CHAPTER I.

IN our first volume we treated of the changes which have taken place in the 
inorganic world within the historical era, and we must next turn our attention 
to those now in progress in the animate creation. In examining this class of 
phenomena, we shall treat first of the vicissitudes to which species are 
subject, and afterwards consider the influence of the powers of vitality in 
modifying the surface of the earth and the material constituents of its crust.
 

The first of these divisions will lead us, among other topics, to inquire, 
first, whether species have a real and permanent existence in nature ; or 
whether they are capable, as some naturalists pretend, of being indefinitely 
modified in the course of a long series of generations ? Secondly, whether, if 
species have a real existence, the individuals composing them have been derived 
originally from many similar stocks, or each from one only, the descendants of 
which have spread themselves gradually from a particular point over the 
habitable lands and waters ? Third, how far the duration of each species of 
animal and plant is limited by its dependance on certain fluctuating and 
temporary conditions in the state of the animate and inanimate