Chap. I. UNDEE DOMESTICATION. 15 



single variety should be turned loose in its new home. 

 Nevertheless, as our varieties certainly do occasionally 

 revert in some of their characters to ancestral forms, it 

 seems to me not improbable, that if we could succeed in 

 naturalising, or were to cultivate, during many genera- 

 tions, the several races, for instance, of the cabbage, in 

 very poor soil (in which case, however, some effect would 

 have to be attributed to the direct action of the poor 

 soil), that they would to a large extent, or even wholly, 

 revert to the wild aboriginal stock. Whether or not the 

 experiment would succeed, is not of great importance 

 for our line of argument ; for by the experiment itself 

 the conditions of life are changed. If it could be shown 

 that our domestic varieties manifested a strong tendency 

 to reversion, — that is, to lose their acquired characters, 

 whilst kept under unchanged conditions, and whilst kept 

 in a considerable body, so that free intercrossing might 

 check, by blending together, any slight deviations of 

 structure, in such case, I grant that we could deduce 

 nothing from domestic varieties in regard to species. 

 But there is not a shadow of evidence in favour of this 

 view: to assert that we could not breed our cart and 

 race-horses, long and short-horned cattle, and poultry 

 of various breeds, and esculent vegetables, for an almost 

 infinite number of generations, would be opposed to all 

 experience. I may add, that when under nature the 

 conditions of life do change, variations and reversions 

 of character probably do occur ; but natural selection, 

 as will hereafter be explained, will determine how far 

 the new characters thus arising shall be preserved. 



When we look to the hereditary varieties or races of 

 our domestic animals and plants, and compare them with 

 species closely allied together, we generally perceive in 

 each domestic race, as already remarked, less uniformity 

 of character than in true species. Domestic races of 



