132 Mr. C. F. M. Swynnerton on Rejections [Ibis, 



eggs taken from the nest were unluekily destroyed by a 

 cat when I had brought them in to blow. It was a dis- 

 appointment, as I had hoped to exhibit all, feeling that 

 no one conld see them together and deny that selection 

 by foster-parents might have brought about the very closest 

 resemblances that exist between any Cuckoo's eggs and its 

 host's. I hope later to figure the others ^. 



6. The ability to distinguish did not depend entirely on 

 the presence of the host's own eggs for comparison, though 

 their presence ivas undoubtedly helpful. — When two of the 

 eggs of a Rock-Thrush [Monticola angolensis) hatched, a 

 third with which I had been experimenting failed to hatch, 

 I had no other blue eggs in hand, so painted a white egg of 

 Hyphantornisjamesonigreems.]i-h\ne and substituted it for the 

 Rock-Tlirush's egg. It was adopted. A few days later I took 

 it out and put in a Layard Bulbul's egg. It was rejected. 

 I then returned the painted egg, and it was adopted. 

 Two daj's later I painted it with a number of light brown- 

 madder blotches, and it was rejected." Actually the Weaver's 

 egg was painted of a slightly deeper shade than the Rock- 

 Thrush's and, I fear, rather smearily. It also differed 

 from it in its elongated shape and somewhat smaller size, 

 and it is perhaps doubtful if it would have been accepted 

 had the host's egg been there for comparison. But ivider 

 departures were at once rejected. A Bulbul (P. layardi), 

 that had discriminated very finely, nevertheless accepted 

 two eggs of another form (of her own species) on my 

 finally removing her own two eggs ; so that it may actually 

 be that a Cuckoo's best chance would lie in* finding a nest 

 with only one egg. 



7. Evidence jor the view that polymorphism in the host's 

 eggs may be of use against Cuckoos. — I watched a Bar- 



* On p. 568 of ' The Ibis ' for October 191 G, I spoke of Pycnonotus 

 Inyardi as laying very variable eggs, but did not include it in the 

 heteroic category. This was hardly correct, for its eggs may be 

 divided into feveral distinct forms, even though they are close enough 

 to each other and sufficiently connected in some cases by ti'ansition to 

 give the superficial appearance of general variability. 



