PRELIMINARY CONSIDERATIONS. 51 



that it was composed of elements which arrived at 

 different times. 



The great Russian naturalist, the late Professor 

 Brandt, distinguished five phases in the history of the 

 Eurasian mammalian fauna (pp. 249-254). During the 

 first phase an uncertain period of long duration the 

 mammals held intact their position in the northern 

 half of Asia. The Mammoth, the Hairy Rhinoceros, 

 Bison, Musk Ox, Wild Sheep, Reindeer, and perhaps 

 Tigers, Hyaenas, etc., lived then, with numerous 

 peculiar Rodents, under such climatic conditions, 

 according to Brandt, that they were able to extend 

 their range along with tree vegetation to the extreme 

 north of the Asiatic continent This, he thinks, seems 

 to have been the case especially with the Reindeer, 

 Mammoth, Rhinoceros, and Musk Ox. The second 

 phase was characterised by the dispersion of the 

 Northern Asiatic mammalian fauna towards Central, 

 Southern, and Western Europe, and this period lasted 

 until the complete extermination of the Mammoth. 

 The third phase dates from the time when the Mam- 

 moth and the Hairy Rhinoceros had become extinct, 

 whilst the fourth commenced with the disappearance 

 of the Reindeer in Europe, and terminated when the 

 Wild Ox in the feral state had become unknown. 

 Finally, the last phase constitutes the present time. 

 Lartet held similar views, and also believed that 

 Europe was peopled by successive migrations from 

 Asia. 



Botanists have worked at the problem of the 



