INTRODUCTION.
By the Evolution of Life we mean the slow and gradual development of life as distinguished from its special and sudden creation; that plants and animals are the modified descendants of pre-existing organisms, not the unchanged posterity of similar forms of life originally specially created. Let us illustrate our meaning by considering the origin of a common animal like the Horse. According to the creation hypothesis, all horses are the descendants of a pair of horses, originally, specially created. Supposing the Evolution theory, however, to be true, the Horse is the modified descendant of an extinct species of Horse, the Hipparion. Preceding the Hipparion there lived the Anchitherium, whose organization bears the same relation to the Hipparion that the Hipparion's does to that of the Horse; while in a still earlier period we find in the Paleotherium the ancestor of the Anchitherium. But the Rhinoceros and the Tapir are also nearly related to the Paleotherium. We see, therefore, why all naturalists are agreed in regarding the Horse, Rhinoceros, and Tapir as the representatives of one group. For, if these animals are the posterity of a common ancestor, it is natural that their organization should have much in common. Through extinct forms, like the Xiphodon and Anthracotherium, the Ruminating animals, the Pig, and the Hippopotamus, are linked with the Anoplotherium; while glancing at Tree VII. we see that the Paleotherium and Anoplotherium are
