To Thomas Davidson 23 December [1856]
Summary
Asks TD about variation among brachiopods.
Author: | Charles Robert Darwin |
Addressee: | Thomas Davidson |
Date: | 23 Dec [1856] |
Classmark: | American Philosophical Society (Mss.B.D25.142) |
Letter no: | DCP-LETT-2021 |
To Thomas Davidson 26 April 1861
Summary
Asks TD to carry out research on brachiopods to see whether the forms in one formation are intermediate between those above and below.
Describes unpublished study of spirifers by J. W. Salter.
Author: | Charles Robert Darwin |
Addressee: | Thomas Davidson |
Date: | 26 Apr 1861 |
Classmark: | DAR 143: 372 |
Letter no: | DCP-LETT-3128 |
To Thomas Davidson 30 April 1861
Summary
Thanks TD for his letter. Difficulties with CD’s theory are many and great, but CD thinks the reason is that we underestimate our ignorance. The imperfection of the geological record counts heavily for CD. His greatest trouble is weighing "the direct effects … of changed conditions of life without any selection, with the action of selection on mere accidental (so to speak) variability. I oscillate much on this head, but generally return to my belief that the direct [effects] … have not been great."
Is surprised that any one, like W. B. Carpenter, can go as far as to believe all birds may have descended from one parent, but will not go further and include all the members of the same great division. Such beliefs make "Divine mockeries" of morphology and embryology, the most important of all subjects.
Author: | Charles Robert Darwin |
Addressee: | Thomas Davidson |
Date: | 30 Apr 1861 |
Classmark: | DAR 143: 373 |
Letter no: | DCP-LETT-3131 |
To Thomas Davidson 7 April 1873
Summary
Thanks TD for catalogue of his Cretacean fossils.
Regrets he cannot visit Brighton.
Author: | Charles Robert Darwin |
Addressee: | Thomas Davidson |
Date: | 7 Apr 1873 |
Classmark: | American Philosophical Society (Mss.B.D25.426) |
Letter no: | DCP-LETT-8845 |
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
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 |
letter | (6) |
Darwin, C. R. | (4) |
Davidson, Thomas | (2) |
Davidson, Thomas | (4) |
Darwin, C. R. | (2) |