ORGANIC MOVEMENTS 43 



Now it is very important to notice that, if an actual case 

 of a specific individualised stimulus of an instinct should 

 become known, the limits of the possibility of a mechanical 

 explanation would be exceeded. They would be exceeded, and 

 an autonomic or vitalistic factor would be at work, because 

 it could by no means be understood how the specifically 

 combined or " individualised " stimulus could be received by 

 the organism in such a way as to become the cause of a 

 specific and fixed series of motions in the organism. Sup- 

 posing that any organism were specifically affected in its 

 instinctive movements by the mere sight of any other 

 typical organism, say of the same species but of the other 

 sex, 1 and that this affection were the same, whether the 

 organism which forms the stimulus were seen from before 

 or from behind, or from the side and at any angle whatever : 

 what would follow from such a fact ? A machine could 

 only be fitted to receive the specific complicated stimulus 

 in a few typical positions, but how could a machine be 

 imaginable if an infinite variety of aspects had the same 

 invariable instinctive effect ? 



We may stop our discussion at this point, as a very 



which are only relatively determined, and its reaction is perfect for the very 

 first time, that is, instinctive. New researches are required to clear up the 

 facts that come into account here. 



Chickens are well known to peck their peas or corn with a right calcula- 

 tion concerning the dimension of depth the very first time they do peck. 

 Speaking psychologically : the right idea of space is innate in them not only 

 " a priori," in the sense of Kant, but strictly "before" all experience in the 

 temporal sense of the word "before." 



Are these facts of use in our present problem ? 



1 As regards sexuality the existence of "individualised" stimuli of 

 instincts seems indeed highly probable. Male moths deprived of their wings 

 were found by Mayer-Soule (Journ. exp. Zool. 3, 1906) not to be admitted to 

 copulation by the females ; but only if the females were not deprived of 

 their sight ! 



