CONFORMITY WITH PLAN 



307 



and to transfer the rhythm of animal life entirely to the 

 exterior. 



There is an essential misconception here, for the tropisms 

 are not simple physical processes. The appearance of a 

 tropism, which by its nature remains a reflex, necessarily 

 presupposes the presence of an indication. It is true that an 

 indication crops up on the life-path of an animal only when 

 a stimulus affects the receptors. But it depends entirely 

 on the structure of these as to which stimulus is taken up 

 and converted into excitation. There is no physical law, pro- 

 ceeding from which we can say that such and such a physical 

 process must become an indication for the animal, while 

 such and such another one will not. Much less dare we assume 

 that some particular object must play a part in the life 

 of the animal also. We can only conjecture that it is an 

 indicator : what indications it gives depends solely on the 

 animal. 



The life-path of an animal, which we may imagine as a 

 tunnel of indications, holds only such things as exist through 

 their relations to the animal — those and no others. If we 

 wish to enter into the life-path of an earthworm, for instance, 

 we must not forget that it is composed of earthworm things, 

 and of nothing else. 



Nevertheless, the inquiry into the presence of an external 

 rhythm and its effect on the animal is justified. The observer 

 can show that the indicators appear on the life-path in a 

 sequence independent of the animal, and he may ask himself 

 the question, " In how far is an inner rhythm of the animal 

 opposed to the external rhythm ? " 



It must first be shown that the threshold value of the 

 external stimuli is determined by an inner rhythm based on a 

 periodic change in the steering-gear. Thus, for example, 

 an object will not act as an indication on a satiated animal, 

 though it certainly would on a hungry. In the same way. 



