e backbone, which is
certainly one of the essential features of the vertebrate race. The
notochord is the supporting axis of the pioneer backboned animals,
namely the Lancelets and the Round-mouths (Cyclostomes), such as the
Lamprey. They have no backbone in the strict sense, but they have this
notochord. It can easily be dissected out in the lamprey--a long gristly
rod. It is surrounded by a sheath which becomes the backbone of most
fishes and of all higher animals. The interesting point is that although
the notochord is only a vestige in the adults of these types, it is
never absent from the embryo. It occurs even in man, a short-lived relic
of the primeval supporting axis of the body. It comes and then it goes,
leaving only minute traces in the adult. We cannot say that it is of any
use, unless it serves as a stimulus to the development of its
substitute, the backbone. It is only a piece of preliminary scaffolding,
but there is no more eloquent instance of the living hand of the past.

One other instance must suffice of what Professor Lull calls the
wonderful changes wrought in the dark of the ante-natal period, which
recapitulate in rapid abbreviation the great evolutionary steps which
were taken by man's ancestors "during the long night of the geological
past." On the sides of the neck of the human embryo there are four pairs
of slits, the "visceral clefts," openings from the beginning of the
food-canals to the surface. There is no doubt as to their significance.
They correspond to the gill-slits of fishes and tadpoles. Yet in
reptiles, birds, and mammals they have no connection with breathing,
which is their function in fishes and amphibians. Indeed, they are not
of any use at all, except that the first becomes the Eustachian tube
bringing the ear-passage into connection with the back of the mouth, and
that the second and third have to do with the development of a curious
organ called the thymus gland. Persistent, nevertheless, these
gill-slits are, recalling even in man an aquatic ancestry of many
millions of years ago.

When all these lines of evidence are considered, they are seen to
converge in the conclusion that man is derived from a simian stock of
mammals. He is solidary with the rest of creation. To quote the closing
words of Darwin's _Descent of Man_:

We must, however, acknowledge, as it seems to me, that man with all
his noble qualities, with sympathy which feels for the most debased,
wi