Nest-building, Incubation, and Migration. 253 



acquisition by the individual, on the one hand, and the 

 natural selection of congenital variations, on the other 

 hand, are both working, in their different spheres, towards 

 the same end that of adaptation. This is their common 

 goal ; but they endeavour to reach it by different routes. 

 "Well, then, suppose they do reach the goal, the one by 

 intelligent adaptation, the other by organic adaptation, 

 is this to be wondered at ? Is it a coincidence in any 

 proper sense of the term ? Surely not. If two men start 

 for the same place, the one by sea and the other by land, 

 we should not regard it as a coincidence if both got there. 

 If acquired adaptation and congenital adaptation reach 

 the same end by different methods, this is due to the fact 

 that the result is adaptive, and is what nature in either 

 case is really all the while aiming at. Natural selection, 

 too, in any such cases, is permitting the survival of those 

 who, whether by the application of purely individual 

 intelligence, or by congenital variations of an adaptive 

 tendency, or both, are, as a matter of fact, adapted to their 

 environments ; and we need not be astonished if the 

 disentangling of the factors is a task of no little difficulty. 



But there is one more point of view. Is the hypothesis 

 that the activity is founded on intelligence quite so satis- 

 factory as at first sight it appears ? It must be remembered 

 that the very appropriateness of many instinctive activities, 

 and their adaptation to the needs of the species, lead one 

 to suppose, at first, that they are based on intelligent, 

 nay, even on rational considerations. And yet closer and 

 more searching study shows this view to be untenable. 

 One might well suppose, for example, that the hen 

 undertook the labours of incubation because she knew 

 that the result would be a brood of chicks. But when 

 we come to inquire on what grounds she could possibly 

 reach such a conclusion, it is difficult to give a reply 



