546 ZOOLOGY. 



spoken, that is to say, of the actual condition of the geo- 

 graphic distribution of animated beings. When we compare 

 the various regions of the globe with each other in the rela- 

 tion of their zoological population, one is struck at first with 

 the extreme inequality observable in the number of species. 

 In a certain country, for example, we meet with an extreme 

 diversity in the forms and the structure of the animals com- 

 posing its fauna, whilst elsewhere there reigns in this respect 

 a great uniformity ; and it is easy to observe a certain relation 

 between the different degrees of zoological richness and the 

 elevation, more or less considerable, of the temperature. In 

 fact, the number of species, as well marine as terrestrial, aug- 

 ments in general in proportion as we descend from the poles 

 towards the equator. The more remote polar regions offer to 

 the traveller only a few insects, and in its icy seas the fishes 

 and the mollusca themselves are but little varied ; in tem- 

 perate climates the fauna becomes more numerous in species ; 

 but it is in the tropical regions that nature shows herself 

 most prodigal in this respect, and the zoologist cannot see 

 without astonishment the endless diversity of animals which 

 are accumulated there. 



It is remarkable also that there exists a singular coin- 

 cidence between the elevation of the temperature in different 

 zoological regions, and the degree of organic perfection of the 

 animals inhabiting them. It is in the hottest climates that 

 we find the animals which mosfc approach man, and those 

 which in each great zoological division possess the orga- 

 nization the most complex, and the faculties most developed ; 

 whilst in the polar regions we meet only with beings occupy- 

 ing a rank but little elevated in the zoological series. The 

 apes, for example, are limited to the hottest parts of the two 

 continents; it is the same with the -parrots amongst birds; 

 the crocodiles, the turtles, and tortoises amongst reptiles, and 

 land- crabs amongst the Crustacea, all animals the most 

 perfect in their respective classes. 



It is also in hot countries that we find the terrestrial the 

 most remarkable for the beauty of their colours, the size of 

 their bodies, and the singularity of their forms. 



Finally, there seems to exist a certain relation between the 

 climate and the tendency of nature to produce such or such 

 an animal form. Thus we observe a great resemblance be- 

 tween most of the animals inhabiting the Boreal and Austral 

 regions ; the faunae of the temperate regions of Europe, Asia, 



