284 Mr. C. F. M. Swynnerton on the 



quite independently — demonstrably so — that suggestions 

 of mimicry should be made with caution and reserve. 

 Again, someone may some day demonstrate that Chloropeta 

 is itself a Warbler ! In that case, too, I will gladly withdraw 

 my suggestion. 



Or — as I have already practically suggested, and as is 

 exceedingly likely — fuller records may show that the twin- 

 spot tongue is to the mouths of nestlings what the longi- 

 tudinally-striped pattern is to the down-plumages of young 

 birds — an ancestral character of extremely early date, 

 surviving in a number of now unrelated descendants 

 through the advantages it still continues to offer those 

 jDarticular species or groups of species ; not in this case 

 advantages of concealment, but of easy memorability. I 

 am finding the twin spots, since I first wrote this paper, in 

 more and more birds — Zosterops, Erithacus, Laniarius, &c. 



Yet another case of homoeochromatism is found at 

 Chirinda in the nestling-raouths of Pycnonotus layardi, 

 Hyphantornis jamesoni, and a Chrysococcyx, probably C. 

 cupreus^ found in the latter's nest (figs. 13-15). Not 

 looking at it carefully, I took it for granted that the 

 young Cuckoo was a Weaver, and continued to do so 

 until after opening its mouth and settling down to draw 

 it. Then I noticed the palate and, looking, found the 

 raised nostrils. C. cupreus lays much, I believe, in nests of 

 Hyphantornis. Whether its other hosts are as well chosen 

 in the matter of mouth-colour I do not know. Should this 

 prove not to be a mere isolated coincidence, the question 

 might arise whether it might have come about by the dis- 

 criminative action of enemies or of the parent bird. The 

 latter seems to me more likely to come into play in eggs 

 than in relation to the hatched bird *. The presence of the 



* Since writing this T have placed a young Sitagra ocularia in the 

 nests of a Rock-Thrush {Monticola angolensis) and a Flycatcher 

 {Chloropeta natalensis). It was adopted in each case, in spite of its 

 different external appearance, its very different mouth, its extraordinary 

 manner, and its different call-note. The Rock-Thrush had ejected eggs 

 not its own — a most interesting and significant fact which I will 

 acknowledge more fully later. 



