14 ON THE ORIGIN OF SPECIES 



conclude that very many of the most strongly-marked 

 domestic varieties could not possibly live in a wild 

 state. In many cases we do not know what the 

 aboriginal stock was, and so could not tell whether or 

 not nearly perfect reversion had ensued. It would be 

 quite necessary, in order to prevent the effects of inter- 

 crossing, that only a 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 generations, 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 experi- 

 ment 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 char- 

 acters, whilst kept under the same conditions, and whilst 

 kept in a considerable body, so that free intercrossing 

 might check, by blending together, any slight devia- 

 tions in their 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, varia- 

 tions 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 



