BIRDS— SEXUALLY LIMITED INHERITANCE. 439 



namely, whether the transmission of a character, which is at 

 first inherited by both sexes, can be subsequently limited in its 

 transmission to one sex alone by means of natural selection. We 

 must bear in mind, as shown in the preliminary chapter on sexual 

 selection, that characters which are limited in their development 

 to one sex are always latent in the other. An imaginary illustra- 

 tion will best aid us in seeing the difiiculty of the case: we may 

 suppose that a fancier wished to make a breed of pigeons, in 

 which the males alone should be colored of a pale blue, whilst the 

 females retained their former slaty tint. As with pigeons char- 

 acters of all kinds are usually transmitted to both sexes equally, 

 the fancier would have to try to convert this latter form of in- 

 heritance into sexually-limited transmission. All that he could 

 do would be to persevere in selecting every male pigeon which 

 was in the least degree of a paler blue; and the natural result 

 of this process, if steadily carried on for a long time, and if the 

 pale variations were strongly inherited or often recurred, would 

 be to make his whole stock of a lighter blue. But our fancier 

 would be compelled to match, generation after generation, his 

 pale blue males with slaty females, for he wishes to keep the 

 latter of this color. The result would generally be the production 

 either of a mongrel piebald lot, or more probably the speedy and 

 complete loss of the pale-blue tint; for the primordial slaty 

 color would be transmitted with prepotent force. Supposing, 

 however, that some pale-blue males and slaty females were pro- 

 duced during each successive generation, and were always crossed 

 together; then the slaty females would have, if I may use the 

 expression, much blue blood in their veins, for their fathers, 

 grandfathers, &c., will all have been blue birds. Under these cir- 

 cumstances it is conceivable (though I know of no distinct facts 

 rendering it probable) that the slaty females might acquire so 

 strong a latent tendency to pale-blueness, that they would not 

 destroy this color in their male offspring, their female offspring 

 still inheriting the slaty tint. If so the desired end of making a 

 breed with the two sexes permanently different in color might 

 be gained. 



The extreme importance, or rather necessity in the above case 

 of the desired character, namely, pale-blueness, being present 

 though in a latent state in the female, so that the male offspring 

 should not be deteriorated, will be best appreciated as follows: 

 the male of Scemmerring's pheasant has a tail thirty-seven 

 Inches in length, whilst that of the female is only eight inches; 

 the tail of the male common pheasant is about twenty inches, 

 and that of the female twelve inches long. Now if the female 

 Scemmerring pheasant with her short tail were crossed with the 

 male common pheasant, there can be no doubt that the male 



