446 



EXTINCTION OF SPECIES. 



[Ch. XLII. 



most im 



r 



from 



made 



be others of a distinct nature^ sucli as the conversion of a 



isthmns 



This sxDace, previously occnpied by terrestrial plants and 

 animals would be immediately delivered over to the aqnatic ; 

 a local revolution which might have happened in innumer- 

 able other parts of the globe, without being attended by any 

 alteration in the blending together the species of two distinct 



provinces 



ma 



/ 



communication 



between two seas which are now inhabited by fish, moUusks, 

 crustaceans, and other aquatic tribes nearly all of them speci- 

 fically distinct. A contest would take place between thousands 

 of allied species which in the course of time would give rise to 



predominance of some 



of others. 



Morocco 



submarine 



uniting the islands of Bali and Lombok. 



described,^ the Mediterranean fauna would be separated 

 from that of the Atlantic, and there would be a fusion of the 

 terrestrial plants of Northern Africa Avith those of Southern 

 Europe. Or we may imagine a land communication to be 

 caused by volcanic outbursts in the straits of Lombok, f 



This would bring 

 about a conflict between the land-birds, insects, and plants 

 of the Indian and Australian provinces, which could not 

 fail to add to the numerical predominance of some species 

 at the expense of others, while some might be exterminated. 

 But even such fluctuations would to a human observer appear 

 sloAV in the extreme, because a communication formed by a 

 new volcanic island will not simply take thousands of years, but 

 perhaps thousands of centuries, for its accomplishment, and 

 few of the species capable of profiting by the removal of the old 



com 



)/ tlxe range of one species alters that of 



In 



I 



eference to the extinction of species it is important to bear 



* See above, Vol. I. p. 562. 



t See Map, fig. 132, p. 347 



I 

 I 



