2/2 HISTORY OF THE EUROPEAN FAUNA. 



while others occur in Central and Northern Europe, 

 scarcely in the South, and not at all in the 

 larger Mediterranean islands or in North Africa. 

 This appears to me to indicate that the late comers 

 from the east found that geographical changes had 

 taken place in Southern Europe which prevented 

 them from following the same track as the older 

 immigrants. They were now obliged to turn directly 

 northward and then westward. It may be asked, 

 why should not the earlier migrants have taken the 

 same route? This question will be answered imme- 

 diately. Meanwhile it should be clearly understood 

 that there probably was an older and a newer migra- 

 tion from the east. The Oriental genera from 

 whose general range we know that they must be 

 very ancient indeed, such as Mantis and Bacillus 

 are almost invariably confined to Southern Europe. 

 There they are frequently found on some of the 

 Mediterranean islands. The earlier migrants there- 

 fore went westward and the later ones north- 

 ward. 



Let us now inquire a little into the reasons why 

 such different courses were pursued by the migrants 

 why the Oriental migration divided into two 

 streams, an older and a newer. 



During early Tertiary times, and probably through- 

 out the Miocene and Pliocene Epochs, the ^Egean 

 Sea did not exist. From the island of Crete to the 

 Peloponnesus, and from Asia Minor to Thessaly 

 and Macedonia, stretched a vast and fertile plain 



