COLOUR IN BIRDS’ EGGS. 213 
trees, where, of course, the colour cannot be protective, yet the 
eggs retain the family peculiarity. Here we see natural selection 
apparently ruled out of court, and mental receptivity as the sole 
cause of the variations in the one specified direction. The eggs 
of the other members of the family are, from their situation, 
inaccessible, and it therefore seems very questionable whether 
the factor of natural selection has operated at all in the case of 
the eggs of this group. We find very different degrees of develop- 
ment of the blotches. In one clutch of the Sparrow Hawk 
(Accipiter torquatus) one egg was white, a second smudged, and 
the third well blotched. In a clutch of the Goshawk (Astur 
approximans), again, one egg was smudged, one smudged and 
blotched, and the other blotched. Similar gradations are to be 
observed in the average colour of the species. The eggs of the 
Harriers (Circus), which lay on or near the ground, and 
generally among thick scrub, and those of the Crested Hawk 
(Baza subcristata), which builds in the holes of trees, are pure 
white ; and we have gradually more and more colour introduced, 
until the climax is reached by the Brown Hawks (Teracidea 
berigora) and Kestrels (Tinnunculus cenchrovdes ). 
Great irregularity, and much variation amongst individuals, 
characterise eggs which derive their colour from changing and 
varying appearances. We obtain thus a natural explanation of 
the infinite variety of colouring in the eggs of the rapacious 
birds, and of such birds as the Magpies and the Sparrows. 
Many birds continue to protect their eggs themselves, con- 
sciously or unconsciously. Some, as the Partridge, will cover 
up the eggs when they leave the nest. The Grebes lay eggs 
which are at first white, but become stained by mud from the 
body of the sitting mother bird, usually brown, and gradually 
browner, a tint well in keeping with the colour of the nest of 
dead reeds and leaves. Many of the sea birds, too, by fouling 
their eggs, no doubt materially assist in preserving them. 
The English Cuckoo commonly chooses the nests of Larks 
or of Wagtails for its egg. When found in the nest of a Lark, 
especially of a Tit-lark, the egg is very dark; and when found 
in that of a Wagtail, much lighter. This looks like proof 
positive of the effect of mental impression in producing the 
colour of the egg. More rarely, the egg of the Cuckoo is found 
in other nests, such as that of the Hedge Sparrow. It is most 
