COLOUR IN BIRDS’ EGGs. 209 
M. Tarkhanoff. He introduced a small ball of amber into the 
upper part of the ovarium, and obtained later on a quite normal 
egg, with chalaze, albumen, and shell, but with the ball of amber 
in place of a yolk. 
At the breeding season, the females of certain animals are 
well known to be especially impressionable, and we think that 
the effect of the surroundings during the time of the formation 
of the shell, upon the mental or nervous constitution of the 
bird, is a main factor in the production of colour in the eggs. 
Any variations of value are seized on by natural selection, and 
transmitted by the principle of heredity. Individuals at the 
present day are influenced in part by the surroundings, but 
mainly restricted by the tribal habits of generations. We have, 
in fact, sufficient adherence to type for an experienced collector 
to be tolerably sure of the species of bird to which a particular 
egg belongs, but sufficient variation to make him wonder at the 
differences which often exist between eggs of the same clutch. 
As we find in all groups, that some species are more stable and 
less variable than others, so the eggs of some birds are appar- 
ently fixed in colour and pattern, while those of others vary 
within wide limits. 
We will now consider in detail the influence of surroundings, 
and the utility of the effects produced. 
The general tint of the egg is often protective. The colour 
of the ground prominently before the vision of the laying bird, 
is reproduced in various shades in the eggs of the Pheasants 
and Partridges, and in our Mallee hen (Leipoa ocellata) and Mega- 
pode. Inthe rich brown variety of the egg of the domestic fowl, 
we probably see the colour developed in the feral state, now 
usually lost by reversion to the original white, as there is no 
longer advantage to be gained by its retention. 
In addition to the protective ground tint, darker spots and 
markings lend further security. The eggs of the Sandpipers 
and Dotterels cannot be distinguished, even when seen from the 
sands on which they lie, without close concentration of the 
attention. Grouse and Quail, Rails and Night-jars, Plovers and 
Terns, Oyster-catchers and Gulls, all lay on the ground, with or 
without nests, and the eggs exhibit different shades of the soil or 
of the rocks, with an appropriate ornamentation of spots, 
blotches, and smears, 
