Improved Races After Selection Ceases. 123 



opinion that selection must not be neglected even in a 

 single generation. Moreover whatever principle of se- 

 lection is adopted, must be adhered to throughout if any- 

 thing is to be attained. 



Only a few years are necessary for a complete retro- 

 gression. And no amount of selection can prevent this 

 retrogression or even diminish its influence. The breeder, 

 with infinite labor and patience, and working with a large 

 number of individuals, fixes his attention on, and im- 

 proves a certain set of characters. Then nature comes, 

 lays her hands on all the features of the race and elimi- 

 nates those which even in the slightest degree reduce the 

 strength of the plant. 



*'The more a race has been improved the less will it 

 bear a cessation of selection," says Von Rumker at the 

 end of his instructive discussion of this difficult problem.^ 

 Continued selection by no means fixes the character 

 chosen, but, by separating the race further from the 

 type from which it sprang, continually adds to the risk 

 of regression. The maintenance of an improvement 

 depends on the continuation of selection; for nature is 

 continually striving to reduce the new mean to the orig- 

 inal one. This mean is a state of equilibrium from 

 which skilful practice can only temporarily raise the char- 

 acters of a plant. 



There are certain experiments on the reversal of 

 selection which are worthy of our attention. 



Peas which have been cultivated for many years on 

 a warm dry soil regularly ripen their seeds in a short 

 time — often about forty days; but if they are sown in 

 another soil they preserve their property of early ripen- 



^ Von Rumker, Anleitung aur Cefreidcciichfnng. 1889, P- 8r. See 

 also LiNDLEY, Theory of Horticulture, 1840, p. 314. 



