skull of the shark gives us a hint of the way in which the modification
took place, and the formation of the skull in the embryo confirms it.

That adult man is devoid of that prolongation of the vertebral column
which we call a tail is not a distinctive peculiarity. The higher apes
are equally without it. We find, however, that the human embryo has a
long tail, much longer than the legs, when they are developing. At
times, moreover, children are born with tails--perfect tails, with
nerves and muscles, which they move briskly under emotion, and these
have to be amputated. The development of the limb from the fin offers no
serious difficulty to the osteologist. All the higher animals descend
from a five-toed ancestor. The whale has taken again to the water, and
reconverted its limb into a paddle. The bones of the front feet still
remain under the flesh. Animals of the horse type have had the central
toe strengthened, for running purposes, at the expense of the rest. The
serpent has lost its limbs from disuse, but in the python a rudimentary
limb-bone is still preserved.

The alimentary system, blood-vessel system, and reproductive system
have been evolved gradually in the same way. The stomach is at first the
whole cavity in the animal. Later it becomes a straight, simple tube,
strengthened by a gullet in front. The liver is an outgrowth from this
tube; the stomach proper is a bulbous expansion of its central part,
later provided with a valve. The kidneys are at first simple channels in
the skin for drainage, then closed tubes, which branch out more and
more, and then gather into our compact kidneys. We thus see that the
building up of the human body from a single cell is a substantial
epitome of the long story of evolution, which occupied many millions of
years. We find man bearing in his body to-day traces of organs which
were useful to a remote ancestor, but of no advantage, and often a
source of mischief to himself. We learn that the origin of man, instead
of being placed a few thousand years ago, must be traced back to the
point where, hundreds of thousands of years ago, he diverged from his
ape-cousins, though he retains to-day the plainest traces of that
relationship. Body and mind--for the development of mind follows with
the utmost precision on the development of brain--he is the culmination
of a long process of development. His spirit is a form of energy
inseparably bound up with the substance of his body. His