Ciiap. VIII. 
SEXUAL SELECTION. 
283 
tion ; but a few instances may here be given. There 
are breeds of the sheep and goat, in which the horns 
of the male differ greatly in shape from those of the 
female ; and these differences, acquired under domes- 
tication, are regularly transmitted to the same sex. 
With tortoise-shell cats the females alone, as a general 
rule, are thus coloured, the males being rusty-red. 
With most breeds of the fowl, the characters proper 
to each sex are transmitted to the same sex alone. So 
general is this form of transmission that it is an ano- 
maly when we see in certain breeds variations trans- 
mitted equally to both sexes. There are also certain 
sub-breeds of the fowl in which the males can hardly 
be distinguished from each other, whilst the females 
differ considerably in colour. With the pigeon the 
sexes of the parent-species do not differ in any external 
character; nevertheless in certain domesticated breeds 
the male is differently coloured from the female . 22 
The wattle in the English Carrier pigeon and the crop 
in the Pouter are more highly developed in the male 
than in the female ; and although these characters have 
been gained through long-continued selection by man, 
the difference between the two sexes is wholly due to 
the form of inheritance which has prevailed ; for it 
has arisen, not from, but rather in opposition to, the 
wishes of the breeder. 
Most of our domestic races have been formed by the 
accumulation of many slight variations ; and as some 
of the successive steps have been transmitted to one 
sex alone, and some to both sexes, we find in the diffe- 
rent breeds of the same species all gradations between 
great sexual dissimilarity and complete similarity. In- 
22 Dr. Chapnis, ‘ Le Pigeon Voyageur Beige,’ 1865, p. 87. Boitard 
et Corbie, ‘Les Pigeons de Voliere,’ &c., 1824, p. 173. 
