442 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 iu 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 



