The earlier rocks contain fossils of the lower forms of life, like seaweed and simple creatures in shells; in succeeding rocks come the fishes—the first living things with a backbone—primitive forms being followed by more elaborate types; in later strata are found the fossil remains of the amphibians; following these, in rocks higher up, are the relics of the reptiles; then come the reptile-birds, and in still later rocks appear the primitive mammals; onward and upward rises the spiral of life, and in yet later rocks occur placental mammals—early horses, marmosets and lemurs; higher still, the strata imprison fossil cats, pigs, elephants, antelopes and apes; and over the fossil remains of all other creatures, in the rock-crust of the earth, as is required by the facts of biological unfoldment, lie the fossilized forms of man-like apes and men. Thus geology confirms the conclusions of biology. [Illustration: FIG. 31.—A RESTORATION OF THE NEANDERTHAL MAN. This picture is a retouched photograph taken of a model made by Guernsey Mitchell according to instructions of Prof. Henry A. Ward of Chicago. Reprinted with the permission of The Open Court Publishing Co.] In Fig. 32 we have a series of fossil heads from different periods in the ascending geological order, illustrating the gradual development of the elephant’s tusks and trunk. See how the tusk, beginning as an upper tooth in the Eocene period when the elephant was no larger than a rabbit, gradually lengthens as the periods pass, until we get, after millions of years, the great curved tusk of the elephant of to-day. The growth of the trunk kept pace, of course, with the extension of the tusks. On the left side may be seen the gradual and corresponding modification of the elephant’s teeth. The horse, the noblest of the quadrupeds, has been evolved from a small five-toed animal. The Eohippus, the “dawn horse,” whose fossil remains have been found in the lower Eocene rocks, was no bigger than a small fox (Fig. 33). It had four toes and a splint on each front foot, and three toes and two splints on each hind foot—which proves that its ancestors had five toes on each foot. The “dawn horse” was a browsing animal. Restorations of this little horse, and of the larger three-toed horse that followed him, are now familiar figures in natural history museums. Evolution, you see, is not a figment of somebody’s imagination; it is, rather, the compelling, common sense interpretation of the facts of nature. [Illustration] [Illustration] [Illustration: FIG. 32.—EVOLUTION OF THE PROBOSCIDEA. On the right, a series of skulls; on the left, last lower molar. Reprinted with the permission of the author and publishers from Prof. William B. Scott’s “A History of Land Mammals in the Western Hemisphere.” The Macmillan Co., New York.]