496 



liv- in the midst of the waters. In passing from the coast ,,t 

 Europe into the Indian Ocean, and from tliis last into tin- 

 seas of America, we meet with fishes, molluscs. cru>tacea. and 

 zoophytes peculiar to each of those parts of the sea. This 

 localization of species, \\hetheraquaticorterrestrial, is so well 

 marked that a naturalist a little experienced cannot mistake 

 at the very first sight the origin of zoological collections made 

 in one or other of the great geographical divisions of the 

 globe which may be submitted to his examination. The fauna 

 of each of these divisions presents a peculiar aspect, and may 

 be easily characterized by the presence of certain sj>. 

 more or less remarkable. 



631. Naturalists have imagined several hypothi - 

 explain this mode of distribution of animals on the surface of 

 the globe ; but in the actual state of science it is impossible 

 to give a satisfactory explanation, unless we admit that from 

 the beginning of the actual geological period the various 

 species have been distributed in the different regions, and that 

 by degrees they have afterwards spread to a distance, so as to 

 occupy a more or less considerable portion of the surface of 

 the globe. In the actual condition of the globe, it is impos- 

 sible for us to discover all the zoological focuses; for one mav 

 imagine the possibility of exchange so multiplied between 

 two regions, the fauna3 of which were primitively distinct, 

 that they can only now offer at the present moment species 

 common to both, and thus nothing can reveal to the eyes of 

 the naturalist their original separation ; but when a country 

 is found to be peopled with a considerable number of species 

 not to be found elsewhere, even where the local circumstances 

 most resemble, we shall be authorized to think that such a 

 portion of the globe has always been a distinct zoological 

 region. 



What the naturalist ought to inquire into is, not how it 

 happens that the various points of the globe are inhabited at 

 the present day by different species, but rather how these 

 animals have been able to spread themselves to a distance 

 over the surface of the globe, and how nature has set to this 

 diffusion variable limits, according to the species. This last 

 question especially presents itself to the mind, when we ob- 

 serve how unequal is the extent of the domain occupied by 

 different animals. The ourang-outang, for example, confined 

 to the Island of Borneo and the neighbouring territories ; the 



