THE HISTORY OF MENTAL DEVELOPMENT 133 



The dawn of this much of intelligence far down in the 

 animal kingdom would not be surprising, for the 

 selection and grasping of food has always involved 

 higher mental power than most of the actions of these 

 lowest animals. Memory goes far down in the animal 

 kingdom. Perhaps, as Professor Haeckel has urged, 

 it is an ultimate mental property of protoplasm. And 

 the memory of past experience would continually tend 

 to modify habit or instinct. 



It is unsafe, therefore, to say just where intelligence 

 begins. A.t a certain point we find dim traces of it ; 

 below that we have failed to find them. But that 

 they will not be found, we dare not affirm. In the 

 highest insects instinct predominates, but marks of in- 

 telligence are fairly abundant. Ants and wasps modify 

 their habits to suit emergencies which instinct alone 

 could hardly cope with. Bees learn to use grafting wax 

 instead of propolis to stop the chinks in their hives, 

 and soon cease to store up honey in a warm climate. 



Our knowledge of vertebrate psychology is not yet 

 sufficient to give a history of the struggle for suprem- 

 acy between instinct and intelligence, between inher- 

 ited tendency and the consciousness of the individual. 

 But the outcome is evident ; intelligence prevails, in- 

 stinct wanes. The actions of the young may be purely 

 instinctive ; it is better that they should be. But in- 

 stinct in the adult is more and more modified by 

 intelligence gained by experience. There is perhaps 

 no more characteristic instinct than the habit of nest- 

 building in birds. And yet there are numerous in- 

 stances where the structure and position of nests have 

 been completely changed to suit new circumstances. 

 And the view that this habit is a pure instinct, un- 



