150 SEXUAL SELECTION: BIRDS. [Part II 



Our fancier, in order to make liis new breed with the 

 males of a decided pale-blue tint, and the females un- 

 changed, would have to continue selecting the males during 

 many generations ; and each stage of paleness would have 

 to be fixed in the males, and rendered latent in the fe- 

 males. The task would be an extremely difficult one, and 

 has never been tried, but might possibly succeed. The 

 chief obstacle would be the early and complete loss of the 

 pale-blue tint, from the necessity of reiterated crosses with 

 the slaty female, the latter not having at first any latent 

 tendency to produce pale-blue offspring. 



On the other hand, if one or two males were to vary 

 ever so slightly in paleness, and the variations were from 

 the first limited in their transmission to the male sex, the 

 task of making a new breed of the desired kind would be 

 easy, for such males would simply have to be selected and 

 matched with ordinary females. An analogous case has 

 actually occurred, for there are breeds of the pigeon in 

 Belgium 4 in which the males alone are marked with black 

 stria?. In the case of the fowl, variations of color limited 

 in their transmission to the male sex habitually occur. 

 Even when this form of inheritance prevails, it might 

 well happen that some of the successive steps in the 

 process of variation might be transferred to the female, 

 who would then come to resemble in a slight degree the 

 male, as occurs in some breeds of the fowl. Or again, the 

 greater number, but not all, of the successive steps might 

 be transferred to both sexes, and the female would then 

 closely resemble the male. There can hardly be a doubt 

 that this is the cause of the male pouter pigeon having a 



Is only six inches long, ' Planches coloiiees,' vol. v. 1838, pp. 4*78, 498 : 

 the measurements above given were made for me by Mr. Sclater. For 

 the common pheasant, see Macgillivray, 'Hist. British Birds,' vol. i. pp. 

 118-121. 



4 Dr. Chapuis, 'Le Pigeon Voyageur Beige,' 1865, p. 87. 



