146 The Animal Mind 



la ting efficiency of differently colored rays. Mast (474), 

 using this method, found that some animal forms, such as 

 the larvae of the blowfly, are most strongly stimulated by 

 that region of the spectrum which acts most strongly on 

 the color-blind human being; others, such as the earth- 

 worm and the larvae of the worm Arenicola, were most 

 responsive to blue, as plants are. We shall later note the 

 significance which Loeb ascribes to resemblances between 

 plant and animal responses to light. 



Amoeba, which as we have seen reacts to a change of 

 light intensity by a checking of movement at the point 

 affected, appears when tested by light passed through 

 differently colored filters to react in the majority of cases 

 most markedly to blue, although there are individual 

 variations : some individuals respond most definitely to 

 violet, others to green or yellow, and still others to red 

 (467). The difference is merely in degree of response, and 

 we can infer nothing about a qualitative differentiation of 

 conscious accompaniments. In Hydra, which comes to 

 rest in moderately illuminated regions, blue and green light 

 seem to be a better substitute for white light than are red 

 and yellow (791). Schmid (661) says that red and yellow 

 affect the sea-anemone Cereactis aurantiaca differently from 

 blue and green, but does not state wherein the difference 

 consists. 



Graber (266) attempted to test the color discriminations 

 of a great many different animal forms by observing their 

 preferences for differently colored lights. As we have al- 

 ready seen, where an animal displays no preference or choice 

 between two stimuli, it by no means follows that the 

 stimuli are not discriminated : they may produce differ- 

 ent sensation qualities which are equally agreeable or 

 disagreeable to the animal. When earthworms were the 



