in conscious intelligence are of one and the same kind, whether among
the lower animals or with mankind--that is to say, that they are
acquired by apprenticeship or instruction and perfected by practice;
so that the saying, "Age brings wisdom," holds good with the brutes
as much as with ourselves. Instinctive actions, on the contrary,
have a special and distinct character, in that they are performed
with no less proficiency by animals that have been reared in solitude
than by those that have been instructed by their parents, the first
essays of a hitherto unpractised animal being as successful as its
later ones. There is a difference in principle here which cannot be
mistaken. Again, we know by experience that the feebler and more
limited an intelligence is, the more slowly do ideas act upon it,
that is to say, the slower and more laborious is its conscious
thought. So long as instinct does not come into play, this holds
good both in the case of men of different powers of comprehension and
with animals; but with instinct all is changed, for it is the
speciality of instinct never to hesitate or loiter, but to take
action instantly upon perceiving that the stimulating motive has made
its appearance. This rapidity in arriving at a resolution is common
to the instinctive actions both of the highest and the lowest
animals, and indicates an essential difference between instinct and
conscious deliberation.

Finally, as regards perfection of the power of execution, a glance
will suffice to show the disproportion that exists between this and
the grade of intellectual activity on which an animal may be
standing. Take, for instance, the caterpillar of the emperor moth
(Saturnia pavonia minor). It eats the leaves of the bush upon which
it was born; at the utmost has just enough sense to get on to the
lower sides of the leaves if it begins to rain, and from time to time