rited effect as in the period of the
flowering of plants when transported from one climate to another. With
animals the increased use or disuse of parts has had a more marked
influence; thus I find in the domestic duck that the bones of the wing
weigh less and the bones of the leg more, in proportion to the whole
skeleton, than do the same bones in the wild duck; and this change may
be safely attributed to the domestic duck flying much less, and walking
more, than its wild parents. The great and inherited development of the
udders in cows and goats in countries where they are habitually milked,
in comparison with these organs in other countries, is probably another
instance of the effects of use. Not one of our domestic animals can be
named which has not in some country drooping ears; and the view which
has been suggested that the drooping is due to disuse of the muscles of
the ear, from the animals being seldom much alarmed, seems probable.

Many laws regulate variation, some few of which can be dimly seen, and
will hereafter be briefly discussed. I will here only allude to what may
be called correlated variation. Important changes in the embryo or larva
will probably entail changes in the mature animal. In monstrosities,
the correlations between quite distinct parts are very curious; and many
instances are given in Isidore Geoffroy St. Hilaire's great work on this
subject. Breeders believe that long limbs are almost always accompanied
by an elongated head. Some instances of correlation are quite whimsical;
thus cats which are entirely white and have blue eyes are generally
deaf; but it has been lately stated by Mr. Tait that this is confined to
the males. Colour and constitutional peculiarities go together, of which
many remarkable cases could be given among animals and plants. From
facts collected by Heusinger, it appears that white sheep and pigs
are injured by certain plants, while dark-coloured individuals escape:
Professor Wyman has recently communicated to me a good illustration of
this fact; on asking some farmers in Virginia how it was that all their
pigs were black, they informed him that the pigs ate the paint-root
(Lachnanthes), which coloured their bones pink, and which caused
the hoofs of all but the black varieties to drop off; and one of the
"crackers" (i.e. Virginia squatters) added, "we select the black members
of a litter for raising, as they alone have a good chance of living."
Hairless dogs have imp