24 Habit and Instinct. 



through experience, and are thus not of ancestral, but 

 of individual origin. The one group comprise congenital 

 activities; the other group, acquired activities. And 

 whether the definiteness individually acquired in one 

 generation contributes to the definiteness of ancestral 

 origin in succeeding generations, is the subject of discus- 

 sion among biologists. 



It must not be supposed that the distinction between 

 what is congenital and what is acquired — a distinction 

 which we are endeavouring to draw with the utmost clear- 

 ness — is invalidated by the fact that there are a great 

 number of activities, such, for example, as the perfected 

 flight of birds, which are of double origin, being in part 

 congenital and in part acquired. Such cases do indeed 

 show that imperfect instincts may be perfected by habit 

 and individual acquisition of skill. But they render the 

 more necessary a careful distinction between the factors 

 which co-operate to produce the ultimate result. And 

 only when the distinction is thus duly emphasized does the 

 question, whether the acquired perfection of one generation 

 tends to lessen the congenital imperfection in the next 

 generation, stand out in its true significance. It is interest- 

 ing here to compare the flight of birds with the flight of 

 insects. In the latter class we find many cases in which 

 the instinctive factor in flight is relatively much more 

 highly developed towards congenital perfection than it is 

 in the former class, at any rate so far as most birds are 

 concerned. The question therefore arises, Is the greater 

 relative perfection in the instinctive flight of some insects 

 due to the inheritance of acquired skill on the part of their 

 ancestors? Or is it due to the fact that there has been 

 among insects more elimination of those who failed in 

 congenital power of flight, and hence a survival through 

 natural selection of those in which the instinctive flight 



