EXCURSIONS OF AN EVOLUTIONIST 



Such broad facts as the successive appearance 

 of various sloth-like and armadillo-like animals 

 in South America, or of various marsupials and 

 monotremes in Australia, forcibly suggest the 

 descent of the later forms from the earlier ones 

 that lived in the same countries. Of like im- 

 port is the general fact that in the course of 

 geological succession any given organism is sure 

 to be intermediate in character between those 

 that have preceded and those that have followed 

 it. But still more powerfully suggestive even 

 than this is the fact that, in proportion as we go 

 back in geologic time, we find the characteris- 

 tics of plants and animals to be less and less 

 distinctly specialized : so that, for example, in 

 the Eocene period, instead of horses and tapirs 

 such as now exist we flnd an animal something 

 like a tapir and something like a horse; and 

 instead of leopards and wolves and bears we 

 find carnivorous animals, not specialized as of 

 feline or canine or ursine family, but with some 

 points of resemblance to all three, and with 

 some points like opossums and wombats into 

 the bargain. In conformity with this general 

 principle, the arrangement of organisms accord- 

 ing to their succession in geologic time would 

 be like the branches and branchlets of a tree, 

 which is the typical form of arrangement where 

 the link that connects the facts arranged is the 

 link of parentage. 



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