344 W. von BUDDENBROCK 



important characteristic of the tropism theory, and also, that 

 in direct consequence of this, according to the theory, the turn- 

 ing of the animal must always be around an axis which lies in 

 the plane of symmetry that separates the two body halves. 



A second, perhaps even more important characteristic of the 

 theory is the complete disregard of special structure, which sim- 

 ply does not exist for Loeb and his followers. We need know 

 only that the organism is symmetrical, — the theory is just as 

 applicable to protozoa or larvae of the simplest structure as 

 to the most complicated Metazoa — and that the organism reacts 

 to the particular energy; all else accounts for itself. Whoever 

 reads Loeb's writings might readily conclude, from different 

 expressions that are found here and there throughout, that he 

 is fighting against the conception that regards the actions even 

 of the lower animals* as voluntary acts of the will, and denies 

 that they are involuntary. This, of course, is not the case, and 

 is meaningless. Involuntary action is an undeniable fact of 

 observation, which expresses itself in the phenomenon that 

 under definite conditions all individuals of a species do the 

 same thing; no one questions the existence of involuntary action, 

 even though he may hold the view that not all the actions of 

 the lower animals are involuntary. 



Loeb has rather set himself the task of explaining the mechan- 

 ism of this involuntary action and by factors that work mechan- 

 ically. He attacks those who would explain the action by other 

 means; above all he objects to the conception of tropisms — and 

 especially of reflexes — as originally individual actions which have 

 shown themselves to be useful and in the course of time through 

 habit and inheritance have become mechanical and involuntary. 



For a thorough understanding of the following criticism this 

 view of Loeb's must be kept clearly in mind. 



OUTLINE OF THE ARGUMENTS AGAINST THE TROPISM THEORY 



To refute the tropism theory three lines of argument will 

 be advanced: 



1. We shall first show that the theory cannot explain all 

 tropisms, for two reasons, (a) in many cases the necessary con- 

 dition premised by the theory — namely, energy rays — may be 

 absent, and yet actual tropisms occur; (b) in other cases, al- 



