Even now, some curious coincidences may be pointed out which go far to show that the geographical distribution of animals stands in direct relation to their rela- tive standing in their respective classes, and to the order of their succession in past geological ages, and more indirectly, also, to their embryonic growth.

Almost every class has its tropical families, and these stand generally 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 striliing 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 Cliimpanzees of Western Africa bear, in the coloration of their skin, an addi- tional 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 groujj of animals prominent among the earliest representatives of that class in past ages.