206 jMajor R. F. Meiklejolin oyi the [Ibis, 



tliese species : yet^ in comparison with other birds, their 

 nests are rarely used. 



Boraston, however, comments on this — -that, if so, it was 

 by a more rigorous application of natural selection ; that 

 is, by refusing to luitch any Cuckooes e^^ that did not 

 closely reseml)le their own, these four species eliminated all 

 would-be patrons excej)t those laying eggs so like their own 

 as to escape detection, and that, in consequence, only these 

 four strains were preserved. He then adds that such a 

 theory will hardly bear examination. 



If, then, we reject the conclusions of Key and Wasman, 

 the question arises as to what theory we can substitute 

 Avhich will fit our facts. We are, I think, forced to admit 

 that the resemblance in the colour of Cuckoos' eggs to the 

 types of those of the foster-parents selected is not merely 

 accidental, arising from the great differences in coloration, 

 but that there is some fundamental law which Nature 

 lias ordained to give them tha advantage of protective 

 coloration. 



It has always seemed strange to me that all the autho- 

 rities, so far as I know, have accepted the idea that the nest 

 is selected before the egg is laid, but this is probably due to 

 the fact that eggs of the foster-parents are occasionally 

 removed the day before the Cuckoo deposits its e^g in the 

 nest. Yet, as Dr. Rey points out, it does not necessarily 

 follow that the Cuckoo deposits its egg in another nest 

 on the day on rvhich it is laid, though had the nest been 

 already decided on there seems no reason why this should 

 not be done. 



I personally think that the main point in the problem is 

 whether the Cuckoo selects a nest because the eggs in it 

 resemble her own, or whether the fact of one particular 

 species being selected for several generations has any efl'ect 

 on the egg- coloration, and I consider the former is far 

 more likely to be correct. The latter assumption, as has 

 been pointed out, presents many difficulties, whereas the 

 former would appear to solve them. 



This idea was, indeed, first started by Baldamus, and 



