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 



