ow been
exported to almost every quarter of the world. The improvement is by no
means generally due to crossing different breeds; all the best breeders
are strongly opposed to this practice, except sometimes amongst closely
allied sub-breeds. And when a cross has been made, the closest selection
is far more indispensable even than in ordinary cases. If selection
consisted merely in separating some very distinct variety, and breeding
from it, the principle would be so obvious as hardly to be worth
notice; but its importance consists in the great effect produced by
the accumulation in one direction, during successive generations, of
differences absolutely inappreciable by an uneducated eye--differences
which I for one have vainly attempted to appreciate. Not one man in
a thousand has accuracy of eye and judgment sufficient to become an
eminent breeder. If gifted with these qualities, and he studies his
subject for years, and devotes his lifetime to it with indomitable
perseverance, he will succeed, and may make great improvements; if he
wants any of these qualities, he will assuredly fail. Few would readily
believe in the natural capacity and years of practice requisite to
become even a skilful pigeon-fancier.

The same principles are followed by horticulturists; but the variations
are here often more abrupt. No one supposes that our choicest
productions have been produced by a single variation from the aboriginal
stock. We have proofs that this is not so in some cases, in which exact
records have been kept; thus, to give a very trifling instance, the
steadily-increasing size of the common gooseberry may be quoted. We see
an astonishing improvement in many florists' flowers, when the flowers
of the present day are compared with drawings made only twenty or thirty
years ago. When a race of plants is once pretty well established, the
seed-raisers do not pick out the best plants, but merely go over their
seed-beds, and pull up the "rogues," as they call the plants that
deviate from the proper standard. With animals this kind of selection
is, in fact, also followed; for hardly any one is so careless as to
allow his worst animals to breed.

In regard to plants, there is another means of observing the accumulated
effects of selection--namely, by comparing the diversity of flowers in
the different varieties of the same species in the flower-garden; the
diversity of leaves, pods, or tubers, or whatever part is valued, in the
ki