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THE AMERICAN NATURALIST [Vol. XLVII 



a machine standing still, we divest it of precisely that 

 element which is most distinctive of it. The anatomical 

 conception of an organism as a mechanism at rest, useful 

 and important as it lias been and is still, is thus funda- 

 mentally defective. The essential feature of every liv- 

 ing thing is incessant activity, and adaptations are part 



sive examples as the adaptation of a mothto the bark of 

 the tree on which it rests depends for success as much 

 on the position of the moth's body, the pose of its wings, 

 etc., all features of muscular action, as upon the color 

 pattern of the exposed parts. Thus adaptation, like 

 other truly organic phenomena, exhibits a fundamental 

 dependence on organic activity, a condition that favors 

 the conception of the organism as put forward long ago 

 by Lamarck. 



But adaptation is not only essentially associated with 

 the activities of organisms; it is also conditioned by the 

 continuity of this activity. Every organic line of descent 



sible future. The continuity thus indicated is an es- 



any moment be completely resolved into its elements and 



violating the law of its existence. But an organism can 

 not undergo such a revolution without annihilation; an 

 animal or plant subjected to such a process would cease 

 to exist. Hence life is not only activity; it is activity so 

 directed as to be continuous, to be self-perpetuating. 

 Continuity of action is, therefore, an inherent part of 

 the make-up of living things, and adaptation is condi- 

 tioned by this continuity in that those reactions are 

 adaptive which make for a continuance of life. 



than does a'speries; it is a word in the dictionary, a fig- 

 ment of the human brain. Just as the systematist finds 

 the individual animal or plant the real object of his in- 

 vestigation, so the student of adaptation finds individ- 



