in THE STRUGGLE OF LIFE 43 



in one locality, divide into two parties and migrate up 

 and down stream. The old proverb which Grant Allen 

 quotes, Homo homini lupus, is surely a self-contradictory 

 libel ; the extension of the libel to the animal world has 

 certainly not been justified by careful induction. The 

 big fact, we repeat, is this, that animals react against 

 difficulties sometimes by increased intensity of competi- 

 tion, and sometimes by increased co-operation and 

 sociality, and that both solutions have been justified 

 in the past and are justified still. See Kropotkin, 

 Mutual Aid, and Cresson's L'Espece et son Serviteur. 



(b) Of the struggle between foes differing widely in 

 kind little need be said. It is very apparent, especially 

 in wild countries. Carnivores prey upon herbivores, 

 which sometimes unite in successful resistance. Birds of 

 prey devour small mammals, and sometimes have to fight 

 hard for their booty. Reptiles also have their battles 

 witness the combats between snake and mongoose. In 

 many cases, however, carnivorous animals depend upon 

 small fry ; thus many birds feed on fishes, insects, and 

 worms, and many fishes live on minute crustaceans. 

 Where the victims are unable to make any protective 

 reaction at all, there is no struggle. Where certain 

 members of the species give a more effective response 

 than others, they succeed, but they do not succeed by war- 

 ring against their kin. When one of our worst enemies 



-a plague-germ enters a household and kills half of the 

 members, the survivors do not succeed in competition 

 with their brothers and sisters, they succeed because they 

 had constitutions able to parry the microbe. 



(c) In a great number of cases there is between rival 

 males a contest for the possession of the females, a 

 competition in which beauty and winsomeness are some- 

 times as important as strength. Contrast the musical 

 competition between rival songsters with the fierce com- 

 bats of the stags. Many animals are not monogamous, 

 and this causes strife ; a male seal, for instance, guards 

 his harem with ferocitv. 



V 



(d) Finally, physical nature is quite careless of life. 

 Changes of medium, temperature, and moisture con- 



