Abstract
The plumage of the F-1 males resulting from a cross in either direction between Barred Rocks and Brown Leghorns in general resembles that of the Barred Rock though the pattern is not strictly identical.
Spaced among the barred plumage are feathers, the so-called exceptional feathers, which may be completely identical with those of the Brown Leghorn male, or, while exhibiting both barred and leghorn characteristics in general, yet show a number of traits foreign to either parent. The occurrence of these exceptional feathers is practically entirely confined to the plumage regions in which barbules are restricted to the vicinity of the shaft and to the basal feather sections, the saddle, hackle, head and minor coverts.
The greater number of exceptional feathers possess a barred tip and leghorn base; the barred region may occupy one vane-half, or the margin only of the feather, in which case the transition takes place within individual barbs, and yet other variations.
Feathers similar to these have been described in hybrids resulting from a cross between Plymouth Rocks and Orloffs by Serebrovsky, 1 by Hertwig and Rittershaus 2 from a cross between Barred Rocks and Goldlack, and from a cross between Plymouth Rocks and Faver-olles by Kuhn. 3
Serebrovsky attributes the origin of the exceptional feathers to the loss of one sex-chromosome carrying the factors for barring in development; Hertwig and Rittershaus to the frequent loss of the part of the X-chromosome containing the factor which inhibits black and white regions of barred feathers. Both Kuhn and Hertwig and Rittershaus state that exceptional follicles always produce exceptional feathers identical in pattern with the exceptional feathers plucked.
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