16 STUDIES IN GENERAL PHYSIOLOGY 



the latter are concerned, it is wrong, as we shall see, to say 

 that certain animals "are fond of the light" and seek those 

 regions in space where light is most intense, while others "are 

 fond of the dark" and betake themselves to those regions 

 which are darkest. In contradiction of this idea I shall 

 prove that the direction of the progressive heliotropic move- 

 ments of animals is determined solely by the direction of the 

 rays, no matter whether the animals move from regions in 

 which light is less intense to those in which it is more 

 intense, or vice versa. 



Further than this, it is fundamentally wrong to say that 

 an assumed "preference for color" determines the orientation 

 of animals toward rays of different ref rangibilities ; that, 

 as Graber says, the animals which "are fond of blue" "hate 

 red," and that those which "are fond of red" "hate blue." 

 In contradiction of this iclea I shall prove that there are no 

 animals which "are fond of" red or "hate" blue, but only 

 such as move toward a source of light or away from it ; and 

 that these movements occur in the same way under the 

 influence of the more refrangible rays as under that of the 

 less refrangible rays, only with this purely quantitative 

 difference, that the more refrangible rays, as in plants, are 

 much more effective than the less refrangible ones, which 

 usually have no effect. 



I consider it inadvisable to represent the movements ob- 

 served in animals as the expression of a "color preference," 

 or a "color sensation," of a "pleasurable" or "unpleasur- 

 able sensation," as do most animal physiologists and zoolo- 

 gists who have studied the effects of light in the animal 

 kingdom. I do not propose to base an analysis of the 

 movements of animals on such hypothetical, anthropomorphic 

 sensations and feelings, but on such conditions as determine 

 the course of phenomena in inanimate nature as well. Real 

 natural science began when, instead of fabulizing over the 



