178 THE ZOOLOGIST. 



duces a much larger variety than in other birds. And if we further apply 

 to the Cuckoo the law of heritage, over and above the difference in food, 

 the variation in the eggs would be enormously increased. Considering the 

 manifold variety thus produced, it is quite possible that the eggs of the 

 Cuckoo should assume a likeness to the eggs of other birds, even of such 

 as it does not choose to lay with. We must also admit that the principle 

 that the food of many birds, though it may not affect their own eggs, has 

 its influence on the colouring of the eggs of their offspring, can also be 

 applied to the Cuckoo, in the case also when it is nurtured for generations 

 in the nests of the same species of birds whose eggs do not vary much. 



We can, with some amount of certainty, assume that our Cuckoo, before 

 he became a nesting parasite, laid monochrome blue eggs, as we see now in 

 its near relatives the North American Coccyzus americanus and C. erythro- 

 phthalmus, which have already occasionally begun to give up rearing their 

 own young. The blue eggs of the Cuckoo, exclusively found in the nests 

 of the Redstart, which also lays blue eggs, may be traced to similarity 

 of food and inheritance. 



