SECT, xxvii.] DISTRIBUTION OF ANIMALS. 307 



number of species composing the other vegetable families, 

 may be estimated with considerable accuracy. 



Various opinions have been formed on the original or 

 primitive distribution of plants over the surface of the globe ; 

 but, since botanical geography became a regular science, the 

 phenomena observed have led to the conclusion that vege- 

 table creation must have taken place in a number of dis- 

 tinctly different centres, each of which was the original seat 

 of a certain number of peculiar species, which at first grew 

 there and nowhere else. Heaths are exclusively confined to 

 the Old World, and no indigenous rose-tree has ever been 

 discovered in the New, the whole southern hemisphere being 

 destitute of that beautiful and fragrant plant. But this is still 

 more confirmed by multitudes of particular plants having an 

 entirely local and insulated existence, growing spontaneously 

 in some particular spot, and in no other place ; for example, 

 the cedar of Lebanon, which grows indigenously on that 

 mountain, and in no other part of the world. On the other 

 hand, as there can be no doubt but that many races of plants 

 have been extinguished, Sir John Herschel thinks it possible 

 that these solitary instances may be the last surviving rem- 

 nants of the same groups universally disseminated, but in 

 course of extinction, or that, perhaps, two processes may be 

 going on at the same time ; " some groups may be spreading 

 from their foci, others retreating to their last strong holds." 



The same laws obtain in the distribution of the animal crea- 

 tion. The zoophite (K 215), occupying the lowest place in 

 animated nature, is widely scattered through the seas of the 

 torrid zone, each species being confined to the district best 

 fitted to its existence. Shell-fish decrease in size and beauty 

 with their distance from the equator ; and, as far as is known, 

 each sea has its own kind, and every basin of the ocean is 

 inhabited by its peculiar tribe of fish. Indeed, MM. Peron 

 and Le Sueur assert that, among the many thousands of 

 marine animals which they had examined, there is not a 

 single animal of the southern regions which is not distin* 



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