PART III 



DIFFERENT KINDS OF ANIMALS, THEIR 



CLASSIFICATION, HABITS AND 



SPECIAL RELATION TO MAN 



CHAPTER X 

 THE CLASSIFICATION OF ANIMALS 



Basis and significance of classification. — It is the com- 

 mon knowledge of all of us that animals are classified: 

 that is, that the different kinds are arranged in the mind 

 of the zoologist and in the books of natural histroy, in various 

 groups, and that these various groups are of different rank 

 or degree of comprehensiveness. A group of high rank 

 or great comprehensiveness includes groups of lower rank, 

 and each of these includes groups of still lower rank, and 

 so on, for several degrees. For example, we have already 

 learned that the toad belongs to the great group of back- 

 boned animals, the Vertebrates, as the group is called. 

 So do the fishes and the birds, the reptiles and the mammals 

 or quadrupeds. But each of these constitutes a lesser 

 group, and each may in turn be subdivided into still lesser 

 groups. 



In the early days of the study of animals and plants their 

 classification or division into groups was based on the re- 

 semblances and the differences which the early naturalists 

 found among the organisms they knew. At first all of the 

 classifying was done by paying attention to external re- 



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