CHAPTER XI.

WE have pointed out in the preceding chapters the strict dependence of each 
species of animal and plant on certain physical conditions in the state of the 
earth's surface, and on the number and attributes of other organic beings 
inhabiting the same region. We have also endeavoured to show that all these 
conditions are in a state of continual fluctuation, the igneous and aqueous 
agents remodelling, from time to time, the physical geography of the globe, and 
the migrations of species causing new relations to spring up successively 
between different organic beings. We have deduced as a corollary, that the 
species existing at any particular period must, in the course of ages, become 
extinct one after the other. “They must die out,” to borrow an emphatical 
expression from Buffon, “because Time fights against them.”
 

If the views which we have taken are just, there will be no difficulty in 
explaining why the habitations of so many species are now restrained within 
exceedingly narrow limits. Every local revolution, such as those contemplated in 
the preceding chapter, tends to circumscribe the range of some species, while it 
enlarges that of others ; and as we have been led to infer that new species 
originate in one spot only, each must require tinge to diffuse itself over a 
wide area. The recent origin,