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



contributed to the selection of special markings or a pale- 

 flanged dark mouth in other cases as well. But as a com- 

 plete explanation for the whole of the striking phenomena 

 of the coloration of nestlings' mouths the explanation is 

 inadequate, and I am inclined to agree with all that 

 Mr. Ingram says on the subject (* Ibis/ 1907, p. 576). 



Thus, the mouth of a Starling (Lamprocolius splendidus), 

 which nests in a hole, is described by Mr. Bates (* Ibis,' 

 1911, p. 542) as follows: — "Flesh-coloured tinged with 

 yellow '* with " conspicuous white mouth-flange " and a 

 dark tongue " becoming black at the base." This strikes 

 one as, perhaps, a very perfect instance of what, with 

 variations, we might naturally expect throughout if the 

 "directive marking" view be universally applicable, even 

 the excellent device of luminous points on the outer 

 margin, as described for Poephlla, being hardly an improve- 

 ment on such a mouth. Yet in the English Starling, which 

 also builds in a hole, the mouth remains plain bright yellow, 

 like that of the Mistle-Thrush (fig. 26), the Fiskal Shrike 

 (figs. 16, 47), and a number of other nestlings whose parents 

 lay in open, brilliantly-lit nests. In this case, at any rate, the 

 plainness would appear not to have been of such great detri- 

 ment as to necessitate the selection of an additional signal 

 for use in holes. And even these plainly pigmented mouths, 

 whether in holes or out of them, require some explanation. 



Again, if we admit that in the Warblers which build domed 

 nests, the twin spots at the base of the tongue have been so 

 vitally useful " directively " as to have been selected for that 

 reason aloue, while Sylvia, taking again to open nests, has 

 begun to have the spots obscured ; and if we argue similarly 

 for the white spots of the Bearded Tit (some of the most con- 

 spicuous of which, like the third spot of Locnstella, seem to 

 me to be frankly me^-directive) . Why, then, is it that Alauda 

 (fig. 30), nesting openly on the ground, has adopted the same 

 spots as the Warblers — with the addition, it is true, of three 

 spots as widely misdirective as the length of the tongue and 

 the mandibles will allow ? Why has Macronyx (figs. 19, 20), 

 nesting openly on the ground, developed the same markings 

 as the Bearded Tit? Is there any really good reason to 



