The American Naturalist Volume 48

The American Naturalist Volume 48

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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. 1914 edition. Excerpt: that a white or unpigmented area is produced. It is not rare among mammals to find that one or more of the characteristic sorts of pigments are not produced in certain individuals and probably the factor or factors for these are lost altogether from the somatic and sex cells alike. Such variations may be perpetuated through inbreeding and so no doubt have arisen sundry domestic color varieties of animals and plants. For example, in the course of experiments with color varieties of the house mouse (carried on some years since with Professor W. E. Castle) we found that the chocolate-colored mice which we bred as extracted recessives from black mice, contained only chocolate pigment in their hair, whereas in the black parents both black and chocolate pigments were present, but the black masked a chocolate pigment. Moreover, the chocolate mice always bred true to that color, but if bred back to the black parents, gave black young or both black and chocolate in Mendelian proportions, according to the nature of the matings. The interesting point here is that the chocolate mouse once produced, through the loss of its black-and-gray-pigmentpotentiality, can transmit no other pigment character but the chocolate. What causes the occasional production of an individual in which one or more of the characteristic sorts of pigment is absolutely lacking is still unexplained. Nevertheless it is of frequent occurrence not only among domesticated species, in which the natural conditions of life are so greatly modified, but also in species in a state of nature. A skunk normally marked, but chocolate instead of black, a raccoon likewise of normal pattern but the pigmented areas yellow, are merely examples of the dropping out of the factor for black more

Product details

  • Paperback | 226 pages
  • 189 x 246 x 12mm | 413g
  • United States
  • English
  • black & white illustrations
  • 1236816706
  • 9781236816702