EXAMINATION OF THE THEORIES OF OTHER WRITERS. 267 



of instinct is particularly apt to arise when the normal 

 history of an animal's converse with its environment is 

 interrupted for a time and again renewed. I also gave one 

 case of such derangement where there had been no sucli 

 interruption, and which, therefore, may most properly be 

 regarded as a case of insanity. 



If instincts are slowly evolved, we should expect to meet 

 with some cases in which they are not yet fully evolved, and, 

 as just observed, for this reason imperfect. Such cases we 

 do lind — as, for example, young turkeys pointing at tlies, 

 young chickens being half afraid of bees, rabbits only toddling 

 instead of running away from weasels, &c., &c. We may 

 also see instincts in course of development among young 

 children learning to balance the head, to walk, to speak, &c. 

 ]\Ioreover all cases of the education or improvement of in- 

 stinct, whether in the individual or in the race, are so many 

 cases of the original imperfection of instinct. But this 

 brought us directly into the question as to the origin of 

 instincts. 



I have endeavoured to prove that the origin of instincts 

 may be what I have called either primary or secondary. 

 That is to say, I believe there is ample evidence to show that 

 instincts may aiise either by natural selection fixing on pur- 

 poseless habits which chance to be profitable, so converting 

 these habits into instincts without intellisjence beincr ever 

 concerned in the process ; or by habits, originally intelligent, 

 becoming by repetition automatic. As an example of a 

 primary instinct I gave incubation; and as examples of 

 secondary instincts I gave sundry cases of " practice making 

 perfect." On a pnori grounds we saw that instincts must 

 arise by the processes thus explained, and then we proceeded 

 to render a ^posteriori proof that they have. This proof under- 

 took to show that purposeless habits occur in individuals, are 

 inherited, vary, have their variations inherited, and then 

 developed in beneficial lines by natural selection ; also that 

 habits originally intelligent by repetition become automatic, 

 and, having lapsed from intelligence, are then inherited as 

 instincts, which may then vary, have their variations inherited 

 and developed in beneficial lines by natural selection, as in 

 the previous and analogous case. These sundry proposi- 

 tions were substantiated by showing, first, that tricks of 

 manner are displayed more or less by every one, and especially 



