196 ZOOLOGY. 



Sometimes the species differs considerably from all others ; 

 but in general there exists a number more or less considerable 

 which strongly resemble each other, and which are only 

 distinguished by differences of little importance ; such as the 

 horse and the ass, the dog and the wolf. For natural 

 classifications, these closely allied species are reunited into 

 groups called genera, and to their specific name a generic 

 name is also added, common to them all ; thus we say the 

 grey lizard, the spotted lizard, the ocellated, &c., to designate 

 different species of the genus lizard ; and brown bear, white 

 bear, &c., for the different animals of the genus bear. 

 Genera which resemble each other are grouped together by 

 the name of tribe, or natural family. 



If we afterwards consider the structure of animals in a 

 more general way, we cannot fail to recognise in several 

 families the same dominating characters, thus giving to them, 

 in spite of their differences, a certain common character. In 

 this way the naturalist forms divisions of a more elevated 

 rank, which he calls orders, and reunites in turn these 

 orders into groups still more numerous, called classes. 

 But the classes themselves admit of being divided by the 

 same principles into embranchements, or primary divisions of 

 the animal kingdom. 



371. Thus the animal kingdom is divided into primary 

 divisions, these divisions into classes, the classes into orders, 

 the orders into families, the families into genera, and the genera 

 into species ; sometimes we are even obliged to multiply these 

 sections, but the principles are always the same ; the differ- 

 ences which exist between two classes ought to be more 

 important than those existing between two families, as the 

 characters of families ought to have a greater value than the 

 characters of the genera out of which these families are com- 

 posed. Thus it is the more important differences which 

 serve for the establishment of the primary division, those of 

 less importance which constitute the basis for the subdivision 

 of these into classes, and so on, until we arrive at species or 

 groups, formed, as we have already said, bv the assemblage of 

 all the individuals closely resembling each other, and which 

 may unite to perpetuate their race. 



It is evident then, in order to class any animal in the pri- 

 mary division, the class, order, family, genus, and species to 

 which it belongs must first be determined, and that by this 

 determination alone we obtain precise ideas respecting all 



