422 THE GREBES 



ornaments which distinguish this are probably related to the elabora- 

 tion of the secretions of the sexual glands, as we have already suggested, 

 but their character may well have been controlled by the needs of the 

 environment. In the end it may be decided that the whole coloration, 

 throughout the year, is but the expression of idiosyncrasies of growth 

 which have not come directly under the shears of selection, simply be- 

 cause variation did not tend in the direction of undue conspicuousness. 



And now we must turn to the strictly ornamental part of the 

 plumage, which, as we have already mentioned, is furnished by the 

 paired tufts of elongated feathers known as the " ears," which are 

 erectile and capable of a considerable range of movement, and a frill 

 of feathers, also erectile, surrounding the head like an Elizabethan 

 ruff. The white of the fore-part of the face, contrasting with the bright 

 chesnut and dark brown hues of the ruff, makes this last a most 

 conspicuous ornament during the displays to be described presently. 

 These highly decorative plumes are purely ornamental, being dis- 

 carded at the autumn moult. What factors have produced them ? 

 At present this question is unanswerable. That they are intimately 

 associated with the secretions of the sexual glands seems certain. But 

 the fact that no other grebe is adorned in like fashion seems to point 

 to some idiosyncrasy of growth, some temperamental peculiarity. 

 This much may be gathered from their display during what is known 

 as the "courtship" period. But while we now have a fairly complete 

 account of this, we know little or nothing of what obtains under the 

 same circumstances among other grebes, and until these gaps in our 

 knowledge are filled up, much that is recorded of the present species 

 must remain enigmatical. 



As touching the " courtship," much valuable information has been 

 gathered by Mr. Edmund Selous, but besides his observations I am 

 indebted to some extraordinarily interesting notes by my friend 

 Mr. Leonard Huxley. But as these are in the course of publication, I 

 cannot make full use of the facts he has so generously placed at 

 my disposal. 



