Neo-Mendelism 8i 



JoHANNSEN, and others when they discovered what 

 they called elementary species or pure lines and demon- 

 strated that artificial selection could never result in any 

 large or permanent improvement. In consequence of 

 this, artificial selection, as the most important method 

 of securing desirable races, gave place to pedigree 

 culture at the most important experiment stations. It 

 was not abandoned, for it had its uses, but it seemed to 

 many to be a mediaeval method of breeding. The 

 artificial selection, however, which we have been de- 

 scribing is different from that so long practiced. In 

 brief statement the difference is as follows. 



In the first place, the selection proposed is preceded 

 by an intelligent hybridizing, and after that genotypes 

 rather than phenotypes are selected; that is, the selection 

 is made on the basis of germ plasm rather than of body 

 plasm. This would be a sufficient reason for the superi- 

 ority of the new method of artificial selection as com- 

 pared with the old. A little further analysis, however, 

 will make the difference clearer. 



In the old method of artificial selection the breeder, 

 in the first place, is dealing with such germinal variations 

 as happen to appear in his crop; and in the second place 

 he is dealing with those fluctuations which appear as 

 responses to the environment. When he selects a large 

 plant to use for seed that plant may be large on account 

 of its germinal constitution ; but on the other hand it may 

 be large because it is growing in a less crowded place 

 or is more heavily fertilized than the others. In that 

 case the large plant might not furnish good seed. The 

 plant breeder of the old method undoubtedly made such 

 unfortunate selections frequently; that is, he selected 



