HELIOTROPISM OF ANIMALS 81 



desire to examine the new and striking object;" and then 

 quotes some remarks which he found in the manuscripts of 

 Darwin: "Query: Why do moths and certain gnats fly into 

 candles, but not into the moon when the same is at the hori- 

 zon ? I noticed long ago that they fly much less frequently 

 into candles on a moonlight night. When a cloud passes 

 over the moon, they are again attracted by the candle." 

 Romanes believes that: " The answer must be that the moon 

 is a familiar object, which insects consider as a matter of 

 course, and so have no desire to examine it." 



As we have seen, it is not the "new and striking" object 

 and "the desire to examine it" which drive the insects to 

 the lamp, for they are attracted, as I have shown, also by 

 the natural source of light, the sun. No reason seems to 

 exist to my mind for believing that the moon is a more 

 familiar object to the insects than the sun. I cannot well 

 see, however, how Romanes harmonizes the phenomena of 

 negative heliotropism in animals with "the desire to examine 

 unfamiliar objects." The history of science has taught us 

 that confusion always reigns when anthropomorphic motives 

 are brought into scientific research. Before the time of 

 Galileo a body sinking in a fluid "sought its place." 1 Galileo 

 and his followers put an end to the sovereignty of this 

 psychology, at least in inanimate nature. Mankind has had 

 no reason to regret this revolution. In biology, however, 

 even at this date, protoplasmic substances still move toward 

 the source of light "because of curiosity." 



XIII. SUMMARY OF RESULTS 



I shall conclude by summarizing the more important 

 results of my investigation: 



I. The dependence of animal movements on light is in 

 every point the same as the dependence of plant movements 

 on the same source of stimulation. 



1 See MACH, GZschichte der Mechanik, 1st ed., p. 117. 



