286 MR. E. C. STUART BAKER ON 



Turning now to instances of evolution which are incomplete 

 but which show considerable advance, there can be no better 

 example than that of the little Cuckoo, Caccomantis passerinus. 

 This Cuckoo is found in different geographical races from Ceylon, 

 through practically the whole of the Indian Empire. In many 

 portions of its area we do not yet know what are its normal 

 fosterers or we have not yet sufficient evidence to show to what 

 degree evolution has progressed. We may say, however, that 

 over most of its range it lays principally in the nests of Oisticola, 

 Orthotomics and Franklinia ; in the Nilgiris and adjoining hills 

 it breeds freely, making use of the nest of Prinia inornata ; in 

 Assam and the North-East, where it is possibly more common 

 than anywhere else, the fosterers selected are of the genera Suya 

 and Gisticola ; whilst in Hyderabad (Deccan) Prinia socialis seems 

 to form the sole fosterer. 



Has anything been evolved towards perfecting the resemblance 

 of the eggs of Caccomantis to those of its many fosterei-s ? The 

 answer is " Tes, much " ; and if Ave take them seriatim as given 

 above, we shall find that this is so. 



Roughly speaking, the eggs of Cisticola, Orthotomus and 

 Franklinia are either white or pale blue in ground-colour and 

 are speckled with dark brown in the first-named ; blotched, 

 spotted, or speckled with various shades of red or brown in the 

 second and third. Orthotomus is the most common of the three 

 genera and also the most universally distributed and with the 

 longest breeding-season. Caccomantis over all this area lays an 

 Qg^ YQi-j like that of Orthotomus and not strikingly unlike that 

 of the two other genera. The ground-colour varies from white 

 to blue just as it does in the fosterer's eggs but the blotches are 

 generally larger, paler and more smudgy in character than in 

 any of the other eggs except those of Orthotomibs and they are 

 also decidedly larger. 



In the Nilgiris the Cuckoos' eggs seem always to be pale blue 

 with blotches of reddish, whilst those of its local fosterer, Prinia 

 inornata, are blue with dark, bold blotches of reddish black or 

 blood -red. 



In Assam the fosterers selected, Suya and Gisticola, lay, 

 the former, eggs which are white to rather deep blue-green, 

 marked in many ways with specks, spots, and small blotches of 

 reddish to blackish br-own, the latter, white or very pale blue 

 eggs speckled with brown. Of the two fosterers, birds of the 

 genus Sioya are the more popular, both khasiana and crinigera 

 being impartially cuckolded. 



Many of the Cuckoos' eggs agree fairly well with the eggs of 

 Cisticola but many cannot, unless one tests the shell and weighs 

 the egg, be distinguished from those of the other foster-parents 

 of the genus Suya. I have seen as many as fifty eggs of these 

 birds in one season in the Khasia Hills, but I am quite sure 

 that many of these would have escaped my notice had I not been 

 always on the look-out for Cuckoos' eggs and naturally suspicious 



