MOLLUSKS, ARTHROPODS AND VERTEBRATES 235 



given by Engelmann, Bert, Graber, Lubbock, Romanes, 

 Darwin and others, all of whom preceded Loeb, were 

 largely founded on this idea. 



(14) Light no doubt acts on organisms without a change 

 of intensity much as constant temperature does, making 

 them more or less active and inducing changes in the sense 

 of orientation; but there Is no conclusive evidence showing 

 that light acting thus ever functions In the process of 

 orientation. 



