CHAPTER XIX 

 THE ORIGIN OF SPECIES 



Thoughtful men, once escaped from the blinding influences of 

 traditional prejudice, will find in the lowly stock whence Man 

 has sprung, the best evidence of the splendor of his capacities; 

 and will discern in his long progress through the Past, a reason- 

 able ground of faith in his attainment of a nobler Future. 



Huxley. 



EVERYONE recognizes not only that there are many kinds 

 of animals and plants, but also that many individuals are 

 essentially the same. Groups may be formed of individuals 

 which differ less among themselves in the sum of their char- 

 acters than they do from the members of any other group 

 of individuals. And further, the members of a group produce 

 other individuals which are essentially similar. Such a 

 group of similar individuals is termed by the biologist a 

 SPECIES. It will be noted, therefore, that a species is merely 

 a concept of the human mind the only reality in nature 

 is the individual, and an understanding of the differences be- 

 tween individuals gives us the key to the differences between 

 species. This seemingly obvious point of view has but 

 relatively recently been clearly emphasized by biologists, and 

 the species rather than the individual has loomed large 

 in the discussions of how plants and animals came to be what 

 they are to-day. 



From the time of the Greek natural philosophers there 

 always have been men who have sought a naturalistic expla- 

 nation of the origin of the diverse forms of animals and plants, 



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