In Central Europe the climatic conditions can have been only slightly different. During the middle Tertiary Period palms grew in Switzerland; and even at the end of the Tertiary Period, as it was slowly passing into the Drift Era, the climate in Central Europe was still warmer than now, being much like that of Northern Italy, and its protected west coast the Riviera. There was also a rich flora, partly evergreen, and a fauna adapted to such mild surroundings. Even in the oldest (Preglacial) strata, and again in the middle (Interglacial) strata of the Central European drift, there was still an abundant plant-growth requiring a temperate climate, at any rate not more severe than Central Europe possesses at the present day. Our chief forest trees grew even then--the pine, fir, larch, and yew, and also the oak, maple, birch, hazel, etc. On the other hand, Northern and Alpine forms are absent among the plants. The same holds good of the animal world, which was certainly much farther removed than the plant world from the conditions prevailing now. The gigantic forms--the elephant, rhinoceros, and hippopotamus--appear particularly strange to us, as also the large beasts of prey--the hyena, lion, etc. But besides these, and the giant deer with its powerful antlers, and two large bovine species--the bison and the urus--there were also the majority of the present wild animals of Central and Northern Europe that were originally natives--as the horse, stag, roe, wild boar, and beaver, with the smaller rodents and insectivora, and the wolf, fox, lynx, and bears, of which last the cave-bear was far larger than the present brown bear, and even than the Polar and grizzly bears. We have sure proofs that through a decrease in the yearly temperature a glacial period set in over Europe, North Asia, and North America, burying vast areas under a sheet of ice, of the effect and extent of which Northern Greenland, with its ground-relief veiled in inland ice, can give us an idea. The immediate consequence of this total climatic change was an essential change in the fauna. Forms that were not suited to the deteriorated climate, that could neither stand it nor adapt themselves to it, were first compelled to retire, and then were exterminated. This fate befell the hippopotamuses, and also one of the two elephant species, _Elephas antiquus_, with its dwarf breeds in Sicily and Malta, probably thus developed by this retreat; then the rhinoceros-like _Elasmotherium_, a species of beaver; the _Trogontherium_, and the powerful cat _Machairodus_ or _Trucifelis_, which still lived in England, France, and Liguria during the Drift Period. Other animals, like the lion and hyena, withdrew to more southerly regions, not affected by the increasing cold and more remote from its effects. [Sidenote: The Older Drift Animals]