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 bettveen 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 striae, 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 



Zi Eefercnces are given in my ' Variation of Animals under Domes- 

 tication,' vol. ii. p. 72. 



