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

  • Doncaster, L. (Leonard), 1877-1920.
Date:
1910
Catalogue details

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

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

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    П] HEREDITY 9 extent from very small to considerable range. They therefore founded their theory on this type of variability rather than on the occurrence of con¬ siderable ^occasional variations' which are not connected with the type by a series of intermediates. It was not, however, until after the theory of Natural Selection had obtained general recognition, that any detailed study was undertaken of the actual frequency and extent of variation, and its mode of occurrence. The accurate investigation of variation has thus been in progress only fer some twenty or twenty-five years, and according to the methods adopted students have become divided into two somewhat distinct schools. One of these has devoted itself rather to the attempt to observe and classify the different kinds of variation, and the other, generally called the ' biometrician ' school, to measure its frequency and range. It will be convenient to consider the results obtained by the second method first. If a character is chosen which can be accurately measured, such as human stature, and a sufficiently large number of individuals are observed, it will commonly be found that there is considerable range of variation, and that every gradation in size occurs between the smallest and largest. Such variation is spoken of as ^continuous,' as opposed to 'discontinu¬ ous' variation in which individuals of two kinds occur.