38 The Study of Animal Life part i 



Before we consider these different forms of struggle, let 

 us notice the rapid multiplication of individuals which 

 furnishes the material for what in " a wide and meta- 

 phorical sense " may be called a " battlefield." 



A single Infusorian may be the ancestor of millions by 

 the end of a week. A female aphis, often producing one 

 offspring per hour for days together, might in a season be 

 the ancestor of a progeny of atomies which would weigh 

 down five hundred millions of stout men. " The roe of a 

 cod contains sometimes nearly ten million eggs, and sup- 

 posing each of these produced a young fish which arrived 

 at maturity, the whole sea would immediately become a 

 solid mass of closely packed codfish." The unchecked 

 multiplication of a few mice or rabbits would soon leave no 

 standing-room on earth. 



But fortunately, with the exception of the Infusorians, these 

 multiplications do not occur. We have to thank the 

 struggle in nature, and especially the physical environment, 

 that they do not. The fable of Mirza's bridge is continually 

 true, — few get across. 



(a) It is often said that the struggle between fellows of the 

 same kind and with the same needs is keenest of all, but 

 this is rather an assumption than an induction from facts. 

 The widespread opinion is partly due to an a priori con- 

 sideration of the problem, partly to that anthropomorphism 

 which so easily besets us. We transfer to the animal 

 world our own experience of keen competition with fellows 

 of the same caste, and in so doing are probably unjust. 

 Thus Mr. Grant Allen says — 



" The baker does not fear the competition of the butcher in the 

 struggle for life j it is the competition of the other bakers that 

 sometimes inexorably crushes him out of existence. ... In this 

 way the great enemies of the individual herbivores are not the 

 carnivores, but the other herbivores. ... It is not so much the 

 battle between the tiger and the antelope, between the wolf and 

 the bison, between the snake and the bird, that ultimately results 

 in natural selection or survival of the fittest, as the struggle between 

 tiger and tiger, between bison and bison, between snake and snake, 

 between antelope and antelope. '. . . Homo homini lupus, says 

 the old proverb, and so, we may add, in a wider sense, lupus lupo 



