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 is correlated with another variation of greater momentum or vital value. Another result of modern studies on varia¬ tion requires to be stated very cautiously. Evidence is accumulating to show that organic structure may pass with seeming abruptness from one position of equilibrium to another. Changes of considerable amount sometimes occur at a single leap. These brusque changes are called 44 discontinuous variations,” or sometimes 44 sports,” and, in certain cases, 44 mutations.” There is nothing new in the suggestion that evolution may sometimes have been by leaps and bounds, for this was a favourite idea of Cuvier’s evolu- * tionist contemporary and antagonist, Etienne Geoffroy Saint-Hilaire; and it was also a pet heresy of Huxley’s. There is nothing new in recognizing that discontinuous variations do occur, for they correspond to Darwin’s 44 single variations ” or 44 sports.” What is new is that we are beginning to accumulate facts in regard to their frequency and their heritability. Sir Francis Gaiton compared organic struc¬ ture to a polygonal model, so shaped as to stand on any one of its sides. 44 The model and the organic structure have the cardinal fact in common, that if either is disturbed without transgressing the range of its stability,