56 MIND IN EVOLUTION CHAP, iv 



molecular relations of protoplasm, whether in its undifferen- 

 tiated form or as later in the highly conductile form of 

 nerve fibres. The preponderance of a certain type of 

 action therefore means the prevalence of a certain structure. 

 In this way structures are built up under the influence of 

 natural selection so planned that a stimulus of a given kind 

 inevitably produces a certain reaction. Such a reaction is a 

 reflex. It is mechanical in so far that it is the result of a 

 pre-existing structure which acts uniformly in response to 

 stimuli of a particular kind. Though it produces a certain 

 result, it is not the fact that it will produce the particular 

 result which brings it into being, but the fact that similar 

 actions have in the past produced similar results. It is 

 thus a consequence, not a means. It is also in some degree 

 mechanical in another sense, viz., that it is in part 

 independent of the rest of the organism and its condition. 

 But that is a matter of degree, and we get many variations 

 from the extreme type in which a reflex appears to go on 

 quite independently of the organic life, up to cases in 

 which it is dependent on the general state of the organism, 

 and may be subordinated to some higher type of activity. 

 This interdependence gives occasion for ambiguity in the 

 interpretation of special classes of action, but in no 

 way obscures the principle on which the classification 

 depends. 



