n THE CLASSIFICATION OF MAN. 93 



blcs them as they resemble one another — he dif- 

 fers from them as they differ from one another. 

 — And, though these differences and resemblances 

 cannot be weighed and measured, their value may 

 be readily estimated; the scale or standard of 

 judgment, touching that value being afforded and 

 expressed by the system of classification of ani- 

 mals now current among zoologists. 



A careful study of the resemblances and dif- 

 ferences presented by animals has, in fact, led 

 naturalists to arrange them into groups, or 

 assemblages, all the members of each group 

 presenting a certain amount of definable resem- 

 blance, and the number of points of similarity be- 

 ing smaller as the group is larger and vice versa. 

 Thus, all creatures which agree only in present- 

 ing the few distinctive marks of animality form 

 the Kingdom Animalia. The numerous animals 

 which agree only in possessing the special char- 

 acters of Vertebrates form one Sub-kingdom of this 

 Kingdom. Then the Sub-kingdom Vertebrata 

 is subdivided into the five Classes, Fishes, Am- 

 phibians, Reptiles, Birds, and Mammals, and these 

 into smaller groups called Orders; these into 

 Families and Genera; while the last are finally 

 broken up into the smallest assemblages, which 

 are distinguished by the possession of constant, 

 not-sexual, characters. These ultimate groups are 

 Species. 



Every year tends to bring about a greater uni- 



