possibly be on the alert. But a herd of
such animals, when considered as a whole, is always on the alert; at
almost every moment some eyes, ears, and noses will command all
approaches, and the start or cry of alarm of a single beast is a
signal to all his companions. To live gregariously is to become a
fibre in a vast sentient web overspreading many acres; it is to
become the possessor of faculties always awake, of eyes that see in
all directions, of ears and nostrils that explore a broad belt of air;
it is also to become the occupier of every bit of vantage ground
whence the approach of a wild beast might be overlooked. The
protective senses of each individual who chooses to live in
companionship are multiplied by a large factor, and he thereby
receives a maximum of security at a minimum cost of restlessness.
When we isolate an animal who has been accustomed to a gregarious
life, we take away his sense of protection, for he feels himself
exposed to danger from every part of the circle around him, except
the one point on which his attention is momentarily fixed; and he
knows that disaster may easily creep up to him from behind.
Consequently his glance is restless and anxious, and is turned in
succession to different quarters; his movements are hurried and
agitated, and he becomes a prey to the extremest terror. There can
be no room for doubt that it is suitable to the well-being of cattle
in a country infested with beasts of prey to live in close
companionship, and being suitable, it follows from the law of
natural selection that the development of gregarious and therefore
of slavish instincts must be favoured in such cattle. It also
follows from the same law that the degree in which those instincts
are developed is on the whole the most conducive to their safety. If
they were more gregarious they would crowd so closely as to
interfere with each other when grazing the scattered pasture of
Damara land; if less gregarious, they would be too widely scattered
to keep a sufficient watch against the wild beasts.

I now proceed to consider more particularly why the range of
deviation from the average is such that we find about one ox out of
fifty to possess sufficient independence of character to serve as a
pretty good fore-ox. Why is it not one in five or one in five hundred?
The reason undoubtedly is that natural selection tends to give but
one leader to each suitably-sized herd, and to repress superabundant
leaders. Ther