238 'Journal of Comparative Neurology and Psychology. 



the result of movements which are determined by the structure and internal 

 states of the organism, rather than by external conditions. The facts presented 

 by BoHN make it apparent that there is more than one mode of orientation, and 

 that no single theory at present accounts for all the observed facts. It is interest- 

 ing to note that BoHN distinguishes two forms of reaction to light, and makes use 

 of the terms phototaxie and phototactisme in the senses in which certain papers 

 have used phototaxis and photopathy. 



The chief value of the papers, which we have been discussing, is their stimulat- 

 ing influence. They are not thoroughly satisfactory scientifically* for they con- 

 stantly suggest questions, doubts and new problems; yet just because of this, the 

 reader leaves them with new interest in the problems of animal behavior and 

 increased enthusiasm for investigation. 



ROBERT M. YERKES. 



