204 Heredity and Social Progress 



destroy the mental associations by which the 

 acquired characters are linked. I doubt if con- 

 tests now go far enough to eliminate natural 

 characters. These are brought into accord 

 with their environment of acquired characters 

 and of acquired organs by emotional changes 

 that cut back and then permit regeneration to 

 develop a form harmonizing with the new 

 conditions. Emotion is thus the agent of har- 

 mony between the various natural and acquired 

 organs. It modifies but does not destroy. 

 Selection results from destruction, but in the 

 case of man it is the destruction of mechan- 

 isms and not life. Human progress is not 

 therefore due solely to the action of selection. 

 The play of emotion is equally effective, and 

 in the case of natural characters it is per- 

 haps the sole agent of progress. 



Progress in man is by differentiation and is 

 a problem of equilibrium. There are no addi- 

 tions to the elements of cell life. When they 

 change it is by a differentiation from a neu- 

 tral centre, which creates an equilibrium by 

 means of the utilization of both differenti- 

 ated parts. Modifications of structure in one 



