Chap. VIII. 
SEXUAL SELECTION. 
285 
to change his whole stock, including both sexes, into 
this tint. If, however, variations of the desired tint 
appeared, which were from the first limited in their 
development to the male sex, there would not be the 
least difficulty in making a breed characterised by the 
two sexes being of a different colour, as indeed has been 
effected with a Belgian breed, in which the males alone 
are streaked with black. In a similar manner, if any 
variation appeared in a female pigeon, which was from 
the first sexually limited in its development, it would 
be easy to make a breed with the females alone thus 
characterised ; but if the variation was not thus originally 
limited, the process would be extremely difficult, per- 
haps impossible. 
On the 'Relation between the period of Development of a 
Character and its transmission to one sex or to both sexes . 
— Why certain characters should be inherited by both 
sexes, and other characters by one sex alone, namely by 
that sex in which the character first appeared, is in most 
cases quite unknown. We cannot even conjecture why 
with certain sub-breeds of the pigeon, black strise, though 
transmitted through the female, should be developed in 
the male alone, whilst every other character is equally 
transferred to both sexes. Why, again, with cats, the 
tortoise-shell colour should, with rare exceptions, be 
developed in the female alone. The very same cha- 
racters, such as deficient or supernumerary digits, colour- 
blindness, &c., may with mankind be inherited by the 
males alone of one family, and in another family by the 
females alone, though in both cases transmitted through 
the opposite as well as the same sex . 23 Although we 
are thus ignorant, two rules often hold good, namely 
23 References are given in my 4 Variation of Animals under Domes- 
tication/ vol. ii. p. 72. 
