Heredity in the light of recent research / by the late L. Doncaster.

  • Leonard Doncaster
Date:
1921
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Heredity in the light of recent research / by the late L. Doncaster. Source: Wellcome Collection.

    34/184 page 18
    18 HEREDITY would be obtained having two maxima, one near 62 and another near 68. Yet the stature might be a definite sexual character, and hence essentially as discontinuous as the sexes themselves. This distinc¬ tion between continuous and discontinuous variation may seem unimportant in itself, but when its in¬ heritance is considered the distinction becomes of the first importance. Clearer examples of discontinuous variation are given by such characters as colour, or by organs which are repeated in series, such as vertebrae and ribs, the segments of a worm or the petals of a Аолуег. When variation occurs in this latter group it is generally complete, so that the different forms are visibly discontinuous. In the case of colour in the skin or hair in animals, or petals of flowers, discontinuity is sometimes less apparent, and grading frequently occurs, but even in apparently graded cases the inheritance of the character may often reveal discontinuity. For example, a piebald animal might be thought to be intermediate between the fully-coloured and albino (white with no pigment), but breeding tests would at once show that piebald- ness was an independent character, which cannot be regarded as in any sense intermediate between the other two conditions except in general appearance. The same applies to such cases as the * silver ' cat or rabbit, or the pale purple sweet-pea; the cause of
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