Conditions Modifying the Expression of Silver in the Silver Campine Fowl

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Abstract
The suppression of red in the plumage of many breeds of domestic fowl is primarily due to the presence of a dominant, sex-linked gene Silver. In the Silver Campine this suppression was found to be incomplete after castration. Large numbers of red melanophores appeared in the developing capon feather germs and considerable red pigment was present in the mature feathers. This production of red pigment could again be suppressed by the injn. of either [male] or [female] sex hormones. The complete expression of Silver, therefore, appears to be dependent upon an adequate sex hormone level. Injn. of testosterone propionate into the albumin of Silver Campine eggs failed to inhibit the appearance of red pigment in the down plumage. This indicates that an age factor is also involved in the expression of Silver. Possible developmental relations of black and red melanophores are discussed in the light of the changes produces by hormone injns.