The Immutability of Domesticated Animals

It has often been assumed that man has chosen for domestication animals and plants having an extraordinary inherent tendency to vary. I do not dispute that these capacities have added largely to the value of most of our domesticated productions. In the case of strongly marked races or some other domesticated species, there is presumptive, or even strong evidence, that all are descended from a single wild stock. For instance, of the many foxes inhabiting the different quarters of the world, i do not believe as we shall presently see that the whole amount of difference between the several breeds of the dog has been produced under domestication.