Artificial and Natural Sdection 807 



size and color are usually easy and rapid in the 

 beginning, but an impassable limit is soon 

 reached. Numerous other instances could be 

 given. 



Contrasted with these simple cases is the 

 method of selecting sugar-beets. More than 

 once I have alluded to this splendid exam- 

 ple of the influence of man upon domestic races, 

 and tried to point out how little support it af- 

 fords to the current scientific opinion concern- 

 ing the power of natural selection. For this 

 reason it is interesting to see how a gradual 

 development of the methods of selection has 

 been, from the very outset, one of the chief aims 

 of the breeders. None of them doubts that an 

 improvement of the method alone is adequate to 

 obtain results. This result, in the main, is the 

 securing of a few per-cent more of sugar, a 

 change hardly comparable with that progress 

 in evolution, which our theories are destined to 

 explain. 



Vilmorin's original method was a very sini])le 

 one. Polarization was still undiscovered in his 

 time. He determined the specific weight of his 

 beets, either by weighing them as a whole, or by 

 using a piece cut from the base of the roots and 

 deprived of its bark, in order to test only the 

 sugar-tissues. The pieces were floated in solu- 

 tions of salt, which were diluted until the pieces 



