rns of the two sexes in one
Indian breed of goats. The bull zebu is said to have a larger hump than
the cow. In the Scotch deer-hound the two sexes differ in size more
than in any other variety of the dog,[162] and, judging from analogy,
more than in the aboriginal parent-species. The peculiar colour called
tortoise-shell is very rarely seen in a male cat; the males of this
variety being of a rusty tint. A tendency to baldness in man before the
advent of old age is certainly inherited; and in the European, or at
least in the {74} Englishman, is an attribute of the male sex, and may
almost be ranked as an incipient secondary sexual character.

In various breeds of the fowl the males and females often differ
greatly; and these differences are far from being the same with those
which distinguish the two sexes in the parent-species, the _Gallus
bankiva_; and consequently have originated under domestication. In
certain sub-varieties of the Game race we have the unusual case of the
hens differing from each other more than the cocks. In an Indian breed
of a white colour stained with soot, the hens invariably have black
skins, and their bones are covered by a black periosteum, whilst the
cocks are never or most rarely thus characterised. Pigeons offer a more
interesting case; for the two sexes rarely differ throughout the whole
great family, and the males and females of the parent-form, the _C.
livia_, are undistinguishable; yet we have seen that with Pouters the
male has the characteristic quality of pouting more strongly developed
than the female; and in certain sub-varieties[163] the males alone are
spotted or striated with black. When male and female English
carrier-pigeons are exhibited in separate pens, the difference in the
development of the wattle over the beak and round the eyes is
conspicuous. So that here we have instances of the appearance of
secondary sexual characters in the domesticated races of a species in
which such differences are naturally quite absent.

On the other hand, secondary sexual characters which properly belong to the
species are sometimes quite lost, or greatly diminished, under
domestication. We see this in the small size of the tusks in our improved
breeds of the pig, in comparison with those of the wild boar. There are
sub-breeds of fowls in which the males have lost the fine flo