a great number of species.

Of all this we can know nothing: but of one thing we may feel assured,
which is that the plantigrade foot is the only one that could have
developed into a grasping organ; such a development being impossible to
the digitigrade or the hoofed animals. One can readily see how the habit
of walking on the sole might tend to a spreading of the toes, in order
to obtain a wider and firmer footing. And it is equally easy to see how
a free and wide motion in the great toe would aid in this result. The
animal may have been at first light in weight and able to support itself
on its unchanged foot, but as it increased in size and weight it would
need a firmer grasp, and the final result of spreading its toes for
this purpose may well have been the opposable great toe.

It must be borne in mind, in this consideration, that the apes differ
from the other tree-dwellers in being destitute of claws. The squirrels,
the opossums, and other arboreal animals have sharp claws, by whose aid
they can easily cling to the surface of the bark-covered boughs. The
nails of the apes are incapable of affording them this service, and it
is not easy to perceive how a foot like theirs could become adapted to
locomotion in the trees otherwise than by the gaining of mobile action
and grasping power in the toes.

The existing habits of the ape tribe lead us to the conclusion that the
ancestral animal may have soon begun to seek support from upper limbs.
The plantigrade foot is one capable of readily curving into an organ of
support, and in the case of the forefoot the toes would tend to spread
and gain flexibility of motion, and the first toe to become opposable to
the others and yield a more complete grasping power. It does not seem
difficult to comprehend, from this point of view, how the feet of a
five-toed plantigrade animal may in time have developed into grasping
organs, since there would be required only an increased flexibility of
the joints, and a wider and fuller movement of the great toes. That such
a change took place in this instance the facts appear to indicate, the
most simple and probable explanation of the development of the grasping
power in the hands and feet of the ape being seemingly that given above.

The relation of the lemurs to the apes is not clearly defined. It may be
an ancestral one, or the two animals may represent distinct lines of
descent. In the latter case we would have two lines of animal evol