4492 THE CAUSES OF THE XI 
already said, the operation of nature is exactly 
the same as the artificial operation of man. 
But if this be true of that simple case, which I 
put before you, where there is nothing but the 
rivalry of one member of a species with others, 
what must be the operation of selective conditions, 
when you recollect as a matter of fact, that for 
every species of animal or plant there are fifty or 
a hundred species which might all, more or less, be 
comprehended in the same climate, food, and sta- 
tion ;—that every plant has multitudinous animals 
which prey upon it, and which are its direct oppo- 
nents ; and that these have other animals preying 
upon them,—that every plant has its indirect 
helpers in the birds that scatter abroad its seed, 
and the animals that manure it with their dung ;— 
I say, when these things are considered, it seems 
impossible that any variation which may arise in 
a species in nature should not tend in some way 
or other either to'be a little better or worse than 
the previous stock ; if it is a little better it will 
have an advantage over and tend to extirpate the | 
latter in this crush and struggle; and if it is a 
little worse it will itself be extirpated. 
I know nothing that more appropriately ex- 
presses this, than the phrase, “the struggle for 
existence”; because it brings before your minds, 
in a vivid sort of way, some of the simplest pos- 
sible circumstances connected with it. When a 
struggle is intense there must be some who are 
