Page:The Zoologist, 4th series, vol 3 (1899).djvu/577

Rh argued that birds laying white eggs would become extinct without they had gradually acquired the intelligent or automatic powers of concealment through a process of natural selection. But this is only begging the question. The colour of the egg has not altered under this severe stress, and we can see that many eggs are completely either adapted to their environment, or are so marked and coloured that the birds by choosing a proper environment, or, again, exercising active mimicry, can leave such in practical exposure. "Primarily the eggs of birds must have been white, from the inherent colour of the salts of lime and magnesia of the shell." "As a rule, Sandwich Terns' eggs harmonize closely with their surroundings, and even the experienced field naturalist has to exercise a great deal of care to avoid treading upon a clutch when visiting a breeding station. A friend of mine told me a few years back that he had once visited a colony of these birds on an island where the natural breeding accommodation was so limited that many of them had conveyed patches of pebbles on to the grass, and laid their eggs thereon." Take, for instance, our Nightjar or Goat-sucker. As Mr. Watson has remarked, "this night-flying bird, half-Owl, half-Swallow, rests during the day on bare bits of limestone on the fells. Its mottled plumage exactly corresponds with the grey of the stones, and its eggs, in colour like its plumage, are laid upon the bare ground without the slightest vestige of a nest, and again entirely resemble the stone." Now take another good example from Mr. Wallace. The common Black Coot (Fulica atra) "only breeds in certain localities where a large water-weed (Phragmites arundinacea) abounds. The eggs of the Coot are stained and spotted with black on a yellowish-grey ground, and the dead leaves of the reed are of the same colour, and are stained black by small parasitic fungi of the Uredo family; and these leaves form the bed on which the eggs are laid. The eggs and the leaves agree so closely in colour and markings that it is a difficult thing to distinguish the eggs at any distance. It is to be noted that the Coot never covers up its eggs as its ally, the Moor-hen,