reat 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; variations arise among its members, and
as these variations are transmitted like any others, new races may be
developed out of the pre-existing one ad infinitum, or, at least, within
any limit at present determined. Given sufficient time and sufficiently
careful selection, and the multitude of races which may arise from a
common stock is as astonishing as are the extreme structural differences
which they may present. A remarkable example of this is to be found in
the rock-pigeon, which Dr. Darwin has, in our opinion, satisfactorily
demonstrated to be the progenitor of all our domestic pigeons, of which
there are certainly more than a hundred well-marked races. The most
noteworthy of these races are, the four great stocks known to the
"fancy" as tumblers, pouters, carriers, and fantails; birds which not
only differ most singularly in size, colour, and habits, but in the
form of the beak and of the skull: in the proportions of the beak to the
skull; in the number of tail-feathers; in the absolute and relative size
of the feet; in the presence or absence of the uropygial gland; in the
number of vertebrae in the back; in short, in precisely those characters
in which the genera and species of birds differ from one another.

And it is most remarkable and instructive to observe, that none of these
races can be shown to have been originated by the action of changes
in what are commonly called ex