tio Kelleia was not the progenitor of a race of six-fingered men, as
Seth Wright's ram became a nation of Ancon sheep, though the tendency of
the variety to perpetuate itself appears to have been fully as strong,
in the one case as in the other. And the reason of the difference is not
far to seek. Seth Wright took care not to weaken the Ancon blood by
matching his Ancon ewes with any but males of the same variety, while
Gratio Kelleia's sons were too far removed from the patriarchal times to
intermarry with their sisters; and his grandchildren seem not to have
been attracted by their six-fingered cousins. In other words, in the one
example a race was produced, because, for several generations, care was
taken to _select_ both parents of the breeding stock, from animals
exhibiting a tendency to vary in the same direction; while, in the
other, no race was evolved, because no such selection was exercised. A
race is a propagated variety; and as, by the laws of reproduction,
offspring tend to assume the parental form, they will be more likely to
propagate a variation exhibited by both parents than that possessed by
only one.

There is no organ of the body of an animal which may not, and does not,
occasionally, vary more or less from the normal type; and there is no
variation which may not be transmitted, and which, if selectively
transmitted, may not become the foundation of a race. This great truth,
sometimes forgotten by philosophers, has long been familiar to practical
agriculturists and breeders: and upon it rest all the methods of
improving the breeds of domestic animals, which, for the last century,
have been followed with so much success in England. Colour, form, size,
texture of hair or wool, proportions of various parts, strength or
weakness of constitution, tendency to fatten or to remain lean, to give
much or little milk, speed, strength, temper, intelligence, special
instincts; there is not one of these characters whose transmission is
not an every-day occurrence within the experience of cattle-breeders,
stock-farmers, horse-dealers, and dog and poultry fanciers. Nay, it is
only the other day that an eminent physiologist, Dr. Brown-Sequard,
communicated to the Royal Society his discovery that epilepsy,
artificially produced in guinea-pigs, by a means which he has
discovered, is transmitted to their offspring.

But a race, once produced, is no more a fixed and immutable entity than
the stock whence it sprang; vari