228 OUR SUMMER MIGRANTS. 



be), and the Cuckoo can have no reason for 

 continuing the practice of using the same kind 

 of nest from one season to another. 



While admitting therefore the tendency which 

 certain habits have to become hereditary in cer- 

 tain animals, I feel compelled to reject the appli- 

 cation of this principle in the case of the Cuckoo, 

 on the ground that it can only hold good where 

 the habit results in an advantage to the species, 

 and in the present instance we have no proof 

 either that there is an advantage, or, if there is, 

 that the Cuckoo is sensible of it. 



Touching the question of similarity between 

 eggs laid by the same bird, Professor Newton 

 says : " I am in a position to maintain positively 

 that there is a family likeness between the eggs 

 laid by the same bird " (not a Cuckoo) " even at 

 an interval of many years," and he instances 

 cases of certain Golden Eagles which came 

 under his own observation. But do we not as 

 frequently meet with instances in which eggs 

 laid by the same bird are totally different in 

 appearance ? Take the case of a bird which 

 lays four or five eggs in its own nest before it 



