CHAPTER X 

 THE ORIGIN OF SPECIES 



THE mutability of all organisms is universally 

 recognized by modern biologists, and the 

 origin of new types or " species," as the result of 

 such mutability, is no longer questioned. Many 

 attempts have been made to explain the mechanics 

 of the origin of species, and the laws governing 

 them; but none of the very divergent theories pro- 

 posed can be said to offer a satisfactory explanation 

 of all the facts concerned. 



Experimental Morphology. For a number of 

 years the efforts of many of the ablest biologists 

 have been devoted to what has been called experi- 

 mental morphology, or a study of the effects of vari- 

 ous stimuli upon the structures of organisms. It 

 becomes more and more evident that plants are as- 

 tonishingly plastic, and respond very quickly to 

 stimuli of many kinds which may exercise powerful 

 formative effects upon their structures. Plants, be- 

 ing especially adaptable, and generally more easily 

 handled than animals, have naturally received much 

 attention at the hands of the experimenter, and the 

 results of these studies have added much to our 

 knowledge of the laws governing the development 

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