MIMICRY. 547 



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 environ- 

 ment, 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 accommoda- 

 tion was so limited that many of them had conveyed patches of 

 pebbles on to the grass, and laid their eggs thereon." f 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, 



* James Newton Baskett, ' Papers presented to World's Congress on 

 Ornithology,' Chicago, p. 95. 



t Richard Kearton, ' With Nature and a Camera,' p. 254. 



p. 136. 



2n2 



