Those animals which have their home in the latter area, I have named Orientals, though it must be remembered that they need not necessarily have come from what is known among zoologists as the "Oriental Region." The terms "Oriental animals" and "Oriental migration" are used here in a wider sense, and include even those species which reached Central and Northern Europe from South-Eastern Europe. It is astonishing, what a vast number of both vertebrate and invertebrate animals can be traced back to this Oriental migration. Great tracts of Europe were repeatedly submerged beneath the sea during Tertiary times, and on their re-appearance were formed into green fields and pastures new for the rich Asiatic fauna, which was ever ready to flood the neighbouring continent. This went on, and not for a comparatively short space of time, as in the case of the Siberian invasion; the immeasurable ages which passed, whilst several of the Tertiary epochs dawned upon Europe, witnessed an almost constant stream of Asiatic immigrants pouring in upon us. Europe returned her own products in exchange, but they must have been scanty in comparison to the enormous number of species which have undoubtedly originated in Central and Southern Asia. Very many of the widely distributed forms in the British Islands are of Oriental origin. Among these are also the cosmopolitan species, such as the Barn Owl (_Strix flammea_) and the Painted Lady Butterfly (_Vanessa cardui_). A great number of our British Mammals, Birds, Butterflies, and Beetles have come to us with the Oriental migration. But, as I shall explain in the special chapter devoted to it, the earlier migrants from the south-east found their northward progress barred by a great sea which stretched through Central Europe from west to east. The Mediterranean was then divided into two smaller basins. On their arrival in Greece, which was then connected with Asia Minor and Southern Italy, the Oriental migrants seem to have turned westward, skirting the shores of the Mediterranean. When they finally reached Spain, many then changed their course northward (see Fig. 5, p. 117) and wandered to the British Islands with the Lusitanian animals which came from South-Western Europe.