258 MENTAL FACULTIES SEC. 



parents and of the nature of their nest. And it is in fact all 

 the more probable that such experience is the principal factor 

 in the case in question, and that it has at last become 

 instinctive by inheritance, because we know that the 

 experience of youth also in ourselves, and in the animals 

 of which we know anything on this point, is retained 

 with extraordinary tenacity. Thus, for example, a single 

 punishment is as a rule sufficient to make a young pointer 

 indifferent to hares. Accordingly, the young cuckoo is 

 influenced, not by the inheritance of the occasional habit of 

 its mother, but by the experiences of its education, and by the 

 deficiencies of its education. The cuckoo can never learn to 

 build nests, and must completely lose the nidificating instinct. 

 But, apart from these considerations, it is a question if the 

 occasional laying of eggs in other birds' nests was really the 

 ultimate cause of the cuckoo's instinct. I deny this, and 

 believe that the original progenitors of our cuckoo when they 

 began to lay their eggs in other nests acted by reflection and 

 with design. We have no certain knowledge that the cuckoo 

 does not at the present day lay its eggs in other birds' nests 

 after conscious reflection. We do not know, therefore, how far 

 this action is due to intelligence. That it is not a perfect 

 instinct is shown by the fact above mentioned, that our 

 cuckoo at times sits on her own eggs and feeds her young ; 

 and it is especially noteworthy that it builds no nest for the 

 purpose. 



This is of course disputed. Brehm ascribes the statement 

 to a confusion of the cuckoo with the goat-sucker, but Darwin 

 himself regards it as satisfactorily proved. But if the fact is 

 considered unproved, the other fact that the American cuckoo 

 sometimes incubates its own eggs, sometimes lays them in 

 other birds' nests, and a priori the assumption that the 

 instinct of our cuckoo has been gradually developed, imply 

 that there was a time when it still occasionallv incubated 



