562 Mr. C. F. M. Swynnorton on 



them with its wings, and it may be that it was in some 

 simple action like this that, as I liave suggested, the whole 

 instinct and action of ejection originated. I will discuss the 

 experiments more fully in a more appropriate place. 



Are Tongue-spots a Nestling Adaptation ? — I secured two 

 nestlings of Dryoscopus guttatus, so fully fledged that the 

 male flew from the nest on my approach and was only 

 captured with a little difficulty. They still had the perfectly 

 plain orange-yellow mouth. Nearly three weeks later, 

 when they were well able to fly, they were commencing to 

 show the twin spots, and a fortnight later those of the male 

 were very pronounced, the mouths being otherwise still 

 orange-yellow. A fortnight or so later, the female was 

 at the stage then reached by the male, with a mouth 

 equivalent to the nestling mouth of, say. Prima mystacea 

 or Laniarius suJphureipectus. The male had advanced 

 further, through a stage which one often finds represented 

 in nestlings of Cisticola natalensis — tongue and inside of 

 mouth flesh-coloured, submarginal parts still yellow — 

 through an all-pink stage (with twin spots) that occurs in 

 other nestlings of the same Cisticola, as well as in other 

 warblers, and that, without the twin spots, would be like 

 the adult mouth of Lanius collaris, to a stage in which an 

 incipient darkening of the apical portions of the mandibles 

 produces a resemblance to the mouth of several adult birds — 

 Batis molitor and B. erythrophthalma, Graucalus pectoralis 

 and ccesius, Podiceps capensis, etc. The final stage, as we 

 know, will be all black. 



Of course it may be argued that if the twin spots were 

 the last dark colour to disappear, they may be the first to 

 appear again with the re-darkening of the mouth, and that, 

 though a nestling adaptation, they have had in this instance 

 to give way for a time to a pattern which, under the species^ 

 present circumstances, offers it greater advantages — perhaps 

 enabling the young to be mentally associated by enemies 

 with those of Lanius collaris, which the female Dryoscopus 

 nestling rather strongly resembled. Much further work is 

 needed, including observation of embryonic tongues within 



