MENDELIAX EXPERIMENT ON FOWLS. 179 



that according to theory Pile first came from crossing Black-red 

 with white, but that snch a cross cannot now be made because 

 there are now no pure white Game, all our whites being " spoits " 

 from Brown-reds, which bred inter se, always breed white, but 

 which if put to any other colour would at once produce " colour " 

 and most likely that colour would be Pile. 



We have now to consider the theory or exj>lanation of the 

 origin of the Pile coloration. My experiments show that a 

 recessive pile is produced by crossing recessive White Silky with 

 dominant Black-red, and it therefore seems piobable that a 

 dominant Pile would be produced by crossing dominant white 

 Avith Black-red, or perhaps other colour. Such crosses I have not 

 yet tried, but hope to do so in future. With regard to mj^ 

 recessive Pile it would seem that the simplest explanation is that 

 segregation is not complete or perfect, but that the chromosomes 

 of the white parent, originally without any colour factor, in the 

 segregation of gametes in the heterozygote take with them some 

 of the substance of the colour-bearing chromosomes, and so cause 

 the development of colour. It must be remembered that the 

 Black-red itself is pied : that is to say, in the cocks the black and 

 red are in separate areas, almost completely exclusive of one 

 another ; although in the hens these colours ai'e more mingled, but 

 with reddish brown preponderating on the bi^east and abdomen. 

 The black segregates more completely than the red, but not quite 

 completely, since there ai'e black feathers or traces of black in the 

 Piles. It is impossible to suggest that the black is dominant and 

 the red recessive, for in that case the F^ would be black and white 

 pied. The recessive pile then, having a certain amount of 

 dominant red or reddish brown with recessive white, might be 

 expected to segregate, and the efiects of such segregation would 

 be visible when the piles wei'e bred inter se. That such a 

 segregation does not occur completely is shown by the fact that 

 all the offspring produced by pile x pile have some amount of 

 colour, but the fact that this amount of colour vai-ies in the 

 individuals may indicate that a varying degree of segregation 

 occurs, and probably by Selective mating a pure white could be 

 again produced. 



The fact, however, demonstrated in the expei'iments of Bateson 

 and Punnett* that when the Silky is crossed with a certain other 

 recessive white, completely coloured black-red l)irds are produced 

 in Fj just as ci"0ssing of two white races of Sweet Pea may 

 produce completely coloured ilowers, suggests that the origin of 

 the recessive pile in my experiments may require a more com- 

 plicated explanation. Accoixling to Bateson, the colour must be 

 due to two factors X and Y, and when either of these is absent 

 the bird is white. In the case of the two recessive whites pro- 

 ducing colour when mated, one has one colour-factor absent, the 

 other the other, so that when fertilization takes place the two 

 factors X, Y are both present and fully developed colour results, 

 * Bateson, 'Mendel's Principles of Hevedity,' 1909, p. 103, 



