58 DEVELOPMENT AND PURPOSE CHAP. 



aims at near results, which will relieve the tension and so 

 satisfy. From these it advances step by step till it grasps 

 the end of the instinct, which then becomes suffused with 

 purpose. 



Among the higher animals, but particularly among the 

 most developed insects, there are long trains of intricately 

 adjusted actions, which can be conclusively shown to be 

 independent of any intelligent apprehension of their ulti- 

 mate end, though they may use a measure of dawning intel- 

 ligence in the manner indicated in executing certain steps. 

 These form the instincts proper, and their genesis is to 

 be understood by the analogy of the reflex, i.e. as arising 

 through the accumulated effect of small variations, each 

 of which is serviceable to the species. In the case of the 

 reflex, what comes about is a structure adjusted so as to 

 respond to a sense stimulus in a manner which serves a 

 need. In the case of the instinct, the adjustment is more 

 complex. There is first a tension which continues or recurs 

 until a need is met, and secondly, an adjustment which 

 secures that this tension is at any given moment relieved 

 by the action which under the circumstances is in the train 

 tending to serve the need. The state of momentary 

 equilibrium or satisfaction, that is to say, is adjusted to 

 the appropriate combination of objects and actions. It 

 determines that sensori-motor adjustment which is in fact 

 required by the organic need, and as the tension is con- 

 stantly revived till the need is met it governs a train of 

 adjustments which are in the end successful. 1 Instinct 



1 Note here the development of conation involved in the evolution of 

 instinct. We saw above that conation was involved in the maintenance or 

 recovery of the optimum or equilibrium state in the presence of disturbing 

 causes. The term was justified on the ground that the reactions were 

 determined by the difference between the existing state of the organism 

 and another state, which they tend to introduce this other state being 

 one of * equilibrium.' In the case of instinct, the equilibrium itself is at 

 any moment a state of tension or conation. It is a state of excitement 

 dependent on the difference between the existing conditions of the 

 organism, and the conditions at the time when the instinct function 

 is complete, and through its effect on action at each moment it tends to 

 produce the state which terminates its activity. Conation develops then 

 from the determination of action by response to the equilibrium point, 

 to the determination of the equilibrium point itself by reference to 



