THE COLOURATION OF BIRDS' EGGS. 451 



to me that naturalists when they endeavour to trace in the colours of 

 eggs in nests protective features, have altogether gone astray. It is 

 with some diffidence that I venture to put forward what is in effect a new 

 theory of the colouration of birds' eggs, for I am not a collector of eggs. 

 Nevertheless the -unsatisfactoriness of the theory which at present holds 

 the field emboldens me to put forward my views upon this interesting 

 subject. 



I would divide eggs Into three classes as regards their coloration, — 

 those which are laid in dark places, those which are deposited in the open 

 and not in a neat, and those which are laid in nests, yet exposed to 

 daylight. 



It seems to me that each of these three classes is exposed 

 to an altogether different environment. The birds which build nests 

 In deep holes or caverns must incubate them in almost total darkness. 

 It must be a matter of considerable difficulty for such birds to distin- 

 guish their eggs ; the only possible way for these to be visible is for 

 them to be coloured white. It is, I think, of considerable importance 

 that nesting birds should be able to see their eggs, for they have not 

 the brain power to count them, so that if their eggs were quite 

 invisible, some of them would by accident often get separated from the 

 rest and thus fail to be hatched. Therefore natural selection will tend 

 to cause the eggs which are laid in really dark places to become white. 

 As evidence that it is important that the eggs under such circumstances 

 should be white I may mention the puffin, which apparantly used, like 

 its relatives, the auks, guillemots and razor-bills, to nest in the open. It 

 now nests in burrows and covers the pattern on its eggs with a wash of 

 white, through which the markings on the egg are often visible. 

 This seems to me to furnish conclusive proof that the whiteness of eggs 

 laid in dark places is not due merely to the cessation of the action of 

 natural selection as some naturalists assert. I hold that eggs in burrows, 

 &c, are subject to natural selection which tends to cause them to 

 become white, but that natural selection acts thus only in cases 

 where the nest is so dark that coloured eggs would be practically 

 invisible. 



With regard to the second class of eggs — those laid in the open and 

 not in nests but altogether exposed — it is obviously of the greatest 

 importance that such eggs should be protectively coloured, that they 

 should resemble as much as possible their surroundings. That such 



