258 THE HISTORY OF CREATION. 
actively or passively. Every animal and every plant 
struggles directly with a number of enemies, beasts of prey, 
parasitic animals, etc. Plants standing together struggle 
with one another for the space of ground requisite for their 
roots, for the necessary amount of light, air, moisture, etc. 
In like-manner, animals living together struggle with one 
another for their food, dwelling-place, ete. In this most 
active and complicated struggle, any personal superiority, 
however small, any individual advantage, may possibly 
decide the issue in favour of the one possessing it. This 
privileged individual remains the victor in the struggle, and 
propagates itself, while its fellow-competitors perish before 
they succeed in propagating themselves. The personal ad- 
vantage which gave it the victory is transmitted by inherit- 
ance to its descendants, and by a further development may 
become so strongly marked as to cause us to consider the 
later generations as a new species. 
The infinitely complicated correlations which exist be- 
tween the organisms of every district, and which must be 
looked upon as the real conditions of the struggle for 
life, are mostly unknown to us, and are very difficult 
to discover. We have hitherto been able to.trace them 
only to a certain point in individual cases, as in the 
example given by Darwin of the relations between cats and 
red clover in England. The red clover (Trifolium pratense), 
which in England is among the best fodder for cattle, 
requires the visit of humming-bees in order to attain the 
formation of seeds. These insects, while sucking the honey 
from the bottom of the flower, bring the pollen in contact 
with the stigma, and thus cause the fructification of the 
flower, which never takes place without it. Darwin has 
