opening the cocoons in which their larvae are confined and for
setting them free, the larva being unable to do this for itself. Yet
the life of only a few kinds of insects lasts longer than a single
breeding season. What then can they know about the contents of their
eggs and the fittest place for their development? What can they know
about the kind of food the larva will want when it leaves the egg--a
food so different from their own? What, again, can they know about
the quantity of food that will be necessary? How much of all this at
least can they know consciously? Yet their actions, the pains they
take, and the importance they evidently attach to these matters,
prove that they have a foreknowledge of the future: this knowledge
therefore can only be an unconscious clairvoyance. For clairvoyance
it must certainly be that inspires the will of an animal to open
cells and cocoons at the very moment that the larva is either ready
for more food or fit for leaving the cocoon. The eggs of the cuckoo
do not take only from two to three days to mature in her ovaries, as
those of most birds do, but require from eleven to twelve; the
cuckoo, therefore, cannot sit upon her own eggs, for her first egg
would be spoiled before the last was laid. She therefore lays in
other birds' nests--of course laying each egg in a different nest.
But in order that the birds may not perceive her egg to be a stranger
and turn it out of the nest, not only does she lay an egg much
smaller than might be expected from a bird of her size (for she only
finds her opportunity among small birds), but, as already said, she
imitates the other eggs in the nest she has selected with surprising
accuracy in respect both of colour and marking. As the cuckoo
chooses the nest some days beforehand, it may be thought, if the nest
is an open one, that the cuckoo looks upon the colour of the eggs
within it while her own is in process of maturing inside her, and
that it is thus her egg comes to assume the colour of the others; but