offspring as
completely as the capacity of the stomach to digest food is
transmitted. In all animals the new-born stomach needs but the
contact with food in order to begin digesting, and the new-born
lungs need but the contact with air in order to begin to breathe.
The capacity for performing these perpetually repeated visceral
actions is transmitted in perfection. All the requisite nervous
connections are fully established during the brief embryonic
existence of each creature. In the case of lower animals it is
almost as much so with the few simple actions which make up the
creature's mental life. The bird known as the fly-catcher no
sooner breaks the egg than it will snap at and catch a fly. This
action is not so very simple, but because it is something the bird
is always doing, being indeed one out of the very few things that
this bird ever does, the nervous connections needful for doing it
are all established before birth, and nothing but the presence of
the fly is required to set the operation going.

With such creatures as the codfish, the turtle, or the fly-catcher,
there is accordingly nothing that can properly be called infancy.
With them the sphere of education is extremely limited. They get
their education before they are born. In other words, heredity
does everything for them, education nothing. The career of the
individual is predetermined by the careers of his ancestors, and he
can do almost nothing to vary it. The life of such creatures is
conservatism cut and dried, and there is nothing progressive about
them.

In what I just said I left an "almost." There is a great deal of
saving virtue in that little adverb. Doubtless even animals low in
the scale possess some faint traces of educability; but they are so
very slight that it takes geologic ages to produce an appreciable
result. In all the innumerable wanderings, fights, upturnings and
cataclysms of the earth's stupendous career, each creature has been
summoned under penalty of death to use what little wit he may have
had, and the slightest trace of mental flexibility is of such
priceless value in the struggle for existence that natural
selection must always have seized upon it, and sedulously hoarded
and transmitted it for coming generations to strengthen and
increase. With the lapse of geologic time the upper grades of
animal intelligence have doubtless been raised higher and higher
through natural selection. The warm-blooded mammals