PKOTECTIVE RESEMBLANCES IN VERTEBRATA 63 



nest in the dark still retain traces of patterns which 

 are well developed upon the eggs of their nearest allies 

 with other habits. Thus the egg of the puffin, which 

 nests in a burrow, would be called white at a little 

 distance, but closer examination reveals the presence 

 of very faint spots, which are distributed as in the 

 very distinctly marked egg of the razor-bill.^ Certain 

 other species still lay strongly marked eggs in the 

 dark, and in their case the change of habit presumably 

 took place at a comparatively recent date. Such a 

 conclusion can be tested by an investigation of the 

 habits of closely allied species. Although white must 

 have been the ancestral colour of birds' eggs, it has 

 probably been re-acquired in species which nest in the 

 dark. It would be very difficult to believe that such 

 a habit has persisted continuously since the time when 

 all birds' eggs were white. 



The strongest confirmation of this explanation of 

 the whiteness of hidden eggs is, however, to be found 

 in the colours of the eggs in the various breeds 

 of domestic fowls. If the gradual disappearance of 

 colour is due to the cessation of natural selection, we 

 must expect it to occur, however the cessation has 

 been brought about. Natural selection cannot operate 

 to preserve the colour of eggs laid in the dark, and it 



' This interesting example attracted my attention while looking 

 over a collection of eggs in the possession of my friend, Mr. E. H. 

 Greenly. Mr. H. Seebohm informs me that he has no doubt about 

 the validity of this interpretation, which was suggested in hiu work 

 on British Birds, 1885, vol. iii. p. 367. 



