824 Fluctuations 



and much more reliable determination can be 

 made than on the ground of the minutest exam- 

 ination of one single plant. From this point of 

 view the method of Hays commands attention. 

 But the chief advantage lies in the fact that it is 

 a direct proof of that which it is desired to 

 prove, while the visible marks give only very in- 

 direct information. 



Thus the results of the men of practice are in 

 full accordance with those of theory and scien- 

 tific experiment, and there can be little doubt 

 that they open the way for a rapid and impor- 

 tant improvement. Once attained, progress 

 however, will be dependent on the selection- 

 principle, and the hereditary percentage, or 

 centgener power, or breeding-ability must be de- 

 termined in each generation anew. Without 

 this the race would soon regress to its former 

 condition. 



To return to our starting point, the compari- 

 son of artificial and natural selection. Here we 

 are at once struck by the fact that it is hardly 

 imaginable, how nature can make use of this 

 principle. In some measure the members of the 

 best centgener will manifestly be at an advan- 

 tage, because they contain more fit specimens 

 than the other groups. But the struggle for 

 existence goes on between individuals, and not 

 between groups of brethren against groups of 



