use or habit. Our wonderfully-improved pigs
could never have been formed if they had been forced to search for their
own food; the English racehorse and greyhound could not have been improved
up to their present high standard of excellence without constant training.

As conspicuous deviations of structure occur rarely, the improvement of
each breed is generally the result, as already {235} remarked, of the
selection of slight individual differences. Hence the closest attention,
the sharpest powers of observation, and indomitable perseverance, are
indispensable. It is, also, highly important that many individuals of the
breed which is to be improved should be raised; for thus there will be a
better chance of the appearance of variations in the right direction, and
individuals varying in an unfavourable manner may be freely rejected or
destroyed. But that a large number of individuals should be raised, it is
necessary that the conditions of life should favour the propagation of the
species. Had the peacock been bred as easily as the fowl, we should
probably ere this have had many distinct races. We see the importance of a
large number of plants, from the fact of nursery gardeners almost always
beating amateurs in the exhibition of new varieties. In 1845 it was
estimated[575] that between 4000 and 5000 pelargoniums were annually raised
from seed in England, yet a decidedly improved variety is rarely obtained.
At Messrs. Carter's grounds, in Essex, where such flowers as the Lobelia,
Nemophila, Mignonette, &c., are grown by the acre for seed, "scarcely a
season passes without some new kinds being raised, or some improvement
affected on old kinds."[576] At Kew, as Mr. Beaton remarks, where many
seedlings of common plants are raised, "you see new forms of Laburnums,
Spiraeas, and other shrubs."[577] So with animals: Marshall,[578] in
speaking of the sheep in one part of Yorkshire, remarks, "as they belong to
poor people, and are mostly in small lots, they never can be improved."
Lord Rivers, when asked how he succeeded in always having first-rate
greyhounds, answered, "I breed many, and hang many." This, as another man
remarks, "was the secret of his success; and the same will be found in
exhibiting fowls,--successful competitors breed largely, and keep the
best."[579]

It follows from this that the capacity of breeding at an early age and at
short successive intervals, as with pigeons, rabbits, &c., facilitates
selection; fo