126 Selection Does Not Lead to Origin of Species. 



rows. In three years therefore the effect of the pre- 

 vious selection had disappeared. 



The Progeny of the Original Seed. It is this retro- 

 gression which attends the cessation of selection which 

 is, as we have already said, the chief difference between 

 highly improved agricultural races and the so-called vari- 

 eties or subspecies. The rational farmer buys his seed 

 from that source in which it has been brought to the 

 highest pitch of productiveness, whether this has happened 

 by empirical or methodical selection or by particularly 

 favorable conditions of climate and soil which act as a 

 kind of natural selection. Such stock seed is of course 

 dear. In the case of cereals and particularly in the case 

 of flax, the custom is therefore to sow the bought seed 

 and to use the harvest thus raised for the main crop ; 

 some of which may again be used for seed.^ But the 

 race does not retain its good qualities longer than two 

 generations ; and in order to have a satisfactory harvest 

 it is necessary to replenish the stock seed from time to 

 time. 



We see therefore that original seed and its progeny 

 can be wholly different in their yield. ^ And the differ- 

 ence is great in proportion as the conditions of cultiva- 

 tion are dissimilar and in proportion to the number of 

 generations grown from the same lot of bought seed. 

 In the first year the race retains its good qualities, but 

 as soon as the conditions of life become different or the 

 care spent in choosing seed for next year becomes less 

 than that exercised previously, the good qualities of the 

 race begin to disappear. 



Change of Seed is a practice largely carried on in 



^ Langethal, Landzvirthschaftlichc PHanzenkunde. 



^VoN RiJMKER, Der zvirthschaftliche Mehrwerth, loc. cit., p. 136. 



