266 MENTAL EVOLUTION IN ANIMALS. 



of instinctive habits, or to an originally conscious imitation 

 by one species of the instinctive habits of another. Lastly, 

 I have joined the two tree-like growths at their summits in 

 order to represent the fact that intelligent and non-intelligent 

 adaptation, or primary and secondary instincts, may fuse 

 together and then possess a common sap or principle of 

 further growth. I have also represented such union between 

 the two sides of the diagram, primary and secondary, to take 

 place at one other point — viz., between the branch Primary 

 Instinct and the branch Intelligent Variation of Secondary 

 Instinct. I do this to bring out into stronger prominence the 

 fact that when once a non-intelligent or primary instinct has 

 been formed, it is most ready to join with and become fertilised 

 by the principle of intelligence at any point where this 

 principle is, as it were, mobile, or not yet fixed and frozen 

 into secondary instinct. But the most important thing to 

 remember is that whether instincts have had an intelligent or 

 a non-intelligent mode of origin, they may at any time after 

 their full formation come into contact with intelligence at any 

 point ; so that the two sides of our diagram (being the 

 embodiment of all the foregoing evidence upon the subject) 

 illustrate at once the truth and the falsity of the common 

 opinion which has been so neatly rendered by Pope, when 

 he says of instinct and reason that they are things " for ever 

 separate, yet for ever near." 



I shall now proceed to give a general summary of all the 

 preceding chapters on Instinct. 



After defining the sense in which alone I use the word 

 Instinct, I proceeded to give a few illustrations of the perfec- 

 tion of instinct as exhibited by very young animals, or by 

 animals without individual experience of the circumstances 

 to which their instinctive actions are adapted. Next I gave 

 a few complementary illustrations of the imperfection of in- 

 stinct, and pointed out that such imperfection might arise, 

 either from a change in the conditions of the environment to 

 which the ancestral instinct was adapted, or from the fact that 

 the instinct is not yet completely formed. I also showed that 

 imperfection of instinct might arise from internal or psycho- 

 logical changes throwing out of gear the delicate mechanism 

 on which the perfect display of instinct depends. In this 

 connection I gave instances to prove that such derangement 



