r the result is thus soon made visible, and perseverance in
the work is encouraged. It can hardly be {236} accidental that the great
majority of the culinary and agricultural plants which have yielded
numerous races are annuals or biennials, which therefore are capable of
rapid propagation and thus of improvement. Sea-kale, asparagus, common and
Jerusalem artichokes, potatoes, and onions, alone are perennials. Onions
are propagated like annuals, and of the other plants just specified, none,
with the exception of the potato, have yielded more than one or two
varieties. No doubt fruit-trees, which cannot be propagated quickly by
seed, have yielded a host of varieties, though not permanent races; but
these, judging from pre-historic remains, were produced at a later and more
civilised epoch than the races of culinary and agricultural plants.

A species may be highly variable, but distinct races will not be formed, if
from any cause selection be not applied. The carp is highly variable, but
it would be extremely difficult to select slight variations in fishes
whilst living in their natural state, and distinct races have not been
formed;[580] on the other hand, a closely allied species, the gold-fish,
from being reared in glass or open vessels, and from having been carefully
attended to by the Chinese, has yielded many races. Neither the bee, which
has been semi-domesticated from an extremely remote period, nor the
cochineal insect, which was cultivated by the aboriginal Mexicans, has
yielded races; and it would be impossible to match the queen-bee with any
particular drone, and most difficult to match cochineal insects.
Silk-moths, on the other hand, have been subjected to rigorous selection,
and have produced a host of races. Cats, which from their nocturnal habits
cannot be selected for breeding, do not, as formerly remarked, yield
distinct races in the same country. The ass in England varies much in
colour and size; but it is an animal of little value, bred by poor people;
consequently there has been no selection, and distinct races have not been
formed. We must not attribute the inferiority of our asses to climate, for
in India they are of even smaller size than in Europe. But when selection
is brought to bear on the ass, all is changed. Near Cordova, as I am
informed (Feb. 1860) by Mr. W. E. Webb, C.E., they are carefully bred, as
much as 200l. having been paid for a stallion ass, {237} and they have been
immensely impro