LECTURES. 29 
the hen sits very close and only leaves the nest after dark. Again, 
chalky white eggs are often laid on nests made of seaweed, and the 
decaying nest material itself stains them. One case I might mention 
where the parent seems to make a special arrangement for the safety 
of the eggs and where the colouring cannot therefore be said to be 
protective. This is the dabchick, who, when she leaves her nest, 
pulls some of the nest material over the eggs. But, perhaps the 
most interesting case of protective colouring is that of the cuckoo, 
who lays her eggs on the ground, afterwards depositing them in the 
nest of some other bird. The nest may be that of a hedge-sparrow, 
a meadow pipit, a wagtail, or a robin. Now often, though not 
always, the eggs are similar to those of the foster-parent. How can 
such a modification as this take place. In the first place, we must 
imagine that such cuckoo’s eggs as were at all like those of the 
foster-parent ran the best chance of being undisturbed and that any 
egg varying in this direction would be hatched. When the young 
bird, supposing it to be a hen, has grown up and is looking round for 
a nest for her own egg, what can be more likely than that she should 
look upon a nest similar to the one in which she was herself brought 
up as the most desirable. If she had been brought up in a hedge- 
sparrow’s nest she would deposit her egg, which would be the same 
colour as the egg she was herself hatched from, in a hedge-sparrow’s 
nest. 
While on the subject of eggs let me say a few words of their 
form and size. Birds which have conical eggs, as the lapwing, 
generally lay four, and they lie in the nest with their pointed ends 
towards the centre. This seems a convenient form for packing when 
there are several eggs. If the eggs are very round, as those of the 
wood-owl, there are not more than two. 
I think the egg which I hold in my hand is the most interesting 
_form that I know. It is the egg of the guillemot, and 1s, as you see, 
very pointed. The guillemot only lays one egg, and that one she © 
lays on ledges of cliffs, and when she is sitting on her egg she holds 
it tightly pressed to her body. When she rises from the egg a very — 
slight kick would be sufficient if it was round to send it over the edge, 
but being pointed you see it simply describes a circle about its point 
and remains on the ledge. 
If the eggs of birds are large in proportion to the size of the — 
parent bird, and the young have had plently of room to develop they 
are precocious, that is to say, they are able to run about and get © 
food for themselves at once, but birds who for the first few days or ~ 
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