HEREDITY AND VARIATION 



253 



Charles Darwin and Natural Selection. - The great English- 

 man Charles Darwin was one of the first scientists to realize how 

 this great force of heredity applied to the development or evolu- 

 tion of plants and animals. He knew that although animals 

 and plants were like their ancestors, they also tended to vary. 

 In nature, the variations which best fitted a plant or animal for 

 life in its own environment were the ones which were handed 

 down because those having variations which were not fitted for 

 life in that particular environment would die. Thus nature 

 seized upon favorable variations and after a time, as the descend- 

 ants of each of these individuals also tended to vary, a new species 

 of plant or animal, fitted for the place it had to live in, would be 

 gradually evolved. 



Mutations. - - Recently a new method of variation has been 

 discovered by a Dutch naturalist, named Hugo de Vries. He 

 found that new species of plants and animals arise suddenly by 

 " mutations ' or steps. This means that new species instead of 

 arising from very slight variations, continuing during long periods 

 of years (as Darwin believed), might arise very suddenly as a very 

 great variation which would at once breed true. It is easily seen 

 that such a condition would be of immense value to breeders, as 

 new plants or animals quite unlike their parents might thus be 

 formed and perpetuated. It will be one of the future problems 

 of plant and animal breeders to isolate and breed * mutants," 

 as such organisms are 

 called. 



Artificial Selection. - 

 Darwin reasoned that 

 if nature seized upon 

 favorable variants, then 

 man by selecting the 

 variations he wanted, 

 could form new varie- 

 ties of plants or ani- 

 mals much more quickly 



than nature And SO Improvement in corn by selection. To the left, the 



corn improved by selection from the original 



to-day plant or animal type at the right. 



