Nest-building, Incubation, and Migration. 255 



experience that the trick is effectual ? All one can say is 

 that it would be experience perilously acquired. Granting 

 what I find it rather hard to grant, that the bird has the 

 wit to try the trick ; a little over-acting, a little too much 

 lameness of wing, and she is herself seized and killed ; a 

 little under-acting, and the trick fails, and the little ones 

 are killed. Does it not seem probable that such experience 

 would be dearly bought ; that failure would mean either 

 death to the parent or death to the offspring ? Is it not 

 clear that natural selection is thus introduced in any case ? 

 And may not the selectionist pertinently ask : Why, if 

 natural selection be thus introduced as a factor, halt 

 midway between two hypotheses? Why not take the 

 further step — one by which all the difficulties attending 

 the mode of intelligent origination are avoided — of allowing 

 that natural selection exercises, throughout, its influence on 

 congenital variations and not on acquired modifications of 

 faculty ? 



While admitting the logical cogency of this argument, 

 I cannot but think that, were the biological difficulties 

 attending the fact of transmission removed, such an 

 instinct as is shown by the lapwing or wild duck would 

 be best explained by a co-operation in some way of in- 

 telligence and natural selection. I shall have a suggestion 

 to make on this head at a later stage of our inquiry, 

 according to which modification may be a factor in race- 

 progress without direct transmission. The result of the 

 foregoing discussion is, I take it, that though the instinct 

 in question does not afford so strong a case in favour of 

 the inheritance of acquired characters as at first sight it 

 would seem to do, yet its development, in complete in- 

 dependence of intelligent guidance by the natural selection 

 of fortuitous variations, puts no inconsiderable strain on 

 the theory of the all-sufficiency of natural selection. As 



