388 Mr, E. C. Stuart Baker on the Evolution of 



supposing that the evolution has begun, for instead of finding 

 that most eggs are of the white, sparsely spotted type most 

 often found in the nests of Cisticola, we find that the 

 maiority are of a pinkish ground-colour densely spotted with 

 red, much like, in fact, the eggs of the bird imposed upon. 



Omitting Cisticola, the next most popular foster-parents 

 are undoubtedly birds of the genus Suya. 



All these birds — S. crinigera, S. atrogularis, S. khasiana, 

 or S. superciliaris — lay very similar eggs, though of many 

 types. The most common forms vary from white, but faintly 

 tinged with pink, to a comparatively deep reddish, with 

 spots, specks, and small blotches of deeper red either disposed 

 in a ring about the larger end or distributed more or less 

 profusely over the whole surface. Here the type of Cuckoo's 

 egg most often obtained is neither the pale form found in 

 the Cisticola s nest nor the deep red-coloured one found in 

 that of Triburu, but an intermediate type which assimilates 

 very well with the most common form of the eggs laid by 

 the fosterer. 



Unfortunately for the Cuckoos the Suyas themselves are 

 very erratic, and sometimes lay eggs which have a bright blue 

 ground; but as only one such egg is laid in every ten or 

 twelve, we should expect, if my theory is correct, to find, as 

 is indeed the case, that evolution has followed the most useful 

 line and that the Cuckoo whose strain is most dominant is 

 the one whose egg agrees with the majority, not the minority, 

 of Suyas' eggs. 



Leaving the Warblers, the next most popular foster-parents 

 are birds of the genus Anthus, represented in the Khasia 

 Hills by A. striolatus on the higher ranges and A. rufulus 

 lower down. Neither of these species is nearly so common 

 as Cisticola cursitans, Suya criniyo^a or S. khasiana, but 

 fully 50 per cent, of the nests of Anthus obtained in the 

 above Hills contain Cuckoos' eggs. Here, strange to say, I 

 can find no signs of adaptation ; and this is the more curious 

 when we remember that in regard to the eggs of the 

 European Cuckoo, it is between Pipits' and Cuckoo's eggs 

 that we often find the closest and most remarkable likeness, 



