THE STRUGGLE FOR EXISTENCE 75 



and love may be said to lie at the base of all. Food 

 has to be found for all, and which mouth is to be fed 

 has to be decided often by tooth and claw. Many 

 animals are carnivorous and must feed on others, which 

 do all they can to prevent a horrible death. In other 

 cases the struggle may be for mates, sometimes a peace- 

 ful struggle, but often one to the bitter end. There is 

 another kind of struggle, the struggle between an animal 

 and its environment. 



That there is a struggle between living organisms 

 we cannot deny. Fellows strive for their share of 

 food; between foes there is a constant attack and 

 counter-attack ; mates have to be won and many are 

 disappointed ; and over all is a changeful physical 

 environment which, as we shall see, has no mercy. But 

 throughout it all, ennobling it and raising it high above 

 the petty strivings of mankind, we recognise the presence 

 of altruism, parental love and sacrifice, mutual aid and 

 care for others. 



Before we consider these different forms of struggle, 

 we must call attention to the enormous powers of 

 increase possessed by organisms if considered as living 

 under favourable conditions. 



A single purslane may give rise to two million seeds, 

 a single infusorian may be the ancestor of millions at 

 the end of a week, and were all the eggs of every cod- 

 fish, ten millions for each, to reach maturity the whole 

 sea would immediately become crowded with cod-fish. 



But fortunately these multiplications rarely occur, 

 and we have to thank the struggle in nature, especially 

 the struggle against environment, that they do not. 





