On the Production of Colour in Birds' Eggs. 53 



we may consider the latest views on the subject to be those 

 enunciated by Mr. H. Seebohm in his lecture at the London 

 Institution, December 20, 188G. I had published in the 

 Melbourne Leader of December 26, 1885, a popular account 

 of the colours of Australian birds' eggs, in which I advanced 

 suggestions which seemed to me to throw light on the 

 subject. After reading the abstract in Nature of the 

 interesting lecture b}^ this high authority, I have thought it 

 worth while to make a more formal scientific record of the 

 ideas broached in the Leader. 



My hypotheses may well be encountered with criticism, 

 but they do serve at least very conveniently to connect a 

 multitude of facts together. The antiquity of the Australian 

 Avi-Fauna, and the preservation of ancient types, render a 

 comprehensive consideration of Australian eggs of the greater 

 value. My suggestions have been founded on studies of large 

 collections, and after a certain amount of experience in the 

 field. Australian eggs yield a rich abundance of facts which 

 are of scientific interest j^e?' se, and which will be of still 

 higher value if we can discern their bearing on biological 

 problems. 



We take it that the natural or orioinal colour of birds' 

 eggs is the pure white of the mineral substance (carbonate of 

 lime) of which they are composed, just as the natural colour 

 of bone is white, and that, too, of the shells of mollusca, &c. 

 All shells are secreted by animal membranes. In the 

 mollusca, an external layer of membrane usually remains free 

 from admixture of mineral matter, as an animal epidermis, 

 which can be peeled off. But this is not the case with birds' 

 eggs ; they possess a membranous lining, generally white, 

 occasionally brownish or bluish, but outside this the animal 

 substance and mineral matter are intimately commingled to 

 the very surface. Colour, if produced, is then, in almost all 

 eggs, ingrained. Often it can be detected incorporated in 

 the inner layers of the shell, as blotches beneath the sur- 

 face. 



Birds' eggs have many foes. Even where man has not 

 appeared upon the scene, a number of systematic nest- 

 robbers exist. Snakes, the great lace-lizard (Hydrosaurus 

 or Varanus varius), which takes such liberties with the 

 settlers' hen roosts, the " native cats " (Dasyurus viverrinus 

 and D. maculatus), perhaps the bush rats, and last, but by no 

 means least, other birds, and especially the crows, are veiy" 

 destructive of our native birds' eggs, and of the young birds 



