Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 18. (Budapest 1921)
Éhik, Gy.: The glacial-theories in the light of biological investigation
94 Dr. J. í'. HIK the extending ice reaching the limits of northern Europe. The Pleistocene might be divided into three principal biological phases, i. e. : the preglacial, the glacial and the postglacial period. The preglacial period (fig. 2.) commences simultanously with the beginning of te Pleistocene and lasts until the ice having reached its largest extension. A fauna of three different kinds characterizes this period on the northern hemisphere: a cold polar fauna close to the ice, containing typical tundra elements, followed by a more southern thermophil fauna, characterized by Pliocene elements, and at last by a southernmost tropical fauna. The glacial period (fig. 3.) constitutes the largest extension of the ice, beginning its withdrawel probably only after a long lapse of time. The arctic fauna and flora was then again removed in a southern direction forming a biological zone including the northern parts of Hungary, while we find the elements of the thermophil fauna occupying the southern parts of Hungary and extending as far as North-Africa, the tropical biosphere beeing limited to South-Asia and Africa. Ice and snow covered the northern parts of Europe in the midst of which no life was possible. The postglacial period (fig. 4.) begins by the withdrawel of the ice, terminating by this latter having retreated to the polar circle. At this period we find the fauna represented by new elements, viz. by the ,,steppe"-forms, having settled the territory from which the ice withdrew. Let us now at last examine the present biogeographical map of Europe (fig. •'>). The most striking on this map is the occurrence of forest-zones on the spots where an oceanic climate is present, the steppe fauna beeing limited to the eastern regions. If I ought to demonstrate the faunistical alterations briefly sketched above by a diagram, a „biogeological-profile" (fig. 6.) would be the result, setting forth the following particularities : 1. About at the middle of the Tertiary the ice is beginning to extend from the Poles towards the Equator, this extension lasts till the middle of the Pleistocene, and after having reached its southernmost limit, withdraws in a northern direction. 2. In the beginning there is no Polar fauna only some temperate types having evolved from the earlier thermophil forms ; it is but later on that the true arctic fauna has been developed, originating thus from the temperate one, in accordance with the gradual extension of the ice. In as much as the life of these arctic animals depended on a cold climate, they followed later on the withdrawing ice. 3. The mass of the arctic fauna advancing southwards drove the thermophil and this again the tropical fauna, to still southernmore regions.
