72 PROBLEMS OF EVOLUTION 



together when goaded by hunger and devour a weak 

 fellow-rat. 



This principle of mutual help mitigates in a way the horrors 

 of the struggle for existence. But it does not in the least alter 

 the cardinal fact. The supply of food is limited, and those who 

 cannot by strength and courage or cunning get a share must 

 starve. Sometimes physical conditions may be the most formid- 

 able enemy, but in almost every case an animal has animal 

 enemies as well. Everywhere there is war from the polar 

 regions to the tropics, and in order to hold their own some 

 animals have found it best to combine. They fight in armies, 

 or in small companies instead of individually. This does a good 

 deal to ennoble the war, though it does not prevent it from 

 Love of being war. It has introduced in many species a love of society 

 lety without reference to the need of combined offensive or defen- 

 sive action. This must be the case unless we interpret the 

 conduct of sociable animals quite wrongly. Rooks must enjoy 

 each other's companionship when they fly round and round in 

 huge clanging flocks before they settle to roost. If gulls are 

 unsociable, why do a troop of them together practise their 

 evolutions in the air instead of each of them retiring to a 

 solitary place ? The fact is that characters that are stamped 

 on a species by Natural Selection because they are useful, 

 show themselves on occasions when nothing is to be gained 

 by them. Among social species the exercise of the social 

 instincts is one of the joys of life. All animals rise above a 

 mere business spirit. The horse delights in putting forth the 

 speed which he has gained to save him from his enemies. 

 Crises and If the struggle is really serious, how does it come about that 

 tervals P^ ants an( ^ animals have such a superabundance of vigour ? If 

 species, as a rule, can only just maintain their numbers, how is 

 it that the component individuals, when we happen to see them, 

 seem to have a superfluity of energy, seem not to feel the grip 

 of the ruthless system ? This is due to the fact that the struggle 

 comes only in crises. At such times the conditions of life are so 

 hard that only the strongest in each species are equal to the 

 strain, and even they have only a bare margin of superiority. 



