358 W. von BUDDENBROCK 



the above statement, then in return we can assure him that we 

 regard the actions of lower animals just as he does, as involuntary, 

 and that for the most part we reject any idea of free will; he 

 must then discuss certain questions with us. 



For example: The eye of the heliotropic Balanus larva is of 

 little use in enjoying the beauty of the surrounding scenery; we 

 assert this because we, like Loeb, deny the larva's higher intel- 

 ligence and free will. In consequence, we are forced to the view 

 that the purpose of the eye, for it must have some purpose, is 

 to enable the heliotropic reflex to take place, at least we know 

 of nothing else for which the eye might serve. It therefore fol- 

 lows that the entire reflex arc, which alone it is that makes the 

 eye capable of functioning, is purposeful. In going so far we 

 finally cannot escape the view that the cause of the tropism is 

 just this mechanism of the reflex arc, so adaptive in construc- 

 tion and in function, and that energy plays no other role than 

 to set the apparatus in motion. 



If Loeb replies to this deduction that all tropisms must then 

 have a biological use, the following is my answer: The contrary 

 assertion is in no way proved ; if in many cases the tropism seems 

 useless or even harmful for the animal, it is highly probable that 

 we either do not understand what its use is, for we know pain- 

 fully little of the normal needs of the lower animals, 13 or it may 

 be, that during the experiment the experimenter has kept the 

 animal under unnatural conditions, a case that is only too 

 frequent. 



To condense and recapitulate the foregoing argument: The 

 facts are, that light, with the help of the eye and the associated 

 reflex arc, starts a definite movement, of which light is one 

 condition, the reflex arc the other condition of its occurrence. 

 No conclusion can be reached from this statement, either for 

 or against the tropism theory. The latter theory acquires mean- 

 ing only when to the facts we add a definite definition of the 

 expression " animal," defining it simply as a form with definite 

 chemo-physical structure, without any reference to the purpose- 

 ful nature of its structure. Upon this form, then, the blind 

 natural orce acts ust as iron upon a magnetic needle, and so 



13 A more detailed consideration of this point would carry us too far. I will, 

 however, call attention to the valuable work of Franz, "Die phototaktischen Er- 

 scheinungen im Tierreiche und ihre Rolle im Freileben der Tiere," Zool. Jahrb., 

 AM. f. allg. Zool, Bd. 33, 1914. 



