GEOGRAPHICAL DISTRIBUTION OF ANIMALS 1541 



mata, the elephant, the rhinoceros, the hippopota- 

 mus, the horse, the zebra, and the ass are unknown 

 to the native zoology of the lands lying west of the 

 Atlantic. The elephant, and also the rhinoceros, be- 

 long to Asia and Africa (the species being different 

 in the case of either continent), the hippopotamus 

 is African only: the zebra (with its kindred species, 

 the quagga) is also peculiar to Africa. Both the 

 horse and the ass probably came originally from Asia. 

 Of the Quadrumana, which are numerously repre- 

 sented in the zoology of either hemisphere, the spe- 

 cies (and, in most cases, the genera) are distinct. 

 Again, the opossums of the New World belong to an 

 order (the marsupial) which is altogether unrepre- 

 sented in the three continents of the Old World, but 

 which exhibits its fullest development in the Austra- 

 lian division of the globe. Numerous other instances 

 might be adduced, but these will suffice. They serve 

 to show that, in the case of animals as of plants, par- 

 ticular regions constitute centres of particular forms 

 of life, which thence spread, within certain limits, 

 around, still leaving to each such region its strongly 

 marked and typical characteristics in such regards. 



Europe exhibits, in its indigenous zoology, a char- 

 acter less marked and distinctive than belongs to 

 other divisions of the globe. This is in some degree 

 the result of its dense population, and the consequent 

 diminution in the number of wild species, but in a 

 more special manner results from its conditions of 

 geographical form and position. Europe is less 

 a continent in itself than an outlying portion of 

 the vast and unbroken mass of the Asiatic continent. 



