een tried
which in the end have proved most successful, giving us animals with the
speediest movements of any animals except the creatures of the air.

[Illustration: A Hunter]

The success which has been attained in our ordinary large herbivora, and
which has made them competent to evade the chase of the beasts of prey,
has been accomplished by reducing the number of the toes, giving the
strength of the aborted parts to increase the power of those remaining.
The result is the formation of two great groups, the double-hoofed
forms, including the pigs, deer, cattle, sheep, and their kindred, and
the single-toed species, of which our horse is the foremost example. In
the reduction of the number of toes, different plans were followed in
each of these groups. In the cloven-hoofed forms, a single toe first
disappeared, leaving but four; then the two outer of these were aborted,
leaving two nearly equal digits. In the series of the horse, where we
can trace the change more clearly, we find the earliest form five-toed,
but the outer and inner digit shrunken so as to become of little use.
This condition of the creature in the early Tertiaries gives us the
beginning of the equine series, and shows that far away as the creature
is now from ourselves, it originated from the main stem of mammalian
life, from which our own forms have sprung. In the next higher stage in
time, and likewise in development, we find these lessened toes at their
vanishing point, and two of the remaining digits, lying on either side
of what corresponds to the middle finger in our own hands, beginning to
shrink in length and volume, while the central toe becomes larger and
stronger than before. Last in the series we come to our ordinary equine
form, in which nothing is left but the single massive extremity, though
the remnants of two of the toes can be traced in the form of slender
bones known as splints, which are altogether enclosed within the skin
which wraps the region about the fetlock joints.

As if it were to show to us the history of this marvellous organic
achievement, nature now and then, though seldom--perhaps not oftener
than one in ten million instances--sends forth a horse with three hoofs
to each leg. Two of these are small and lie on either side of the
functioning extremity. Each of these hoofs is connected with a
splint-bone which has in some way suddenly become reminded of its
ancient use, and develops in a manner to imitate the creature