Chap. XXYIII. CONCLUDING EEMAEKS. 401 



countries has not prevented their domestication. Still less 

 could man have foreseen whether his animals and plants 

 would vary in succeeding generations and thus give birth to 

 new races ; and the small capacity of variability in the goose 

 has not prevented its domestication from a remote epoch. 



With extremely few exceptions, all animals and plants 

 which have been long domesticated have varied greatly. It 

 matters not under what climate, or for what purpose they are 

 kept, whether as food for man or beast, for draught or hunt- 

 ing, for clothing or mere pleasure, — under all these circum- 

 stances races have been produced which differ more from one 

 another than do the forms which in a state of nature are 

 ranked as different species. Why certain animals and plants 

 have varied more under domestication than others we do not 

 know, any more than why some are rendered more sterile 

 than others under changed conditions of life. But we have 

 to judge of the amount of variation which our domestic pro- 

 ductions have undergone, chiefly by the number and amount 

 of difference between the races which have been formed, and 

 we can often clearly see why many and distinct races have 

 not been formed, namely, because slight successive variations 

 have not been steadily accumulated ; and such variations will 

 never be accumulated if an animal or plant be not closely 

 observed, much valued, and kept in large numbers. 



The fluctuating, and, as far as we can judge, never-ending 

 variability of our domesticated productions, — the plasticity of 

 almost their whole organisation, — is one of the most important 

 lessons which we learn from the numerous details given in 

 the earlier chapters of this work. Yet domesticated 'animals 

 and plants can hardly have been exposed to greater changes 

 in their conditions of life than have many natural species 

 during the incessant geological, geographical, and climatal 

 changes to which the world has been subject; but domes- 

 ticated productions will often have been exposed to more 

 sudden changes and to less continuously uniform conditions. 

 As man has domesticated so many animals and plants be- 

 longing to widely different classes, and as he certainly did not 

 choose with prophetic instinct those species which would va^ 

 most, we may infer that all natural species, if exposed to 



