CHAPTER XII 

 ADAPTATION 



In previous chapters we have considered the correlation of in- 

 heritance and environment in the determination of the organism, 

 and various specific instances of the resulting adaptation. These 

 things are of particular importance in the theories of evolutionary 

 processes. If species change and give rise to other species, the 

 results of their modification must be adaptations fitting the later 

 generations to some definite type of environment. We can hope to 

 understand the process of change only through extensive knowl- 

 edge of changes which have already come aliout, since the duration 

 of science has been too brief to afford us an actual view of evolu- 

 tion in progress. 



Adaptations : Process and Result. The process of adaptation, 

 for it is a process as well as a result, is visible in the lives of indi- 

 viduals, and is experienced by each of us. We spade the garden, 

 and blister our hands, but if we continue such work day after day 

 our palms form calluses which no ordinary amount of friction can 

 blister. We train for sports, and our strength or endurance or 

 skill increases day by day. After an athletic career in college we 

 return gradually to the less active round of business or professional 

 life, or suffer from a sudden change of habits. All of these things 

 are adaptive processes. 



In the individual adaptations can be observed as readily as the 

 activities which give rise to them. They fit each being into the 

 environment which he occupies, and whether they are mental or 

 physical, they are no less real. 



Adaptations are as conspicuous in all species, moreover, as they 

 are in its component individuals, but the processes which brought 

 them about are no longer evident. All animals of common ex- 

 perience show peculiar fitness for the lives which they lead. Squir- 

 rels have chisel-like teeth which are effective for opening nuts. 

 Similar teeth serve the beaver for cutting down trees, but the 

 beaver is otherwise fitted for swimming and the squirrel for climb- 

 ing trees. The fitness of the horse's teeth for grazing has been 



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