A high degree of variability is
obviously favourable, as freely giving the materials for selection to
work on; not that mere individual differences are not amply
sufficient, with extreme care, to allow of the accumulation of a large
amount of modification in almost any desired direction. But as
variations manifestly useful or pleasing to man appear only
occasionally, the chance of their appearance will be much increased by
a large number of individuals being kept; and hence this comes to be
of the highest importance to success. On this principle Marshall has
remarked, with respect to the sheep of parts of Yorkshire, that "as
they generally belong to poor people, and are mostly IN SMALL LOTS,
they never can be improved." On the other hand, nurserymen, from
raising large stocks of the same plants, are generally far more
successful than amateurs in getting new and valuable varieties. The
keeping of a large number of individuals of a species in any country
requires that the species should be placed under favourable conditions
of life, so as to breed freely in that country. When the individuals
of any species are scanty, all the individuals, whatever their quality
may be, will generally be allowed to breed, and this will effectually
prevent selection. But probably the most important point of all, is,
that the animal or plant should be so highly useful to man, or so much
valued by him, that the closest attention should be paid to even the
slightest deviation in the qualities or structure of each individual.
Pages:
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66