ITS FAUNA. 49 



essentially distinct from the Coralline zone, which ranges 

 from 90 to 300 feet, and is the great theatre of marine life; 

 while beyond this lies the Coral zone, the region of the 

 strong calcareous corals extending from 300 to 600 feet in 

 depth from the shore line. But it is not alone to climate 

 and external conditions that we must look for the variety 

 and distribution of animal life. There is an aboriginal 

 diffusion of different tribes and families from certain centres 

 and over certain areas, for which science can as yet offer no 

 satisfactory reason. Thus, why should the giraffe, or ostrich, 

 or hippopotamus, be restricted to the continent of Africa, 

 while the forests, and plains, and river-swamps of South 

 America enjoy the same tropical sun, and seem every way 

 equally adapted to identity of vitality ? The pampas of 

 America, as has been proved by experience, are as well 

 fitted for the increase of the horse as the plains of Europe 

 or the steppes of Tartary; and yet, till man carried him 

 thither a few hundred years ago, no horse of the current 

 epoch existed there. The ornithorliynchus burrows only 

 in the river banks of Australia ; the apteryx is unknown 

 beyond the limits of New Zealand ; the sloth is confined 

 to the tropical forests of America the armadillo to the 

 same region ; and not one of the Old World monkeys is 

 identical with any of those of the New. Nor is it alone 

 the terrestrial tribes that are thus limited and restricted ; 

 the aerial and aquatic, though possessing superior facilities 

 for dispersion, are equally circumscribed, each within its 

 own geographical habitat. The humming-birds nutter only 

 over the flowers of the New World ; the pheasants are 

 unknown beyond the coverts of the Old ; the shark-like 

 cestraciont frequents alone the waters of the Southern 

 Pacific ; and the trigonia never carries its shell beyond the 

 shores of Australasia. Such restrictions w 7 e cannot explain 

 unless by ascribing them to independent centres of creation, 



