74 Mr. E. C. Stuart Baker on [Ibis, 



which are locally migratory, moving up aud down the coast 

 as food and other conditions exert their influence upon 

 them. Now a certain portion of this breeding-ground 

 consists of a dry red laterite, and over this area a large 

 proportion of the eggs found are red also. Our conclusions 

 are that the red eggs are laid by the resident birds and the 

 others by the visitors. It would seem that through the 

 countless generations of Plover which have habitually bred 

 on this red soil, a certain number in each generation have 

 laid eggs more inclined to be erythristic than the others, 

 and such eggs assimilating with the ground better than the 

 ordinarily coloured ones have escaped destruction by vermin 

 in greater degree than the latter. In each generation the 

 erythrism has been emphasized by selection until the present 

 wonderful stage of adaptation has been reached. That it 

 is not casual erythrism is shown by the fact that in one 

 breeding-season Mr. Stuart and his collectors found — I do 

 not say took — over seventy of these wonderful eggs. 



Even admitting this reason for the evolution of the red 

 Sarciophorus egg, we are still only in the first stage of 

 investigation and suggestion, for we have also found that 

 the Red-wattled Lapwing, Sarcogrammus indicus, which 

 breeds freely on the same ground^ has made no advance in 

 the evolution of a red egg. Why should this be? 



The other two groups of eggs shown are similar types 

 of evolution, though in their cases the immediate need fur 

 erythrism has been different. They are both Cuckoos' eggs 

 in which erythrism has been evolved, not for their protec- 

 tion against destruction by vermin, but for the purpose of 

 deceiving certain selected fosterers into undertaking their 

 incubation. 



The central set of eggs belong to the small Indian Cuckoo, 

 Cuculus intermedius, and by this bird we find that two, and 

 only two, very strongly contrasting types of egg are laid — 

 the one pure white, and the other some shade of terra-cotta 

 or chocolate. It is interesting to observe that, though some 

 150 eggs of this little Cuckoo have passed through my 



