Chap. L] VARIATION UNDER DOMESTICATION. 1 1 



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 from a short-homed cow hy a long-horned bull, though 

 appearing 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 charac- 

 ter 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 endeavoured 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 varie- 

 ties 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 necessary, 

 in order to prevent the effects of intercrossing, that only a single 

 variety should have been turned loose in its new home. Neverthe- 

 less, 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 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, whilst kept 

 under the same conditions, and whilst kept in a considerable 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 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 unlimited number of generations, would be 

 opposed to all experience. 



