THE ISSUES OF LIFE 299 



]S T ow the story which had till recently all the expert 

 authority behind it, is that the larger, stronger, fiercer Brown 

 Rat killed off the Black Rat everywhere, and by competition 

 to the death took its place. But the account of the matter 

 given by Dr. Chalmers Mitchell is very different. The Black 

 Rat is far from being extinct in Britain ; it is wild and shy, 

 much more active than the Brown Rat; it is the typical 

 barn and granary rat. The Brown Rat is more of an out- 

 door creature, though the haunter of sewers and drains, to 

 the great extension of which it probably owes a considerable 

 part of its success. 



Let us allow that the ranks of the Black Rat have been 

 increased by fresh imports; let us allow that it once was 

 the ' common rat ' and is so no longer ; let us even allow 

 that if representatives of the two species are shut up in a 

 cage together (a condition of which there are few counter- 

 parts in nature!) the brown rats will kill the blacks; yet 

 the edge has been taken off Darwin's famous illustration, 

 the best piece of evidence he adduced in support of his thesis. 

 As Dr. Chalmers Mitchell says, " In this story of the rats, 

 which has been very carefully investigated, there is no trace 

 of a process comparable with the German theory of war 

 as an instance of the struggle for existence. . . . Each 

 species has its different aptitudes, capacities, and prefer- 

 ences, and each insinuates itself into the most suitable en- 

 vironment " (1915, p. 30). The internecine competition 

 has not taken place. A compromise was effected. 



The second form of the struggle for existence is between 

 animate foes of entirely different kinds, between herbivore 

 and carnivore, between birds of prey and small mammals, 

 between the grass and the other plants of the meadow, be- 

 tween the thorns and the seedlings in the stony ground. 



