be increased, civilization may be advanced in a 

 very direct and practical way. Before Darwin 

 the practices of animal and plant breeders were 

 largely empirical, based on unreasoned past ex- 

 perience, just as was in antiquity the practice 

 of metallurgy. Good plows and good swords 

 were made long before a scientific knowledge 

 of the metals was attained, but without that sci- 

 entific knowledge the wonderful industrial de- 

 velopment of this present age of steel would 

 have been quite impossible. In a similar way, 

 if not in like measure, we may reasonably hope 

 for an advance in the productiveness of animal 

 and plant breeding when the scientific principles 

 which underlie these basic arts are better under- 

 stood. Two practical problems present them- 

 selves to the breeder: (1) how to make best use 

 of existing breeds, and (2) how to create new 

 and improved breeds better adapted to the con- 

 ditions of present-day agriculture. We shall 

 concern ourselves with the second of these only. 

 The production of new and improved breeds 

 of animals and plants is historically a matter 

 about which we know scarcely more than about 



the production of new species in nature. Selec- 



3 



