Charles Davenport letter to Karl Pearson, defending roles of mutation and environment in evolution in paper rejected by Biometrika (6/5/1903) (4)

2125. [5-6-03] the slight individual variations as such a factor. Wilden's[?] work on crabs seems to me the best but even then the [crossed out 'work'] effect wrought, was not great (although the time was certainly short), and we don't yet know how [crossed out type] great a modification will be eventually produced[?]. DeVrie's experiments are certainly instructive as to the increasing difficulty of producing modifications as we depart farther & farther from the [illegible] condition, and my agriculture friends state that they have the same experience. You say that I practically throw Darwin out & adopt a Mutation Theory. I do not lay great stress on Natural Selection because this has, evidently, [obs type] as [underscore]originally conceived by Darwin[end underscore], little or nothing to do with variation. In the summary of Chapter IV Orig. of Species, 6th Ed he says: Considering the infinite complexity of the relations of all organic beings to each other & to their [underscore]conditions of life,[end underscore] causing [open bracket]N.B. [underscore]conditions[end underscore] cause; not nat. select.[closing bracket] an infinite diversity in structure, constitution, & habits, & be advantageous to them, it would be a most extraordinary fact, if no variations ever occurred useful to each being's own welfare .... But if variations useful to any organic being do occur, assuredly individuals thus characterized struggle for life". True Darwinism is a theory of adaptation. Darwin taught that variations were due to direct influence of environment; is it not you rather than I who would throw Darwinism over? Finally, you think to accept the possibility of Mutation [open bracket] as Darwin did[close bracket] and to insist on the great importance of the direct modifying effects of Environment [open bracket]as Darwin most emphatically did[close bracket] stultifies my paper & biometric work in general. This astounds me greatly. In your Gra[illegible] of Science p 379 after an analysis of the sources of Change you concluded, very judiciously, that "satisfactory numerical demonstration of its existence [open bracket]inheritance of the [illegible][close bracket] is wanting" and then go on to show how evolu [end]