482 
CONCLUSION. 
Chap. XIV. 
lines of inland cliffs had been formed, and great valleys 
excavated, by the slow action of the coast-waves. The 
mind cannot possibly grasp the full meaning of the 
term of a hundred million years; it cannot add up 
and perceive the full effects of many slight variations, 
accumulated during an almost infinite number of ge¬ 
nerations. 
Although I am fully convinced of the truth of the 
views given in tliis volume under the form of an 
abstract, I by no means expect to convince experienced 
naturalists whose minds are stocked with a multitude 
of facts all viewed, during a long course of years, from 
a point of view directly opposite to mine. It is so easy 
to hide our ignorance under such expressions as the 
plan of creation,” unity of design,” &c., and to think 
that we give an explanation when we only restate a fact. 
Any one whose disposition leads him to attach more 
weight to unexplained difSculties than to the explana¬ 
tion of a certain number of facts will certainly reject 
my theory. A few naturalists, endowed with much 
flexibility of mind, and who have already begun to 
doubt on the immutability of species, may be influenced 
by this volume ; but I look with confidence to the future, 
to young and rising naturalists, who will be able to 
view both sides of the question with impartiality. Who¬ 
ever is led to believe that species are mutable will do 
good service by conscientiously expressing his convic¬ 
tion ; for only thus can the load of prejudice by which 
this subject is overwhelmed be removed. 
Several eminent naturalists have of late published 
their belief that a multitude of reputed species in each 
genus are not real species; but that other species are 
real, that is, have been independently created. This 
seems to me a strange conclusion to arrive at. They 
admit that a multitude of forms, which till lately 
