48 Life History of Common Cuckoo. 



such procedure likely to be advantageous to the 

 species ! 



The evidence is, however, by no means satisfactory 

 or conclusive that, when two cuckoos' eggs are 

 dropped into one nest the two cuckoos invariably try 

 to turn each other out — the strongest finally prevail- 

 ing. We have just cited two cases where this was 

 not the fact, and others might have been added. 



Yet, Mr. Romanes, with the unfortunate tendency 

 to generalise from too narrow a basis of particulars, 

 writes thus : 



" Among birds we find mistaken instinct exhibited 

 by the cuckoo when it lays two eggs in the same nest, 

 with the inevitable result that one of the young birds 

 will fifterwards eject the other." * 



And in not a few of the cases it is plain that there 

 was no mistaken instinct at all in the sense Mr. 

 Romanes means, because in not a few nests it would 

 be simply impossible to see the former deposited 

 cuckoo's egg : unless Mr. Romanes indeed supposed 

 that these second eggs are invariably deposited by 

 the same bird that laid the first egg — a thing about 

 which we are still in the greatest uncertainty, and 

 certainty regarding which would clear up a lot of 

 other things for us. Meantime Mr. Romanes's words 

 above are only like too many of his — a doubtful point 

 assumed as certain and absolutely settled, and then 

 a bold, big argument, dogmatically raised upon it ! 



In cases where cuckoos' eggs have been deposited 

 in blackbirds' or pigeons' nests there would be a more 

 equally matched contest between the young ones of 

 the different parents from their size ; but in some 



* Romanes's Ment. Evolution, p. 168. 



