240 



Genetic Studies in Poultry 



air, is a point we have not yet determined. We are inclined to attribute 

 the appearance of the ghost barring to the bird's being heterozygous 

 for the inhibitor of melanic pigment. It is certain that the ghost bars 

 occupy the position of the black bars in a gold or a silver barred bird. 

 For a white bird sometimes puts up a feather which is silver barred, 

 and occasionally the silver barring is confined to one side of the rachis. 

 In such cases the ghost bars are continuous with the black bars across 

 the feather. 



Whether the ghost barring is a heterozygous character we hope to 

 determine next season by breeding from these heterozygous whites, and 

 in order to make our view clear we may indicate what we expect to be 

 the composition of the F., generation. Denoting the factor for the in- 

 hibitor of gold pigment by S, and that for the inhibitor of melanic 

 pigment by X, we suppose the genetic constitution of the F^ birds to 

 be SsXx. The gametes of the F^ (/ should therefore be SX, Sx, sX, sx. 

 Since S is sex-linked the female-producing gametes of the F^ % will be 

 sX and sx, while the male-producing will be SX and Sx. The nature 

 of the F2. generation to be expected is indicated in Fig. 2. 



males 



females 



Fig. 2. 

 Five different kinds of birds are to be looked for on this hypothesis, 

 though, as shewn in the appended table, the distribution of these be- 

 tween the sexes should be very different. 



Further work however must shew whether this is the correct inter- 

 pretation. 



