4.^8 CAUSES OF THE VARIETIES 



would be filled with maimed, imperfect, and monstrous 

 shapes." 



It is obvious that the external influences just considered, 

 even though we should allow to them a miuch greater influ- 

 ence on individuals than experience warrants us in admitting, 

 would be still entirely inadequate to account for those sig- 

 nal diversities, which constitute differences of race in ani- 

 mals. These can be explained only by two principles 

 already mentioned * ; namely, the occasional production of 

 an offspring with difterent characters from those of the pa- 

 rents, as a native or congenital variety ; and the propaga- 

 tion of such varieties by generation. It is impossible, in the 

 present state of physiological knowledge, to shew how this 

 is effected ; to explain why a gray rabbit or cat sometimes 

 brings forth at one birth^ and from one father, yellow, black, 

 white, and spotted young; why a white sheep sometimes 

 has a black lamb ; or why the same parents at different times 

 have leucaethiopic children, and others with the ordinary 

 formation and characters. 



The state of domestication, or the artificial mode of life, 

 which they lead under the influence of man, is the most power- 

 ful cause of varieties in the animal kingdom. Wild animals, 

 using always the same kind of food, being exposed to the action 

 of the climate without artificial protection, choose, each of 

 them, according to its nature, their zone and country. Instead 

 of migrating and extending, like man, they continue in those 

 places which are the most friendly to their constitutions. 

 Hence, their nature undergoes no change; their figure, co- 

 lour, size, proportions, and properties, are unaltered ; and, 

 consequently, there is no difficulty in determining their 

 species. Nothing can form a stronger contrast to this uni- 

 formity of specific character than the numerous and marked 

 varieties in those kinds which have been reduced by man. 

 To trace back our domestic animals to their wild originals 

 is in all cases difficult, in some impossible; long slavery has 

 so degraded their nature, that the primitive animal may be 



* See pp. 357 and following, ciSt and following. 



