The Descent of Man

of dogs do not differ, except that in certain
breeds, especially in the Scotch deer-hound, the
male is much larger and heavier than the female;
and, as we shall see in a future chapter, the
male goes on increasing in size to an unusually
late period of life, which, according to rule, will
account for his increased size being transmitted
to his male offspring alone. On the other hand,
the tortoise- shell colour, which is confined to
female cats, is quite distinct at birth, and this
case violates the rule. There is a breed of pigeons
in which the males alone are streaked
with black, and the streaks can be detected
even in the nestlings; but they become more
conspicuous at each successive moult, so that
this case partly opposes and partly supports the
rule. With the English Carrier and Pouter pigeons,
the full development of the wattle and
the crop occurs rather late in life, and conformably
with the rule, these characters are
transmitted in full perfection to the males alone.
The following cases perhaps come within