2l6 journal of Comparative Neurology and Psychology. 



lines of descent, and in numerous cases has been suffered to dis- 

 appear again. It leads animals now to lie quiet, and now to seek 

 safety in flight. These two aspects of the fear response are found in 

 different relative degrees of development in different forms. 

 Both are of service in escaping from enemies, although some- 

 times one is employed to greater advantage than the other. Fear 

 as it occurs in higher animals is a sort of combination of two 

 instinctive tendencies of a very different nature, but whose mani- 

 festations are brought about by similar situations. Often these 

 tendencies conflict and there results a state of indecision in which 

 neither finds its natural expression. In some animals only one 

 of these elements usually found in fear phenomena are present; 

 there is only one method of meeting the situation. Ranatra 

 shows only the element of deceptive quiet in the presence of its 

 enemies. Other insects whose reactions I have studied exhibit 

 no trace under any circumstances of the instinct to seek safety in 

 remaining quiet, but always make vigorous efforts to escape by 

 flight. Which of these instinctive responses develops doubtless 

 depends on the general mode of life of the animal and its habitual 

 environment. Where an animal possesses both, as most higher 

 forms do, there is opportunity for meeting different kinds of 

 situations with a more appropriate response. 



