66 A YOUNG CUCKOO 



as to the truth of Dr. Baldamus's theory (the only 

 theory, by the way, he has put forth), as to the 

 object of the assimilation being to render the 

 Cuckoo's egg * less easily recognised by the foster- 

 parents as a substituted one.'. 



Submissive to experiment as the Hedge-sparrow 

 may be, she is not alone in this respect. If the 

 Hedge-sparrow will brood the Redbreast's egg, the 

 Redbreast likewise will brood that of the Hedge- 

 sparrow. In fact, tricks of this kind may be played 

 upon almost any bird within similar bounds. 



How comes it, then, that the Cuckoos' eggs laid 

 in the nests of Hedge-sparrows have failed, save in 

 instances so rare as to be accounted phenomenal, to 

 become assimilated to those of that species, whilst 

 the Cuckoos' eggs laid in the nests of Redbreasts 

 show similarity to those of the Redbreast ? 



Before the question can be answered, some 

 confusion as to the nature of assimilation must be 

 cleared away. This is caused by the words in 

 which Professor Newton endorses Dr. Baldamus's 

 theory: "there can hardly be a doubt as to the 

 truth of Dr. Baldamus's theory (the only theory, by 

 the way, he has put forth), as to the object of 

 the assimilation being to render the Cuckoo's egg 

 'less easily recognised by the foster-parents as a 

 substituted one.' ' 



But in what sense can assimilation be said to have 

 an object, unless as a matter of metaphysics ? I 

 understand Natural Selection as applied to the 

 process of assimilation to consist in the following: 

 Certain Cuckoos laid eggs in the nests of other 

 birds. In cases when such Cuckoos' eggs were 



