1528 THE STORY OF THE UNIVERSE 



ing temperate latitude of America. But no indi- 

 viduals of the rhea have remained in the prairies or 

 in any part of North America they are limited to 

 the middle and southern division of the South 

 American continent. And now, finally, consider the 

 abode of the little apteryx at the Antipodes, in the 

 comparatively small insulated patch of dry land 

 formed by New Zealand. Let us call to mind its 

 very restricted means of migration the wings re- 

 duced to the minutest rudiments, the feet webless 

 like the common fowls, its power of swimming as 

 feeble! How could it ever have traversed six hun- 

 dred miles of sea that separate it from the nearest 

 land intervening between New Zealand and Asia? 

 How pass from the southern extremity of that con- 

 tinent to the nearest island of the Indian Archipel- 

 ago, and so from member to member of that group 

 to Australia and yet leave no trace behind of such 

 migration by the arrest of any descendants of the 

 migratory generations in Asia itself, or in any island 

 between Asia and New Zealand? 



If these facts are inexplicable on the hypothesis 

 of the dispersion of the species of the air-breathing 

 animals from a single Asiatic centre, we must next 

 endeavor to collect analogous facts and classify 

 them, and so try to explain intelligibly, that is agree- 

 ably with the facts, the true law or cause of the 

 actual geographical distribution of animals. 



The laws of geographical distribution, as affect- 

 ing mammalian life, have been reduced to great ex- 

 actness by observations continued since the time of 

 Bufifon, who first began to generalize about a century 



