94 
Dr. J. ÉHIK 
the extending ice reaching the limits of northern Europe. The Plei¬ 
stocene 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 thermo- 
phil fauna, characterized by Pliocene elements, and at last by a southern¬ 
most 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 direc¬ 
tion forming a biological zone including the northern parts of Hungary, 
while we find the elements of the thermophil fauna occupying the south¬ 
ern 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. 5). 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 Ecfuator, 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. 
