VARIATION UNDER DOMESTICATION. 13 



of course confined to the first appearance of the peculiarity, 

 and not to the primary cause which may have acted on the 

 ovules or on the male element; in nearly the same manner 

 as the increased length of the horns in the offspring fron 

 a short-horned cow by a long-horned bull, though appear^ 

 ing late in life, is clearly due to the male element. 



Having alluded to the subject of reversion, I may here 

 refer to a statement often made by naturalists — namely, 

 that our domestic varieties, when run wild, gradually but 

 invariably revert in character to their aboriginal stocks. 

 Hence it has been argued that no deductions can be drawn 

 from domestic races to species in a state of nature. I have 

 in vain endeavored to discover on what decisive facts 

 the above statement has so often and so boldly been made. 

 There would be great difficulty-in proving its truth: we 

 may safely 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 per- 

 fect reversion had ensued. It would be necessary, in order 

 to prevent the effects of intercrossing, that only a single 

 variety should have been 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 

 naturalizing, or were to cultivate, during many gener- 

 ations, 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 definite 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, while 

 kept under the same conditions and while kept in a con- 

 siderable body, so that free intercrossing might check, by 

 blending together, any slight deviations 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 favor of this view: to assert that we 



