76 EVOLUTION AND NATUEAL THEOLOGY. 



become thoroughly domesticated, it will often 

 breed far more freely than in a wild state. Most 

 of our domestic animals have been handed 

 down to us domesticated, from a very early 

 period; and when first semi-domesticated by 

 savages would be almost under their natural 

 conditions, or at least would not suddenly be 

 exposed to such an amount of change of circum- 

 stances as to render them sterile in confinement. 

 This semi- domestication having been carried out 

 (as must have been the case) in a manner which 

 would not produce the ordinary primary effect 

 of domestication, viz., sterility, the secondary 

 and converse effect, viz., increased fertility, 

 would in time result. This would not im- 

 probably place originally distinct wild species in 

 a position towards each other resembling that 

 of races, rather than that of species ; for many 

 of our domestic animals (cattle, dogs, etc.) are 

 perfectly fertile when their most dissimilar 

 varieties are crossed, although they are believed 

 to be descended from several distinct wild 

 species. But if specific differences become 

 plastic under domestication, they can hardly be 

 regarded as absolute barriers between species 

 and species in a wild state. Practically, how- 



