ORGANIC MOVEMENTS 41 



gained by the work of Loeb, and it is from this point that 

 a purely analytical treatment of the theory of instincts must 

 start. By resolving all instincts into chain-reflexes that as 

 a whole were of the well-known character of " taxis," Loeb 

 implicitly had stated a very important problem in the form 

 of a fact : science in the future will have to find out 

 whether there is any such fact. 



B. THE PEOBLEM OF THE STIMULI OF INSTINCTS 



If indeed all instincts are of the type of very simple 

 co-ordinated motions, whether that be the most simple and 

 merely additive type or any more complicated one in short, 

 if all instincts as a whole are of the character of a " taxis," 

 it follows that it only can be the simple and elemental 

 agents in Nature which can act as stimuli to instincts. The 

 stimuli of instinctive movements may be light of different 

 wave-lengths, or heat, or moisture, or chemical compounds, 

 but they never are specific typical bodies. 



It will soon appear how important this statement is. 

 If only simple stimuli are concerned in instinctive life, the 

 relation between the medium and the instinct may easily be 

 explained on the analogy of a machine, at least in principle. 

 But what are we to say if typical complicated stimuli, if 

 " individualised " stimuli, as we shall call them, also awaken 

 instinctive movements ? 



Let us first try to show, by the aid of a simple instance, 

 what is meant by our two contrasted classes of stimuli : 

 Lloyd Morgan l performed a series of very fine experiments 

 in order to show whether chickens, just hatched from the 



1 Habit and Instinct, London, 1896. 



