A number of the most characteristic species of the former sections of the Drift Period are already absent in the earliest post-Glacial deposits; the fauna approaches nearer and nearer in its composition to that of the present day. The inland ice-masses and gigantic glaciers began to melt away, and gradually retired to the present limits of the glaciation that forms the remains of the Glacial Period of the Drift. The animal forms of the beginning of the post-Glacial Period are still living, and the plants characterising this final stage of the Drift Period are still growing on the borders of the ice at the present day. In the post-Glacial Period a few Northern forms--such as the reindeer, lemming, ringed lemming, glutton, zizel, whistling hare, and jumping mouse--still retained for a time their habitats in Central Europe. Part of the Drift fauna--as the horse, wild ass, saiga antelope, and Asiatic porcupine--concentrated again in the Asiatic steppes, from which they had formerly won their territory of the Drift Period; the specific Glacial forms--the reindeer and his above-mentioned companions--followed the retreating ice-masses into the Far North, and even into Polar regions. Another part--the specially Alpine forms, such as the ibex, chamois, marmot, and Alpine hare--migrated with the Alpine glaciers into the high valleys of the Alps, where they could continue the life they had led in the lowlands during the Glacial Period. The mammoth, woolly-haired rhinoceros, and cave-bear are extinct. The present-day mammalian fauna of Europe and North Asia accordingly bears a comparatively young character; during the Drift, and especially in consequence of the Glacial Period, it underwent the most considerable transformations. [Sidenote: Coming of Man upon the Scene] It is in the middle of this great drama of a gigantic animal world struggling and fighting for its existence with the superior powers of Nature, during the Interglacial period of the Drift, that man suddenly appears upon the scene in Europe like a _deus ex machina_. Whence he came we do not know. Did he make his entrance into Europe in company with the Drift fauna that immigrated from Central Asia, or have we to seek his original home in the New World? [Illustration] [Illustration: THE FIRST TENANTS OF THE WORLD: CREATURES THAT LIVED BEFORE MAN This page represents the most typical of the giant creatures that inhabited the world before man. With possibly one exception, they had disappeared before man came and, through long centuries, slowly won dominion over the earth. ] [Illustration: THE WORLD BEFORE HISTORY--II Professor JOHANNES RANKE ] THE APPEARANCE OF MAN ON THE EARTH [Sidenote: The Mystery of a Human Skull]