IO2 White Fowls [CH. 



a series of facts which perhaps, better than any other, 

 illustrate the impossibility of understanding the significance 

 of genetic phenomena without minute individual analysis. 



In poultry we know at least four different sorts of white 

 plumage, each with its own special properties. As far as 

 external appearances of the adults go there is little or 

 nothing which would lead an observer to suspect that the 

 genetic powers or capabilities of these four types were 

 entirely distinct in respect of colour. 



In the first type the white acts as a dominant. Generally 

 speaking when a purely white variety such as White Leg- 

 horn is crossed with a coloured variety, such as Indian 

 Game or Brown Leghorn, F^ is, in the newly hatched 

 condition, white with a few specks of black. The black 

 then present may be confined to a single hair, but we have 

 met very few instances of total absence of such a speck or 

 "tick" as it is called. As the down is replaced by feathers 

 similar ticks of black and brown appear in them. The 

 position and amount of the ticks in the feathers bear no 

 obvious relation to the down-ticks. These F^ birds, however, 

 at all ages are substantially white birds, the amount of 

 colour though definite, being almost always insignificant. 

 Exceptions occur in the case of cocks, which sometimes 

 have enough red in the wings to bring them into the 

 category called by fanciers "pile," though they are of the 

 usual white in the downy stage. 



We may thus speak of White Leghorn as a dominant 

 white. F 2 from such an F l generation consists of a great 

 variety of colours, the relations of which have not been 

 worked out. 



But among the derivatives from various matings* which 

 Mr Punnett and I have carried out white birds have been 

 produced which are, so far as their whiteness is concerned, 

 simple recessives to colour. Sometimes, but not always, they 

 have ticks of grey colour. These recessive whites breed 

 true to whiteness as the White Leghorns do, and no one 

 looking at them would doubt for a moment that they were 

 moderate specimens of that breed. 



In addition to these the white of White Rosecomb 



* These birds arose from a mixture of Brown Leghorn, White Dorking 

 and Indian Game. See Rep. Evol. Ctee, in. p. 19. 



