Adaptation in Parasitic Cuckoos' Eggs. 395 



and texture, differing only in being much smaller and more 

 glossy. So rare are the exceptions to this rule that I think 

 we may take it as a fact that when the Large Hawk- Cuckoo 

 places her egg in other nests, she only does so by mistake or 

 in an emergency. 



The second type of egg she lays is much like the first in 

 shape and texture, but is generally a good deal bigger and 

 is a bright pale blue-green quite unspotted. The first e^^ 

 o£ this kind found was taken by Colonel Rattray from the 

 nest of a Myiophoneus, but this must have been an unusual 

 nest to select, as no others have since been taken from it. 

 The birds appear, in their western range, to place their eggs 

 in the nests of Trochalopterum Uneatum, 7\ nig ri men turn, T. erij- 

 throcephalum, and Ixops nepalensis, whilst in their more 

 eastern habitat they are deposited in the nests of Garrulax 

 monilige?', G. pectoralis, and Trocludopterum chrysopiemm. 



Here we have exhibited a form of parallel evolution by 

 elimination, the one strain of Cuckoo placing its blue egg 

 in the nests of several species of birds laying similarly 

 coloured eggs, and the other surviving strain laying olive- 

 brown eggs in the nests of a single species which also lays 

 eggs of the same uncommon colour. 



The next genus of parasitic Cuckoo contains two species, 

 Coccystes coromandus and C.jacohinus. 



Coccystes coromandus lays but one type of e^^, a large, very 

 spherical blue egg of a silky texture and very fine grain, 

 which cannot possibly be mistaken for any other kind of 

 Asiatic Cuckoo's egg, except in the case of very abnormally 

 small eggs which might be as small as abnormally large 

 C.jacobinus eggs. The usual fosterer which has to entertain 

 the young Crested Cuckoo is one or other of the Laughing- 

 Thrushes, which lay blue eggs similar to the Cuckooes own 

 egg. The principal among these are Garrulax moniliger, 

 G. pectoralis, Trochalopterum squamatum, Grammatopiila 

 striata, G. austeni, and Trochalopterum chrysopterum. On 

 rare occasions only are they placed in the nests oi Actino dura 

 ianthocincla or Garrulax leucolophus, or similar unsuitable 

 nests. Here the elimination of the unsatisfactorilv coloured 



