THE WORLD OF LIVING ORGANISMS 141 



brought to a standstill at the very outset. It should be 

 emphasised, however, that the Germans are the only investi- 

 gators who have remained conscious of the difficulty of their 

 task. The experiments by Americans are far too crude to be 

 taken seriously. It is far from obvious why a triangle or a 

 circle should serve as the basis of the first experiments to 

 determine form-perception in an animal such as a bee, which 

 has to distinguish the outlines of flowers ; and, as Fritsch has 

 pointed out, this points to a complete misunderstanding of 

 the biological problems. 



Investigation of indications can be successful only when we ^ 

 have analysed the various responses of an animal within the 

 setting of its normal life, for the difference in response affords 

 us the most reliable clue to the differences between indications. 



The circle and the triangle are symbols from plane 

 geometry, which are constructed from our subjective 

 direction-signs ; and they have nothing to do with the 

 possibly recognisable outlines of the objects that are of 

 importance for certain function-circles of certain animals, 

 and there find application as indications. 



If it is important for an insect to be able to recognise 

 a certain enemy a long way off, it may be that the outline 

 of this enemy alone serves as indication, and that no other 

 outline in the world would so serve, although to us it might 

 appear much simpler. 



We must note, however, that the sureness with which 

 flying insects avoid twigs and leaves does not at all impl}^ 

 that the outlines of these serve as indications. Whatever 

 form they present, they one and all act merely as the same 

 indication, namely, an obstacle. 



If we want to get reliable information concerning form- 

 perception, we must start from the form-signs and colour- 

 signs of the objects that are the animal's prey or enemies, 

 or from those signs in the males at the breeding-season. For 



