nd,
although they may be kept alive, they pine and "rarely come to any
good." Yet the animal which _acquires_ least tameness--or apparently,
indeed, none at all--inherits most! It appears, in fact, to inherit that
which it cannot acquire--a circumstance which indicates the selection of
spontaneous variations rather than the inheritance of changed habits.
Such variations occasionally occur in animals in a marked degree. Of a
litter of wolf-cubs, all brought up in the same way, "one became tame
and gentle like a dog, while the others preserved their natural
savagery." Is it not probable that permanent domestication was rendered
possible by the inevitable selection of spontaneous variations in this
direction? The _excessive_ tameness, too, of the young rabbit, while
easily explicable as a result of unconscious selection, is not easily
explained as a result of acquired habit. No particular care is taken to
tame or teach or domesticate rabbits. They are bred for food, or for
profit or appearance, and they are left to themselves most of their
time. As Sir J. Sebright notices with some surprise, the domestic rabbit
"is not often visited, and seldom handled, and yet it is always tame."

MODIFICATIONS OBVIOUSLY ATTRIBUTABLE TO SELECTION.

Innumerable modifications in accordance with altered use or disuse, such
as the enlarged udders of cows and goats, and the diminished lungs and
livers in highly bred animals that take little exercise, can be readily
and fully explained as depending on selection. As the fittest for the
natural or artificial requirements will be favoured, natural or
artificial selection may easily enlarge organs that are increasingly
used and economize in those that are less needed. I therefore see no
necessity whatever for calling in the aid of use-inheritance as Darwin
does, to account for enlarged udders, or diminished lungs, or the thick
arms and thin legs of canoe Indians, or the enlarged chests of
mountaineers, or the diminished eyes of moles, or the lost feet of
certain beetles, or the reduced wings of logger-headed ducks, or the
prehensile tails of monkeys, or the displaced eyes of soles, or the
altered number of teeth in plaice, or the increased fertility of
domesticated animals, or the shortened legs and snouts of pigs, or the
shortened intestines of tame rabbits, or the lengthened intestines of
domestic cats, &c.[44] Changed habits and the requisite change of
structure will usually be favoured by na