68 A YOUNG CUCKOO 



Having cleared away this ambiguity, we return to 

 the question why the Cuckoo's egg laid in the nest 

 of the Redbreast approximates at times to that laid 

 by the Redbreast itself, whilst the Cuckoo's egg laid 

 in the Hedge-sparrow's nest does not, setting aside 

 alleged but very rare instances of agreement. 



Regarding the general question of the alleged 

 exercise of discrimination by foster-parents, I would 

 ask Who ever found a Cuckoo's egg ejected from 

 the foster-nest so as even to afford a presumption 

 that it had been discriminated against ? Who ever 

 found a foster-nest containing a Cuckoo's egg 

 deserted ? Yet, assimilation cannot be said to have 

 been so perfected as to make discrimination a thing 

 of the past. 



There being no such evidence of the exercise of 

 discrimination in general, there is no need to inquire 

 why it should have been exercised by the Redbreast 

 and not by the Hedge-sparrow. 



If it be true that assimilation has taken place and 

 to prove that we should require, as already stated, 

 to know what type (or types) of egg was laid by the 

 Cuckoo when first it was foisted upon its neighbours 

 it would naturally most easily be accomplished in the 

 case of foster- species laying eggs most resembling 

 the type of egg originally laid by the Cuckoo. If 

 this was anything like the average of existing tpyes, 

 one can well understand that, given the degree of 

 variability known to exist among the eggs of Cuckoos 

 of various species, frequent cases of apparent 

 assimilation would arise among eggs of a similarly 

 dull, mottled, indeterminate type. It is among such 

 eggs that resemblance is most found. On the other 



