Adaptation in Parasitic Cuckoos' Eggs. 397 



and I have eggs from the nests of ^-E. seherice, ^E. gouhli(B, 

 and ^E. saturata, in regard to which adaptation may be 

 considered complete. 



The only other Indian parasitic Cuckoo which it is necessary 

 to mention is the Koel, Eudynamis honorata, which lays its 

 eggs in the nest of the Indian Crow, Corvus splendens, its 

 Burmese cousin, C. insolens, or in that of the Jungle-Crow, 

 Corvus macrorhynchus. In addition to these I have also 

 records of its eggs having been found in the nest of 

 Pica sericea in Burmah. The Koel's eggs agree very well 

 with those of all these fosterers, and it is also noticeable 

 that its eggs are not small for the size of the bird ; diminu- 

 tion in size is not necessary, as the Crows' eggs are bigger 

 than its own. 



The foregoing notes will possibly suffice to show that from 

 the numerous and varying types of eggs laid by parasitic 

 Cuckoos those eggs Avhich contrast most vividly with the 

 eggs of the foster-parents are being gradually eliminated. 

 In some genera and species, such as Coccijstes, which we 

 may therefore presume to be one of the oldest forms of 

 Cuckoo, this process of elimination has been going on for so 

 long that the Cuckoos who originally laid ill-adapted eggs 

 have died out, whilst those which laid eggs closest in 

 appearance to the fosterers have survived, succeeding gene- 

 rations of the latter having finally eliminated all abnormal 

 strains until almost perfect adajjtation has been secured. 

 Especially in the remarkable adaptation of the egg of 

 Cacomantis merulinus to suit the bright red egg of a 

 special foster-parent within a small range of country, we 

 have a case which the opponents of evolution in adaptation 

 will find very hard to get over. 



Before concluding I should perhaps say something in 

 answer to the non-evolutionary theorists, who assert that the 

 whole of the contention that foster-parents do sometimes 

 refuse to incubate Cuckoos' eggs is onlj' an illusion. 

 That some birds do so refuse would, however, seem to be 

 partly proved to be true by the fact that I have sometimes 

 found nests, containing a Cuckoo's egg, deserted by the 



