CHAPTER V. 



NERVOUS ACTIVITY AND ALSO DEVELOPMENT DEPEND- 

 ENT ON ASSOCIATION AND REPETITION. 



While investigating the causes of evolution it 

 is always necessary to bear in mind the complex 

 character of living matter. We must remember 

 that in addition to those of its properties which 

 may be visibly observed in its natural state and 

 under experiment, and those which may be proved 

 by chemistry, and those which it possesses in com- 

 mon with certain inanimate bodies, it also has one 

 other essential property, namely, that which is 

 expressed in its capacity for development. Not 

 only has this capacity been the sustaining basis 

 of the whole evolution of the various forms of life 

 from the amoeboid up to man, but it allows the 

 process of evolution to be constantly repeated — 

 more or less imperfectly, — in each individual life. 

 A consideration of protoplasm from this point of 

 view, with a full appreciation of this fact, is neces- 

 sary to a well-rounded conception of the fundamental 



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