38 ON THE TENDENCY OF VARIETIES TO DEPART 



on a limited scale, yet, if applied to high numbers, 

 the results come nearer to what theory demands, 

 and, as we approach to an infinity of examples, 

 become strictly accurate. Now the scale on which 

 nature works is so vast the numbers of individuals 

 and the periods of time with which she deals ap- 

 proach so near to infinity, than any cause, how- 

 ever slight, and however liable to be veiled and 

 counteracted by accidental circumstances, must in 

 the end produce its full legitimate results. 



The Partial Reversion of Domesticated Varieties 

 explained. 



Let us now turn to domesticated animals, and in- 

 quire how varieties produced among them are affected 

 by the principles here enunciated. The essential 

 difference in the condition of wild and domestic 

 animals is this, that among the former, their well- 

 being and very existence depend upon the full exer- 

 cise and healthy condition of all their senses and 

 physical powers, whereas, among the latter, these are 

 only partially exercised, and in some cases are abso- 

 lutely unused. A wild animal has to search, and 

 often to labour, for every mouthful of food to ex- 

 ercise sight, hearing, and smell in seeking it, and 

 in avoiding dangers, in procuring shelter from the 

 inclemency of the seasons, and in providing for the 

 subsistence and safety of its offspring. There is no 

 muscle of its body that is not called into daily and 

 hourly activity; there is no sense or faculty that is 



