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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    it was formerly supposed that all variation must be, a progress from a lower degree of complexity to a higher, but the converse. When from a single wild type man succeeds in producing a multitude of new varieties, we may speak of the result as a progress in differentiation : but we must recognize that the term is only applicable loosely, and that the obvious appearance of increased com¬ plexity may in reality be the outcome of a process of simplification.99 Similarly, 44 rever¬ sion occurs when the sum total of the factors returns to that which it has been in some original type.55 The return may be brought about by the omission of an element or by the addition of a missing element. If certain kinds of variation may be called 64 unpacking,59 reversion is re-packing. In discussing the bearing of Mendelism on the theory of evolution, Bateson makes three important suggestions. (1) 44 One has only to glance over trays of birds9 skins, the port¬ folios of a herbarium, or drawers of butterflies and moths, to discover abundant 4 species 9 which are analytical varieties of others,99 i. e. differing in the presence or absence of definite factors. 44 The principles of heredity we trace in our experimental breeding are operat¬ ing throughout the natural world of species.9*