120 ESSAY ON CLASSIFICATION 



behind the other divisions of that science. Nor should we wonder 

 at the fact that the geographical distribution of plants is so much 

 better known than that of animals, when we consider how marked a 

 feature the vegetable carpet which covers the surface of our globe is, 

 when compared with the little show animals make, almost every- 

 where. And yet it will perhaps some day be easier to understand the 

 relations existing between the geographical distribution of animals 

 and the other general relations prevailing among animals, because 

 the range of structural differences is much greater among animals 

 than among plants. Even now some curious coincidences may be 

 pointed out which go far to show that the geogTaphical distribution 

 of animals stands in direct relation to their relative standing in their 

 respective classes, and to the order of their succession in past geo- 

 logical ages, and more indirectly also to their embryonic growth. 

 Almost every class has its tropical families, and these stand gen- 

 erally highest in their respective classes; or, when the contrary is the 

 case, when they stand evidently upon a lower level, there is some 

 prominent relation between them and the prevailing types of past 

 ages. The class of Mammalia affords striking examples of these two 

 kinds of connection. In the first place, the Quadrumana, which, 

 next to Man, stand highest in their class, are all tropical animals; 

 and it is worthy of remark that the two highest types of Anthropoid 

 Monkeys, the Orangs of Asia and the Chimpanzees of Western 

 Africa bear in the coloration of their skin an additional similarity 

 to the races of Man inhabiting the same regions, the Orangs being 

 yellowish red, as the Malays, and the Chimpanzee blackish, as the 

 Negroes. The Pachyderms, on the contrary, stand low in their class, 

 though chiefly tropical; but they constitute a group of animals promi- 

 nent among the earliest representatives of that class in past ages. 

 Among Chiroptera the larger frugivorous representatives are essen- 

 tially tropical; the more omnivorous, on the contrary, occur every- 

 where. Among Carnivora, the largest, most powerful, and also highest 

 types, the Digitigrade, prevail in the tropics, while among the Planti- 

 grades, the most powerful, the Bears, belong to the temperate and 

 to the arctic zone, and the lowest, the Pinnate, are marine species of 

 the temperate and arctic seas. Among Ruminants we find the Giraffe 

 and the Camels in the warmer zones, the others everywhere. In the 



