{Authors are responsible for nomenclature used.) A 





The Scottish Naturalist 



No. 65.] 1917 [May. 



THE PROBLEM OF ADAPTATION. 



To any student of animal life it is clear that, as a whole, 

 animals are remarkably well fitted each for its own particular 

 surroundings and mode of life. The question has often been 

 asked, by what means this more than casual fitness has come 

 about, and one of three answers has been the rule. One 

 type of mind sees nothing for it but that each creature must 

 have arisen as it stands, a perfect and finished work of art. 

 The more modern points of view hinge round two different 

 aspects of the problem of an adaptation gradually reached 

 through stages of natural evolution. To the one, nature, 

 that is to say the external environment, is the chief agent in 

 the process, continually cutting off the possessors of such 

 variations as do not help to reduce the discord between an 

 animal and its surroundings, so that in the end the well- 

 adapted animals are just those which have been spared. In 

 this view, which depends mainly on the trivial variations 

 universally present in living things, the importance of the 

 animal organism as a directive force is reduced to a minimum. 

 To the other view the organism itself is the main controller 

 of its evolution : new needs and new desires bring new 

 adaptations in their train. 



In these two views, the one negative, the other positive, 

 as regards the animals' activities, are typified two modes of 

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