Page:Popular Science Monthly Volume 15.djvu/32

 seldom used for flight, would degenerate as time passed. The later advent of man, in turn, has exterminated certain races of the wingless birds—such as the Dodo (Fig. 6) and Solitaire (Fig. 7) in Mauritius and Rodriguez—while the wingless and giant Dinornis of New Zealand and its contemporaries have probably been hunted to the death of their species by their human co-tenants of these strange lands.

The ascent to the quadrupeds brings in review before us still more striking illustrations of the apparently incomplete rendering of the structures of animal life. No better instance of the "rudimentary organs" of the naturalist can be found than in the group of the whales, and more especially in the species from which we obtain the commercial whalebone and oil—the Greenland or right whale. This whale possesses no teeth in its adult state, but before birth teeth are found in the gum. These teeth, however, are gradually absorbed, and utterly disappear from the jaws, the adult whale possessing, as is well known, a great double fringe of whalebone-plates depending from the palate. The same remark holds good of the unborn young of ruminants, or animals which "chew the cud"; these animals in their adult state possessing no front teeth in the upper jaw, but in their immature condition developing



these organs—which, by the way, never cut the gum—only to lose them by a natural process of absorption. Now, here there can be no question of use; and certainly no adequate explanation of their occurrence exists, save that which regards these fœtal teeth as the remnants of structures once well developed in the ancestors of the whale-bone whales and ruminants. To this supposition the evidence—avowedly incomplete—obtained from geology gives no contradiction, even if it does not by any means supply the "missing links" in an adequate fashion. We do know that among the oldest of the great leviathans of the past was the Zeuglodon, which had teeth developed much in excess of anything we find represented in the dental arrangements of the