PKIMAEY DIVISIONS AND CLASSES. 207 



same principles into embr (incitements, 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, by 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 

 which its organization offers of most importance, since it is 

 in fact these very peculiarities which serve to characterize 

 these successive divisions. Now, we repeat, the functions and 

 manners of an animal are always dependent on the mode of 

 conformation of its organs, or at least in harmony with its 

 structure, and that consequently we may deduce from this 

 knowledge all the most important points in the history of the 

 species submitted to our investigations. 



Such are the bases on which rest the zoological classifi- 

 cations called natural. Let us now see what have been the 

 results of the application of these principles to the methodical 

 distribution of animals, and let us study the principal groups 

 formed by these beings. 



BASES OF THE DIVISION OF THE ANIMAL KINGDOM INTO 

 PEIMAKY DIVISIONS (SUB-KINGDOMS) AND CLASSES. 



372. Primary Divisions. Four general plans of struc- 

 ture, modified in a thousand ways, seem to have served as 

 guides for the creation of the animal kingdom. These four 

 principal forms may be understood by a reference to four 



