8 THE WANDERINGS OF ANIMALS [CH. 



the Sahara, formerly a marine basin, was peopled by 

 immigrants from the neighbouring countries, and 

 these became new animals by adapting themselves 

 to the new environment ; the agreement in coloration 

 between the desert and its fauna is 'une harmonic 

 post-etablieV They did not survive because they 

 happened to be of desert-colour, but assumed that 

 colour because they found themselves in a desert. 

 He also discussed, besides similar questions, the 

 Isthmus of Panama with regard to its having once 

 been a strait. A strong proof of the new influence 

 upon this French scientist is the following sentence : 

 1 As the various parts of the world successively were 

 formed and became habitable their respective con- 

 temporaneous faunas spread by radiation, each from 

 its centre, and became modified according to the 

 local physical conditions.' 



In 1866 appeared Andrew Murray's Geographical 

 Distribution of Mammals, an important work, illus- 

 trated with 101 coloured maps, the first of its kind 1 . 

 Like Forbes he did not shrink from assuming 



separating S. America as well as Australia from the rest of the world. 

 Of far reaching influence was also the excellent Zoo-geographical 

 sketch Ueber die Herkunft unserer Thierwelt by the Swiss Palaeonto- 

 logist L. Riitimeyer, published at Basel in 1867. 



1 The earliest maps dealing with our subject seem to be those in 

 H. Berghaus' Physikalischer Atlas: Thiergeograpkie, Gotha, 1852. 

 In the third edition, 1887, this has been enlarged into an Atlas der 

 Tierverbreitung , by W. Marshall. 



