this explanation will not hold good for nests that are made in the
holes of trees, as that of sylvia phaenicurus, or which are oven-
shaped with a narrow entrance, as with sylvia rufa. In these cases
the cuckoo can neither slip in nor look in, and must therefore lay
her egg outside the nest and push it inside with her beak; she can
therefore have no means of perceiving through her senses what the
eggs already in the nest are like. If, then, in spite of all this,
her egg closely resembles the others, this can only have come about
through an unconscious clairvoyance which directs the process that
goes on within the ovary in respect of colour and marking.

An important argument in support of the existence of a clairvoyance
in the instincts of animals is to be found in the series of facts
which testify to the existence of a like clairvoyance, under certain
circumstances, even among human beings, while the self-curative
instincts of children and of pregnant women have been already
mentioned. Here, however, {124} in correspondence with the higher
stage of development which human consciousness has attained, a
stronger echo of the unconscious clairvoyance commonly resounds
within consciousness itself, and this is represented by a more or
less definite presentiment of the consequences that will ensue. It
is also in accord with the greater independence of the human
intellect that this kind of presentiment is not felt exclusively
immediately before the carrying out of an action, but is occasionally
disconnected from the condition that an action has to be performed
immediately, and displays itself simply as an idea independently of
conscious will, provided only that the matter concerning which the
presentiment is felt is one which in a high degree concerns the will
of the person who feels it. In the intervals of an intermittent
fever or of other illness, it not unfrequently happens that sick