24 LIGHT AND THE BEHAVIOR OF ORGANISMS 



of animal instinct and will." The author assumed that 

 these agencies had been fairly definitely ascertained with 

 reference to plants, and it was generally conceded that 

 their movements were not influenced by psychic phenomena. 

 He therefore began his work by attempting to show that 

 the reactions in plants and animals are controlled by the 

 same agencies, with the express purpose of proving that the 

 reactions of animals are not due to subjective (anthropo- 

 morphic) sensations as the work of Bert, Graber, Lubbock, 

 Romanes and others might lead one to infer. " I consider 

 it inadvisable," he says (1905, p. 16), ''to represent the 

 movements observed in animals as the expression of a 

 'color preference', or a 'color sensation', of a 'pleasurable' 

 or 'unpleasurable sensation', as do most animal physiolo- 

 gists and zoologists who have studied the effects of light in 

 the animal kingdom." (1906, p. 125), " It seemed to me 

 that we had no right to see in this tendency of animals to fly 

 into flame the expression of an emotion, but that this might 

 be a purely mechanical or compulsory effect of the light, 

 identical with the heliotropic curvature observed in plants. 

 I believed that the essential effect of the light upon these 

 animals might consist in a compulsory automatic turning 

 of the head toward the source of light, corresponding to the 

 turning of the head, or the tip, of a plant stem toward the 

 light; and that the process of moving toward the source of 

 light was only a secondary phenomenon. It seemed to me 

 also that if the stem of the plant could suddenly acquire 

 the power of locomotion, it would act exactly like the 

 animals which fly into the flame." 



In his first paper Loeb deals with the reactions of certain 

 insect larvae. He found that positive larvae go toward 

 the light even when conditions are so arranged that in so 

 doing they must go into light of lower intensity. These 

 results lead to the following conclusions (1888, p. 2): " Die 

 Orientirung der Thiere gegen eine Lichtquelle wird bei den 

 Pflanzen (J. v. Sachs) bedingt durch die Richtung, in 

 welcher die Lichtstrahlen die thierischen Gewebe durchset- 



