Hilaire has proved this in regard to size, and so it is with colour, and probably with the length of hair.

With respect to fleetness, which depends on many bodily characters, Eclipse was far fleeter, and a dray-horse is comparably stronger, than any two natural species belonging to the same genus.

So with plants, the seeds of the different varieties of the bean or maize probably differ more in size than do the seeds of the distinct species in any one genus in the same two families.

The same remark holds good in regard to the fruit of the several varieties of the plum, and still more strongly with the melon, as well as in many other analogous cases.

To sum up on the origin of our domestic races of animals and plants.