39 



e. The Inheritance of Variations. 



The force of heredity. 



Capriciousness of heredity. 



(See above VI. 6, iii.) 



Racial variations arise from the inheritance of 

 individual variations. 



ii. The Struggle for Existence. 



(Benjamin Franklin, Observations concerning the Increase of 

 Mankind, Collected Works, Vol. 2, p. 231 ; Malthus, Essay 

 on the Principle of Population, 1803 ; Darwin, Origin of 

 Species, Chap. Ill; Wallace, Darwinism, pp. 14-40; Hud- 

 son, The Naturalist in La Plata, pp. 59-68 ; Brehm, From 

 North Pole to Equator; Romanes, Darwin and after Darwin, 

 Vol. I, pp. 259-270.) 



The apparent peace in nature. 



Species on the average contain a constant number of 

 individuals. 



This in spite of the tendency to increase in geometri- 

 cal ratio. 



Examples — The elephant. 



Man. 



The carrion fly. 



The common birds. 

 Effect of introduction into a free field. 

 Our common weeds. 

 The English sparrow in our country. 

 The horses and cattle of the plains. 

 Rabbits in New Zealand. 

 Hogs in Central America. 

 The tendency of plants to increase. 

 The great number of seeds produced. 



