NILSSON'S DISCOVERY 47 



they thought it possible to give them. Starting from this 

 point of view, it was essential not to begin with one single 

 mother plant, for this might perhaps possess, among those 

 qualities which necessarily or at least ordinarily escape obser- 

 vation, some inferior ones, which, it must be feared, might 

 destroy the whole effect of the ameliorations obtained on 

 other points. Dependence on soil and manure, resistance 

 to disease and other essential qualities are not so easily taken 

 into consideration when the selection is performed only at the 

 time of the harvest, as was then the custom. In order to 

 become as independent of these as possible, the only way 

 seemed to start with quite a considerable number of indi- 

 viduals and to rely on the laws of chance, trusting that these 

 would keep all qualities in their average state, except those 

 which should be consciously subjected to selection. It 

 was this group of individuals that was to be ameliorated. 

 A scheme of the desired improvements was made, and" each 

 year those ears or panicles were selected which more fully 

 complied with it than the remainder. The result was a 

 slow progress, but it was thought to be more reliable than the 

 sudden amelioration of the English breeders. Moreover, 

 sudden improvements are, as a matter of fact, limited in 

 their degree, and even the pedigree- cultures of Hallett did 

 not escape from this objection. The German principle 

 was assumed to be unlimited, progress along the prescribed 

 lines seeming to be always possible. 



As pointed out in the beginning, Darwin has, in large 

 part, founded his theory of the slow and gradual change 

 by which the species of plants and animals are transformed 

 into one another, on the views of the German breeders of 

 his time. For this reason we shall have to subject their 

 principles to an elaborate criticism and the short indication 

 given may therefore be sufficient for our present purpose. 



The most general conclusion to which our historical 



