their bodies. But, except
at this lowest stage, the protection afforded to the young always
involves some instinctive adaptation of the parent's behaviour. We
may see this even among the fishes, some of which deposit their
eggs in rude nests and watch over them, driving away creatures that
might prey upon them. From this stage onwards protection of
offspring becomes increasingly psychical in character, involves
more profound modification of the parent's behaviour, and a more
prolonged period of more effective guardianship. The highest stage
is reached by those species in which each female produces at a
birth but one or two young, and protects them so efficiently that
most of the young born reach maturity; the maintenance of the
species thus becomes in the main the work of the parental instinct.
In such species the protection and cherishing of the young is the
constant and all-absorbing occupation of the mother, to which she
devotes all her energies, and in the course of which she will at
any time undergo privation, pain, and death. The instinct becomes
more powerful than any other, and can override any other, even fear
itself; for it works directly in the service of the species, while
the other instincts work primarily in the service of the individual
life, for which Nature cares little.... When we follow up the
evolution of this instinct to the highest animal level, we find
among the apes the most remarkable examples of its operation. Thus
in one species the mother is said to carry her young one clasped in
one arm uninterruptedly for several months, never letting go of it
in all her wanderings. This instinct is no less strong in many
human mothers, in whom, of course, it becomes more or less
intellectualized and organized as the most essential constituent of
the sentiment of parental love. Like other species, the human
species is dependent upon this instinct for its continual
existence and welfare. It is true that reason, working in the
service of the egotistic impulses and sentiments, often circumvents
the ends of this instinct and sets up habits which are incompatible
with it. But when that occurs on a large scale in any society, that
society is doomed to rapid decay. But the instinct itself can never
die out save with the disappearance of the hu