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From Thomas Davidson   29 December 1856

Summary

His experience confirms CD’s view that some species and even some genera of Brachiopoda are consistently more variable than others, and that such variable forms are variable in all localities and at all periods. Similarly a species that shows a lack of variability does so at all points in time and space. Discusses the causes of variability. [See Natural selection, p. 106.]

Author:  Thomas Davidson
Addressee:  Charles Robert Darwin
Date:  29 Dec 1856
Classmark:  DAR 162: 116
Letter no:  DCP-LETT-2024

From Thomas Davidson   3 May 1861

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Summary

Sends three tables on the known geological distribution of genera and subgenera of Brachiopoda. Has been continually puzzled by intermediate forms, and is convinced that the greater number of species can be linked together. "Natura non facit saltum."

Author:  Thomas Davidson
Addressee:  Charles Robert Darwin
Date:  3 May 1861
Classmark:  DAR 99: 1–2
Letter no:  DCP-LETT-3135
Document type
letter (2)
Author
Addressee
Darwin, C. R.disabled_by_default
Correspondent
Darwin, C. R.disabled_by_default
Davidson, Thomasdisabled_by_default
Date
1856 (1)
1861 (1)