74 Selection Docs Not Lead to Origin of Species. 



year. It shows us therefore the mean progress of the 

 yield. This hue comes closer every year to that of the 

 ears used for seed. A proper study of its course would 

 have necessitated the undertaking of effecting artificial 

 self-fertilization which in the case of maize is known 

 often to lead to a poor harvest. I should have preferred 

 to have used another plant, had not the ears of maize 

 lent themselves so admirably to a demonstration of this 

 kind. 



It is not necessary to repeat that the experience of 

 breeders provided the main support for Darwin's selec- 

 tion theory. In its broad outlines the process of natural 

 selection is like that of artificial selection. But as soon 

 as we come to dissect the component factors of these 

 processes we encounter serious difficulties, as I have al- 

 ready remarked in the Introduction. 



The chief cause of this state of affairs is to be sous^ht 

 in the circumstance that breeders rarely work with single 

 characters but have as a rule aimed at improving their 

 plants in every possible respect, 



They never attempt a separation, or even a separate 

 observation, of special characters. The second cause is 

 that breeders have no interest in distinguishing between 

 their different methods of improving their plants. On 

 the contrary it is usually the best plan to allow the various 

 methods : of the choice of desirable mutations, of their 

 gradual improvement by repeated selection, of natural 

 or artificial crossing, of manuring and what not, to exert 

 their combined effect. 



The breeder is only interested in the result. The 

 means by which this has been attained is a secondary 

 matter and is seldom thought worthy of an accurate 

 record. 



