1 91 8. J hy Birds of Eggs unlike their own. 149 



visionary about tliis suggestion, and, in view of my results 

 from the strongly heteroic Warbler, Apalis thoracica, I am 

 mucli interested to note that two eggs of Chrysococcyx 

 klaasi, taken by Messrs. Haagner and Ivy from its nests, 

 resembled in coloration (though not in size) the particuUxr 

 form of the Warbler's egg with which they were found 

 (Journ. S. A. O. U. ii. 1906, p. 36, figured pi. iii.). 



Discrimination comes next, and this, as my experiments 

 seemed clearly to show, has in some birds probably become 

 a most efficient defence, right up to the point at which the 

 coloration of the Cuckoo's egg exactly resembles that of 

 the host's. The carrying away of the egg that apparently 

 took place in most of my experiments was possibly useful, 

 not merely in relation to detection by enemies, but for the 

 baffling of the Cuckoo, should it be in the habit of ever again 

 utilising the egg, though I do not regard this advantage, if 

 it exists, as other than incidental. Spiking, and the evi- 

 dences of destruction of the egg seen in Weavers' nests, 

 would be still more effective, but the former may sometimes 

 be merely a convenient way of carrying a large egg out of 

 the nest. This was obviously not the explanation for the 

 spiking of a Pycnonotus egg by a Fhyllastrephus, described 

 above. 



Whether its fellow-nestlings, once the Cuckoo is hatched, 

 have any further chance of escape, might be the subject of 

 further observation. Especially might those instances be 

 studied in which the young Cuckoo retains nest mates. 

 Some nestlings have, from the outset, far greater grasping- 

 power than others and cannot be lifted without bringing the 

 lining of the nest with them. I found that differences in 

 this respect made a difference to the young Cuckoo I experi- 

 mented on, but' I had no really strongly-marked example 

 to test and the Cuckoo successfully solved all reasonable 

 problems that I set him to work on. Against the possibility 

 that grasping-power might be of use to the host's nestling- 

 may be set Mr. John Craig's fascinating observations which 

 I have recently seen qiioted in Mr. Percival WestelTs book 

 on 'British Bird-Life.' Truly Homeric struggles took place 



