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



Quite possibly, in such cases as the Grebe and Coot, the 

 conspicuous feature is often useful, as Mr. Pycraft suggests, 

 as " a recognition mark, enabling the parents to find the 

 young after they have dispersed into hiding to avoid an 

 enemy " ; but I cannot help suspecting that all these cases 

 Avill probably be found to resemble the Centropus in the 

 possession of some degree of nauseousness, aud that the 

 main factor in the selection of the distinctive features — or 

 in their retention in the nestlings if they were originally 

 selected in adult ancestors — will have been the need for 

 differentiation by enemies from pleasanter geographically- 

 associated species and a pleasanter parent-form, conformity 

 with that necessity being brought about by mistaken attack 

 and unmistaken refusal. On this view there is far less 

 difficulty in accounting for ornamentation, not only in 

 nestlings but throughout the animal kingdom, including 

 those cases in which the possession of a conspicuous dis- 

 tinctive feature constitutes a departure from the rule of the 

 genus or family, and for that other class of case, often 

 quoted, in which two animals, be they adults, young, or 

 eggs, are found exposed to the same environment and the 

 same enemies and possessing similar habits : yet one is 

 conspicuous, the other concealed. 



Distinctiveness of a less marked order is less uncommon 

 and, in naked nestlings, depends much on skin-colour. I 

 have thought that blackness might be for protection from 

 the sun. That this is not the only factor, if it be one at all, 

 is shown by the fact that, at any rate in Africa, some of the 

 blackest as well as of the least pigmented nestlings are found 

 in covered nests. Both are also found in open nests. The 

 influence of enemies will have to be invoked, I believe, to 

 help us to, at any rate, a complete understanding of nestling 

 appearance, and, incidentally, of some of the resemblances 

 between unrelated nestlings. Those between Hawks and 

 Owls and those between the members of some naked colouz'- 

 groups are quite likely neither in their origin nor in their 

 use entirely a matter of mimicry ; yet the resemblances are 



