THE EVOLUTION OF ANTS 



(species) , some of which are very similar, though distinct — 

 such as the various kinds of oaks, pines, deer, and ducks — and 

 even the superficial observer knows that these species, though 

 they may be very constant in many of their characteristics, 

 are nevertheless more or less variable in others. And third, 

 everybody knows that many of our breeds of domesticated 

 animals and plants have given rise and are still giving rise 

 under human control to other breeds, some of which show 

 great differences from their ancestors, such as those, for 

 example, seen among our dogs, pigeons, roses, and grapes. 

 The facts of the first and the third group we can observe 

 directly; those of the second group, showing classification, 

 require explanation. 



The resemblances and the differences between the kinds of 

 animals and plants might be accounted for in two ways: 

 either these several kinds were created independently, simul- 

 taneously or successively, or they were derived by natural 

 descent from common ancestors, in the same manner as the 

 various breeds of domestic animals and plants were derived 

 from their ancestral forms. The first explanation is super- 

 natural and nongenetic; the second is natural and genetic. 

 There is no question as to which of these explanations the 

 scientist and the philosopher must prefer, for, as Joseph 

 McCabe says, 'no plea for the supernatural origin of any- 

 thing is valid so long as there is a possibility of a natural 

 explanation of its origin/' 



The changes noted in the three groups of facts discrimi- 

 nated above all come under the head of "development" in its 

 general sense, but those of the first group comprise the 

 development of individual organisms, whereas those of the 

 second and third comprise the development of races. The 

 term "development," or "ontogeny," is now commonly used 

 of individual development; the terms "evolution," or 



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