Tropisms Relation to Modes of Behavior 51 



subject stands almost without a rival in the history 

 of the science. 



Notwithstanding the work of Spencer, genetic 

 psychology was given perhaps its greatest impetus 

 by Darwin, not only through his influence in estab- 

 lishing the general doctrine of organic evolution, but 

 also through his careful work on, and illuminating 

 treatment of the mental life of animals. The admir- 

 able and original chapter on Instinct in the Origin 

 of Species, the chapters on the comparison of the 

 mental powers of man and the lower animals in the 

 Descent of Man, and the work on The Expression of 

 the Emotions in Man and Animals, were all sub- 

 stantial contributions to the science, which were very 

 influential in stimulating further work. 



It is not my intention to treat of studies of animal 

 behavior undertaken from the standpoint of evolu- 

 tion, but to discuss another and in many respects com- 

 plementary aspect of the subject, that of analysis, or 

 the effort to discover the causal mechanism of animal 

 activities by resolving them into their component fac- 

 tors. The analytical study of behavior is simply a 

 consequence of extending to animal psychology the 

 methods of experimental investigation so largely em- 

 ployed in the physical sciences and which are coming 

 more and more to be employed in biology and in the 

 laboratory investigations of the psychology of man. 

 The results thus far won may be meagre, but judg- 

 ing from the increasing number of trained investiga- 

 tors who are devoting themselves to the work, we 



