 

 description to that of more than one hundred thousand ctif- 

 ferent animals. But if he says that the hare is a Vertebrate 

 animal of the class Mammalia, of the order Rodentia, of the 

 genus Lepus, by the first he excludes all invertebrates from 

 his comparison; by the second, he excludes all reptiles, fishes, 

 and birds; by the third, he distinguishes the hare from nine- 

 tenths of these mammals ; and having thus arrived at the 

 genus to which it belongs, a very few distinguishing cha- 

 racters in addition will enable him to characterize the species 

 for certainty. 



362. Artificial and Natural Classifications. Zoolo- 

 gical classifications are of two kinds, artificial and natural. 

 In the artificial classification of animals, the divisions are 

 based on modifications which certain parts of the bodies 

 present, and which are chosen arbitrarily ; in the natural 

 classification, on the contrary, the whole of the organization 

 of each being is taken into consideration, and then arranged 

 accordingly. 



363. An artificial system is generally of easy applica^ 

 tion, but it often gives us no important information but the 

 name of the object. Suppose we take the number of the 

 limbs as a base for classification, we should place in the divi- 

 sion quadrupeds the ox, the frog, the lizard, &c., thus 



