NILSSON'S DISCOVERY 93 



agricultural crops have been discovered as we have seen in our 

 preceding chapters. They are of a nature to turn over all 

 the old ideas concerning race-ameUoration and give proof 

 that the methods now generally in use in Europe are faulty 

 from a practical as well as from a scientific point of view. 

 The main discovery is that most of our ordinary agricultural 

 crops are composed not only of elementary species, as was 

 long known before, but that each cultural variety contains 

 hundreds of sharply definite types. These are widely dis- 

 tinct from one another in botanical characters as weh as in 

 those properties, which determine their utility from the 

 breeder's point of view, and thus they afford a rich material 

 for selection. 



For this chapter I have chosen an apphcation of these 

 discoveries of Nilsson to a criticism of the current views 

 concerning the bearing of agricultural breeding processes on 

 the theory of evolution. Formerly I urged my readers to 

 be careful not to trust too much to these processes and to 

 make use, in scientific discussions, of the most simple and 

 clear cases only (Mut. Theory I, p. 59). The new facts 

 now at hand go to prove that the apparently simple methods 

 of selection have been far more comphcated than their 

 authors suspected. The slow and gradual working up of a 

 cereal to a previously fixed ideal seemed to be a process of 

 the simplest possible nature. In reaUty, however, it is 

 composed of a series of factors which the breeders them- 

 selves have not recognized, and which therefore it is now 

 often impossible to discern in their descriptions. In gen- 

 eral such an analysis has been made practicable by Nilsson' s 

 discoveries. Unfortunately it leads to a less high apprecia- 

 tion of the merits of the breeders (Mut. Th., p. 82), but on 

 the other hand it gives a stronger support to the theory of 

 the saltatory origin of species. 



Among the results of the breeders' activity, two main 



