PART II 

 SYSTEMATIC ZOOLOGY 



CHAPTER XIV 

 THE CLASSIFICATION OF ANIMALS 



Basis and significance of classification. It is the 

 common 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 history, 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 resemblances 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 resemblances and differences, but later when 

 naturalists began to dissect animals and to get acquainted 



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