COLOUR OF EGGS. 129 



very little different from those of the wren or the hay- 

 bird (Sylvia Trochilus), which build covered nests 

 with a small side entrance ; while the house-sparrow 

 (Passer domesticus, RAY) lays eggs of dull greenish 

 or bluish-white, streaked with greyish-black, and 

 always builds in holes or under cover. 



As these objections appear to be unanswerable, it 

 will not be necessary for us to follow Dr. Darwin 

 into his fanciful account of the origin of the colours 

 of eggs, which he ascribes to the colour of the objects 

 amongst which the mother-bird chiefly lives, acting 

 upon the shell through the medium of the eye ; for 

 if this were correct, we should have the green-finch 

 and the red-breast, instead of their white eggs, laying 

 blue ones, like the red-start. 



In the case of the eggs of insects, the colours are 

 sometimes, though not in every instance, occasioned 

 by the colours of the embryo shining through the 

 shell, an example of which we have in the small rhi- 

 noceros beetle (Oryctes jiasicornis, ILLIGER*). In 

 birds, however, this never occurs ; and the markings 

 on the eggs seem, so far as we can perceive, to have 

 no connection with the colours and shadings on the 

 feathers. Birds, indeed, of the most varied plumage, 

 such as the peacock and the humming-bird, are 

 produced from white eggs. It is reasonable to con- 

 clude, however, that these colours and markings on 

 eggs are intended to serve some particular purpose, 

 though we may not, in the present state of our 

 knowledge, be able with certainty to say what. 



Without advancing any theory as to the cause of 

 the phenomenon, Mr. Griffiths has deduced some 

 general inferences from the facts in a more cautious 

 way than Darwin and Gloger. *' The eggs,'* he 

 remarks, " of diurnal birds of prey are of a whitish 

 colour, spotted with red, or red spotted with brown. 

 * Insect Transformations, p, 36. 



