i 4 o SPRING 



puffin sits on a single white egg, clouded with a few faint 

 greenish stains. This atrophied marking is very interesting, 

 as it suggests that the puffin's burrowing habits are com- 

 paratively recently acquired, and that it formerly laid its 

 eggs in the open, like the razorbill and guillemots. The 

 eggs approximate to the plain whiteness which is usual 

 with eggs laid in holes, but have not yet quite lost their 

 outdoor markings. Petrels and shearwaters, which nest 

 in similar subterranean holes and crevices, lay pure white 

 eggs, and only one apiece. Cormorants and gannets also 

 lay white eggs, but build a bulky nest of seaweed, sticks, 

 or various seaside plants ; and in this case the white eggs 

 seem to represent the primaeval colour of those of the 

 lizard-like ancestors of the race. It seems probable that 

 all birds' eggs were white to begin with, like those of 

 crocodiles and snakes ; and cormorants', gannets', and grebes' 

 eggs have never got beyond this stage. All are covered 

 with a rough calcareous wash, beneath which the inner 

 shell is pale green. But this greenish hue is less a 

 definite colour than the absence of one ; many birds — 

 for example, chaffinches and nightingales — lay malformed 

 or infertile eggs with pale bluish or greenish shells, and 

 this seems merely to represent an imperfect stage of 

 development. Gannets lay only one egg, common cormo- 

 rants two or three, and shags three or four. Three is 

 also the usual number laid by gulls, though two in a set 

 are not infrequent, and four are now and then laid by the 

 smaller kinds. 



There is a general tint of olive-green or light brown, or 

 1 stone colour,' running through the ground of gulls' and terns' 

 eggs, which clearly distinguishes them from those of other 

 sea-birds. On the other hand, they are often very hard to 

 distinguish from each other, except by size. When the eggs 



