236 Genetic Studies in Poultry 



Thanks to the work of Spillman, Morgan, Pearl and others in America 

 we realise that the barring depends upon a definite sex-linked factor 

 acting upon a black basis. The factor would appear to be of an inhibitory 

 nature, preventing the deposition of black pigment almost completely 

 in the lighter bands of the feathers, slightly so in the darker ones. The 

 action of the barring factor is also evident uj)on a brown basis, though 

 not so clearly. Some years ago Ave made a cross between Plymouth 

 Rock % and Brown Leghorn ^ . The ^i (/</ were barred like the Rock, 

 while the F^ %% were full black or nearly so. In the F^ generation 

 appeared more or less typical barreds and blacks of both sexes, together 

 with browns of various kinds (including silver-greys^), both barred and 

 unbarred. In these barred browns the barring was not nearly so sharp 

 as in the barreds belonging to the black class. For the present we are 

 disposed to consider that the barring factor acts more intensely upon 

 the black pigment than upon the golden pigment, if indeed it acts upon 

 the latter at all. On this view the blurred nature of the barred browns 

 would be due to the inhibition of only the black pigment scattered 

 about among the gold in the mixture which goes to make up the brown 

 bird. We realise that this can be no more than a plausible suggestion in 

 our present state of ignorance of the pigments of the fowl's plumage. 

 The point however deserves further investigation. 



As shewn by its behaviour towards black, the barring of the Ham- 

 burgh-Campine group is evidently different in its nature, though the 

 only direct evidence we know of is provided by some experiments carried 

 out a few years ago at Cambridge^. In those experiments a cross was 

 made between a Gold Pencilled Hamburgh ^ and a Black Langshan %. 

 The ^1 birds were black (with some gold in the hackles of the cocks), 

 and in F.^ some barred birds reappeai-ed. The barring of the Hamburgh 

 is evidently recessive to self colour in this case. But it does not neces- 

 sarily disappear completely on crossing. This year we mated a Gold 

 Campine $ with a Barred Rock ^ which was heterozygous in baning. 

 The cross resulted in approximately equal numbers of barred birds very 

 like Plymouth Rocks in plumage, and of birds wholly or predominantly 

 black. Certain of these last however shewed coarse silver barring in some 

 feathers, notably on the breast. This barring we suppose to have been 



' Evidently the silver factor was carried by the Pl3'mouth Rock ,^ . Of some birds we 

 bred this year, ex Gold Campine $ x Plymouth Eock ^ (heterozygous in barring), the 

 non-barred ones which were not full black all showed some silver markings. Here again 

 the Rock evidently carried silver. It seems not improbable that the silver factor may be 

 an ingredient essential to the barred pattern of the Rock Group. 



'^ Cf. Punnett and Bailey, Journal of Genetics, 1918 and 1920. 



