Use-inheritance illustrated by the direction of hair on the bodies of animals / by Walter Kidd.

  • Kidd, Walter (Walter Aubrey), 1852-
Date:
1901
Catalogue details

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

Credit: Use-inheritance illustrated by the direction of hair on the bodies of animals / by Walter Kidd. Source: Wellcome Collection.

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    SLOPE OF НАШ ON THE BODIES OF ANIMALS 29 for convenience, the Exceptional type. The reason for provisionally calling this type Exceptional is that a marked reverse of slope such as this may legitimately be considered to need some exceptional interpretation. The term Normal type may be applied to that slope on the extensor surface which passes in a uniform distal direction, in keeping with that on other surfaces of the limb. This is found very largely in Ungulates, and a list of the exceptions to this rule among Ungulates is given in the Proceedings of the Zoological Society of London, June 19, 1900, p. 686. It is unnecessary here to dwell minutely on the distribu¬ tion of these two types among kindred or differing forms. It is sufficient to state that the two main types exist in the Mammalian orders to an extent that would not be expected from the close similarity of structure presented by those forms, which show marked differences in respect of this character. This and all other features of the bodies of animals are open to one of three interpretations ;— 1st. That by original creation of large groups of animals, these were so produced as being suited to their lives and habits. 2nd. That they are adaptive modifications governed by natural selection. 3rd. That they are inherited modifications, produced by use or habit. Certain of such characters have been claimed to be vesti¬ gial ; but if they can be shown not to be open to selectionist interpretations at the present time, a fortiori they cannot be vestigial, and in any case the number of these must be ex¬ tremely small. It remains to ask which of these three is the most scientific and probable. The first must be left out of account in a purely scientific discussion of such points as the aetiology
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