Evolution / by Patrick Geddes and J. Arthur Thomson.

  • Patrick Geddes
Date:
[1911?]
Catalogue details

Licence: Public Domain Mark

Credit: Evolution / by Patrick Geddes and J. Arthur Thomson. Source: Wellcome Collection.

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    reproductive system acting irregularly and producing variations. But that variation is not exclusively associated with sexual repro¬ duction is demonstrated by the case of plants sporting 55 through bud-variation. Such eases, moreover, prove that the nature of the organism counts for more than the conditions. Changed habits, e.g. changes in the degree of use or disuse of a part, produce an inherited effect, witness the lighter wing-bones and heavier leg-bones of the domestic duck, or the enlarged udders of cows. Variations are often definitely correlated : thus short-beaked pigeons have small feet; hairless dogs have imperfect teeth; and blue¬ eyed white tom-cats are deaf. Hence selec¬ tion of any one character will probably modify others indirectly. Although the laws of inheritance are mostly unknowm, it seems that probably most, if not all, characters tend to be inherited. There is no satisfactory evidence to support the popular idea that domestic varieties revert to the primitive stock when they run wild. Reversions occasionally occur in domestica¬ tion, but there is no general tendency to lose what has been gained—apart, of course, from breeding with wild stocks, or with other domesticated ones.