Uhap. VIII. 
SEXUAL SELECTION. 
293 
our rule; for it is generally caused by intemperance 
after early youth, and is transmitted from the father 
to his sons in a much more marked manner than to his 
daughters. 
In the various domestic breeds of sheep, goats, and 
cattle, the males differ from their respective females 
in the shape or development of their horns, forehead, 
mane, dewlap, tail, and hump on the shoulders; and 
these peculiarities, in accordance with our rule, are not 
fully developed until rather late in life. With dogs, 
the sexes 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 will account, 
according to our rule, for his increased size being trans- 
mitted to his male offspring alone. On the other hand, 
the tortoise-shell colour of the hair, which is confined 
to female cats, is quite distinct at birth, and this case 
violates our 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 pigeon the fall develop- 
ment of the wattle and the crop occurs rather late in 
life, and these characters, conformably with our rule, 
are transmitted in full perfection to the males alone. 
The following cases perhaps come within the class pre- 
viously alluded to, in which the two sexes have varied 
in the same manner at a rather late period of life, and 
have consequently transferred their new characters to 
both sexes at a corresponding late period ; and if so, 
such cases are not opposed to our rule. Thus there 
nre sub-breeds of the pigeon, described by Neumeis- 
