194 Peculiar Pigmentation, of the Silki/ Fowl 



the constitution ffPPII or ffPPIi and suppose that in the presence 

 of a double dose of the pigmentation factor the effects of the inhibitor 

 are in considerable measure overcome in the younger stages. In cor- 

 i-oboration of this view we may state that we reared several of these 

 deeply pigmented ^^ and that they all became far less heavily pig- 

 mented in appearance as they approached maturity. In external 

 appearance indeed they showed little more pigmentation than the i^, 

 cocks. This explanation is the natural one if we regard the constitu- 

 tion of the slightly pigmented Fi % as FfPpIi, and further evidence 

 (p. 198) in favour of this view will be adduced from an entirely 

 different set of experiments. 



3. fj X Brown Leghorn. 



(o) Broiuii Leghorn % x F^ ^. 



[Nature of mating, FfppIi x fPpIi.'] 



On our hypothesis this form of mating should give a specific result, 

 for while the (^ ^ should all be either without, or with comparatively 

 little, pigment, one quarter of the % % should be fully pigmented 

 (cf. Figs. 3 and 4). We have bred a considerable number of birds 

 (nearly 700) in this way, and the figures given in Table V show that 

 this expectation is closely realised. None of the 336 c/',/ produced 



1006 



1907 



1908 



1909 



