IMMIGRATIONS, Animal and Vegetal, into America began in early geological times. At the dawn of the Age of Mammals, when the great Mesozoic reptiles were disappearing, and the Tertiary Era introduced the dominance of mammalian and other types of animal life, that became more and more modernized as time advanced, the circumpolar regions of the Northern Hemisphere seem to have been a con tinuous mass of land. The climate • was mild, and animals and plants 'had free space in which to wander right around the northern world. The origins of the strange primitive creatures then prevalent are unknown; but their scanty fossil remains show Heir substantial identity in Europe, Asia and America. Before long— as geological time is reckoned—changes in the restless crust of the earth caused separation of North America from both Asia on the west and Europe on the east, and fossils of the Mid dle Eocene show that local types speedily de veloped in every continent. This independent and divergent adaptive modification continued until the Eocene had merged into the Oligocene, as shown by rocks of the White River forma tion in eastern Wyoming. Land connection had been restored by a lifting of the Bering Sea region, and an isthmus thus formed between Alaska and Siberia. By this bridge came new forms from Asia, while American migrants wandered into the Old World; but the inter change was very limited, bringing to us only certain small forerunners of the sabre-toothed cats," of the mustelines of some early creodonts (as Hyamodon), and of primitive rodents. At this time were introduced also the anthracotheres, short-legged, somewhat swine like, hoofed animals, which have no near rela tives in the modern world, but had been previ ously well represented in Europe. There came also the earliest of the horses (Eohippus), the first opossums and a few others. The Oligo cene was followed by the Miocene, a period of mild climate and wide-spread volcanic activity, in which land connection with Siberia, long interrupted, appears to have been restored, and when the first small forms of proboscidians en tered this continent, on which subsequently they developed so extensively. °The place of origin and ancestry of these says Prof. W. B. Scott, ewere long exasperating puzzles. Appearing suddenly in the Miocene of Europe and America, in which regions nothing was known that could, with any plausi bility, be regarded as ancestral to them, they might as well have dropped from the moon for all that could be told respecting their history.
The exploration of Eocene and Oligocene beds of Egypt has dispelled the mystery, and shown that Africa was the original home of the group.° Pliocene time witnessed important in troductions from both Asia and South America, where an independent fauna was developing. The most strilang novelty, probably, were the bears—a distinctly Old World family. Among the notable importations in the next, or Pleistocene, period, were the antelopes and the bison. These instances of animal invasion in the distant past are only a few of the list that might be compiled were palzontologists as cer tain of the foreign origin of some groups as they are of others. More important to us than this, however, is consideration of the invasions of animals and plants within historic times. Horses, cattle, sheep, dogs, cats and poultry, were brought in by the conquerors of tropical America, and by the colonists of its northern coasts, and these aids to agriculture, hunting and housekeeping were too quickly followed by invading foreigners of a harmful character. In the same way grain-plants, forage-plants, garden vegetables, fruits and ornamental trees, shrubs an flowers, came into the country from all parts of the world. Some, unsuited to the conditions, died out; or, like tea and indigo, proved unprofitable and have been neglected. With the ships that brought these beneficent ad ditions to our fauna and flora came many un welcome visitors—true invaders in the modern sense of the word. Weeds innumerable began with the first settlements. Most of them were accidental importations, in seed, or in the dis charged ballast of ships, or were attached to trees, shrubs and plants imported. Some were garden-flowers, controllable and harmless at home, but here flourishing' inordinately and spreading into fields and highways; others, weeds and grasses pestiferous everywhere; others the molds, smuts and similar bacteric or fungoid diseases afflicting grains and fruits. It was long before the government took any pre cautions against such evils.