170 
LAWS OF VAEIATION. 
Chap. V. 
tion, such modifications will add to the beautiful and 
harmonious diversity of nature. 
Whatever the cause may be of each slight difference 
in the offspring from their parents—and a cause for 
each must exist—it is the steady accumulation, through 
natural selection, of such differences, when beneficial to 
the individual, that gives rise to all the more important 
modifications of structure, by which the innumerable 
beings on the face of this earth are enabled to struggle 
with each other, and the best adapted to survive. 
