THE GLACIAL THEORIES, 
103 
such strata are unknown, at least in Europe. A further explanation of 
the occurrence of a „mixed fauna“ has been given by other specialists 
assuming that some single specimens of the Lemmings remained here- 
and-there on the path of their companions. I am fully convinced of 
the absolute wrong of this supposition as well. Even if some specimens 
belonging to arctic species might have settled the respective territory in 
the course of their migration, they have never been permanent inhabitants 
of the plains, but took their refuge into the high mountains, offering 
them convenient climatic conditions. 1 
I have already pointed out the fact that the time in which the 
formation of the steppe fauna took place synchronises with that of the 
regression of the Lemmings ; the arctic and steppe fauna were only 
Fig. 7. The easternside of the gypsum-pit at Thiede near Braunschweig. (After Nehring.) 
separated after the ice having withdrawn as far as to leave behind it a 
territory the extension and the biological conditions of which sufficiently 
secured the existence of the Lemmings. This may be expressed also by 
the following terms : The psychrophil species emigrated into the coldest 
1 Dr. St. J. Bolkay, Additions to the Herpetology of the Western Balkan 
Peninsula. (Glasnik Zemaljskog Muzeja u Bosni i Hercegovink Sarajevo 1919. p. 37.) 
„These species were distributed probably all over the Balkan Peninsula during the 
glacial period and after the definite withdrawel of the glaciers, took their refuge in 
the varions high mountains. The coasts, valleys and plains having been populated 
again with thermophil species originating from southern and south-eastern countries.“ 
