[Illustration: _Sincerely Yours Henry Drummond._]
One of the most humorous sights in nature, less common in America than
Europe, is a snail wandering about with a shell on its back. The
progenitors of snails once lived in the sea, and when they evolved
themselves ashore they carried this relic of the water with them,--an
anomaly which, seen to-day, seems as ridiculous as if one were to meet
an Indian in Paris with his canoe on his back. But there are more
animals besides snails that once lived in the water. If embryology is
any guide to the past, nothing is more certain than that the ancient
progenitors of Man once lived an aquatic life. As the traveller,
wandering in foreign lands, brings back all manner of curios to remind
him where he has been--clubs and spears, clothes and pottery, which
represent the ways of life of those whom he has met, so the body of
Man, returning from its long journey through the animal kingdom,
emerges laden with the spoils of its watery pilgrimage. These relics
are not mere curiosities; they are as real as the clubs and spears,
the clothes and pottery. Like them, they were once a part of life's
vicissitude; they represent organs which have been outgrown; old forms
of apparatus long since exchanged for better, yet somehow not yet
destroyed by the hand of time. The physical body of Man, so great is
the number of these relics, is an old curiosity-shop, a museum of
obsolete anatomies, discarded tools, outgrown and aborted organs. All
other animals also contain among their useful organs a proportion
which are long past their work; and so significant are these rudiments
of a former state of things, that anatomists have often expressed
their willingness to stake the theory of Evolution upon their presence
alone.
Prominent among these vestigial structures, as they are called, are
those which smack of the sea. At one time there was nothing else in
the world but water-life; all the land animals are late inventions.
One reason why animals began in the water is that it is easier to live
in the water--anatomically and physiologically cheaper--than to live
on the land. The denser element supports the body better, demanding a
less supply of muscle and bone; and the perpetual motion of the sea
brings the food to the animal, making it unnecessary for the animal to
move to the food. This and other correlated circumstances call for far
less mechanism in the body, and, as a matter of fact, all the simplest
forms of life at the present day are inhabitants of the water.
[Illustration: "BALANOGLOSSUS" (AFTER AGASSIZ), AND LARGE SEA LAMPREY
(AFTER CUVIER AND HAECKEL), SHOWING GILL-SLITS.--FROM "DARWIN AND AFTER
DARWIN" BY ROMANES.]
A successful attempt at coming ashore may be seen in the common worm.
The worm is still so unacclimatized to land life that instead of
living on the earth like other creatures, it lives _in_ it, as if it
were a thicker water, and always where there is enough moisture to
keep up the traditions of its past. Probably it took to the shore
originally by exchanging, first the water for the ooze at the bottom,
then by wriggling among muddy flats when the tide was out, and
finally, as the struggle for life grew keen, it pushed further and
further inland, continuing its migration so long as dampness was to be
found. Its cousin the snail, again, goes even further, for it not only
carries its shell ashore but when it cannot get moisture, actually
manufactures it.
[Illustration: EMBRYOS SHOWING GILL-SLITS.--FROM HAECKEL's "EVOLUTION OF
MAN."