Carnegie Institution of Washington Publication Volume 179

Carnegie Institution of Washington Publication Volume 179

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 edition. Excerpt: ...carries agouti or not. She has had certain animals (sables) which were dark-pigmented except for a yellow belly. Such animals always molted out sables. She says "sables" are not to be confused with sooty yellows, which result from mating yellow with black, and are dirty color all over with no pattern. She finds that yellows crossed inter se may give"sables," and that "sables" crossed inter se may give yellows, and that matters are further complicated by the occurrence of so-called "reversed sables," in which the dark hairs had yellow tips and bases, with a dark subapical band. The writer must confess that he is unable to draw a clear line between "sables" and "sooty yellows" in all cases. The term sooty yellow is therefore intended in this paper to cover both varieties. It is possible to explain the appearance of sooty yellows on the basis of fluctuation in activity of the factor R, restriction. Thus, when R is present in full strength the animal is clear yellow; if R is slightly weaker, some dark pigment shows itself. The amount of dark pigment visible becomes progressively greater as the factor R becomes weaker or takes on a rhythmical activity. Thus, if R is hampered in activity during the growth of the first part of the hair, we have a dark tip formed. But if R comes into full activity again, a yellow band results, followed by a second weakening of R, resulting in a dark base to the hair. This would account for the superficial similarity to the agouti pattern. "Reversed sables" may possibly result from a reversal of the order in which the strong and weak periods of R occur. So, too, those very dark sooty yellows that lack the ticked-hair pattern may be considered...
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Product details

  • Paperback | 30 pages
  • 189 x 246 x 2mm | 73g
  • United States
  • English
  • black & white illustrations
  • 1236904656
  • 9781236904652