74 BIOLOGY 



CHAPTER XIII 



THE STRUGGLE FOB EXISTENCE 



EVERY day forces upon our notice the fact that among 

 living organisms there is a continual struggle, a struggle 

 which may involve the victory or the total suppression 

 of some form of life. This is a struggle which is waged 

 alike in the animal and the vegetable kingdom, but 

 may be more easily understood if we consider it mainly 

 among the animals. 



Animals do not live alone, nor do they always pursue 

 the paths of peace. Wherever animals are found, there 

 also is there struggle ; a struggle which is older than 

 the fights of men, often very keen and often also to the 

 death, but which is often made of small importance by 

 the mutual aid and sympathy that exists among animals. 



If anyone doubts the reality of this struggle, let him 

 take a brief glance at the various forms of animals. 

 Throughout the whole there is a superabundance of 

 weapons and of armour. From the simplest forms with 

 their offensive threads we pass to the stings of insects, 

 the large pincers of crabs and lobsters, the teeth of 

 sharks, the horns and hoofs and fangs of mammals. 

 With armour it is just the same ; thus we have the shells 

 of crabs and molluscs, the scales of fishes and of reptiles, 

 and the hair and the feathers of mammals and birds. 



The forms of the struggle are very different. Hunger 



