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



in full conformity with the view that the display in court- 

 ship is essentially an exhibition of specific and sexual 

 efficiency. 



Four years ago, I held the above view of sexual selection, 

 but I did not regard it as likely, by itself, to make appreciable 

 headway against the powerful factors that make for dullness, 

 and I felt that bright colours and ornamentation could, 

 perhaps, be sufficiently accounted for without it. But my 

 later work, seeming for certain cases to eliminate alternative 

 explanations and revealing unsuspected counteragents, con- 

 vinced me that the selection of the beau-ideal may, under 

 certain circumstances (as in the case of polygamy), have 

 produced great results. I am unable, without it, to account 

 to my satisfaction for the breeding-plumage of male Pyro- 

 melana and Coliuspasser among the birds best known to me 

 in the field, and, as well as the reserve of males, a good con- 

 tingent present here is in the habit of slipping down under 

 the herbage when threatened. 



I have gone into the question a little fully, on account 

 of the striking use of the mouth-colours in courtship and 

 also because we have, in the usually-closed mouth of a bird, 

 so excellent a counteragent for brilliance within it that 

 sexual selection might be expected to have here found a 

 field for its accentuative operations. My adult mouths, since 

 I took up mouth-coloration, have been mostly dry-season. 

 Breeding-season mouths may or may not repay a special 

 study. 



Note. — Since writing the above I have come across several 

 unusually reversionary tongues of nestling Warblers and 

 Pycnonotus — the latter entirely instead of submarginally 

 dusky as figured for this species and for Macroni/x. These 

 rather strongly suggest a derivation of the three-spot and 

 twin-spot tongues from a generally dusky tongue. I figure 

 three of such tongues among the Warblers (text-figure 6). 

 The order is, of course, different from that suggested by 

 the incomplete Dryoscopus series described above. 



