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Darwin Correspondence Project

From Thomas Davidson   3 May 1861

33 Park Crescent Brighton

3d May 1861

My Dear Sir.

I have to express my warmest thanks for your very kind and instructive letter of April the 30th. as well as for the valuable present of the last edition of your admirable work “Origin of Species.”1   it arrived last night, but I have not yet had time to peruse the chapters IX & X which I will D.V. do in a day or two being extremely pressed for time with work for the Pal. Soc. & my Indian paper for the Geol. Soc.—2

I can assure you that I shall give every attention to the subject of descent with modification, as suggested in your to me most interesting letters. I have not time alas to day to enter into details concerning the Brachiopoda, but shall not lose sight of the object & must be content at this moment to send you 3 little rough tables of the known distribution of the Brachiopoda—and which I consider to be as near the truth as the present state of our information will permit3   It is certain and no one can object to your statement relative to the great imperfection of Geological record (I was reading this morning some obs. upon the subject in the last number of the Geologist, for May 1861 just appeared).4 The Geological record is therefore very imperfect and the Palæontological record still more so—& I admit that you have a strong hold there for your theory.

Having myself on account of my monographs been obliged to examine every layer (if I may be permitted the expression) in search of Brachiopoda and to trace as far as possible the first appearance, duration, modification & extinction of each form, have been constantly (not now & then but almost every day) at a loss or puzzled what to do with intermediate shapes. did they belong to one or to the next or most closely allied species was the constant question. & more the material increased greater was the difficulty. Such work is sufficient to convince even the most incredulous of the variability of species & how a same species may become considerably modified by time and peculiar conditions— I have not the slightest doubt that by far the greater number of species of Brachiopoda could be even now linked together   The genera, perhaps also and the more our knowledge will extend the more closely will the whole become linked together   ‘Natura non facit saltum’ was my belief in 1848 & was so stated by me when I described the British Silurian Species in the Bulletin de la Soc. geol de France’5 and I believe that one might (tabulate the species as you propose) show a gradation & radiation, between many of the most extreme conditions.

[DIAG HERE]

We are very little acquainted with the rocks of the Cambrian period, but very few species of fossils have been found and that is our oldest record at present known— well in all we find orthis and Lingula only for the present, but any day might produce a larger number and especially so as you remark in the Lower Silurian the introduction of so many new genera or species. which we cannot believe to have been created for the first time then. Many of these may have been derived by modification from older strata (or from a period) still far more ancient than the upper Cambrian. When I conclude my work on the Brachiopoda I shall D.V. give a number of curious facts showing discent with modification, that many forms considered as distinct creation are only modifications.6 Still there are many difficulties in the way of fully realising the theory of a single creation, and I can well understand the trouble & time you have required in acquiring your conviction. I believe that the facts in Morphology & in Embryology will when more fully worked out, will cast considerable light upon many points at present but little known with reference to species.—

I am obliged to conclude this letter written in great haste, but cannot do so without once more thanking most sincerely for your very valuable communications as well as for the present of the new edition of your remarkable work.

Believe me Dear Sir | Yours very sincerely | Tho Davidson—

P.S. I forgot to say that I have not read Hookers “Introduction to the flora of Australia”,7 but when I next go to London will endeavour to get the loan of it from the Royal Soc. liby.— I have not published yet any thing upon the subject of your theory as I am still continually thinking over the matter, intending to do so at the conclusion of my work for the Pal Soc. I merely said two or three words upon the subject in a little paper published in the Geologist of which I forward a copy.8

to C. Darwin Esq. FRS.

[Enclosure]9

[Table I is entitled ‘Geological distribution at present known of the Genera & Sub-genera of Brachiopoda.’ A note at the top reads: ‘about 1950 so-termed species of Brachiopoda are described and arranged as follows’. On the left-hand side of the table, Davidson listed genus and subgenus names of brachiopods, each followed by attribution details and the name of a species from the genus. On the right-hand side Davidson drew eleven columns, each headed with the name of a geological period, from the ‘Upper Cambrian’ to ‘recent’. He indicated during which geological periods each genus or subgenus was extant by means of crosses entered in the appropriate columns. At the bottom of the table, Davidson wrote: ‘N.B a number of So-termed new Genera recently proposed by Prof. J. Hall,10 Mr. Billings11 and some others have been omited as their value is not yet determined, but in any case they would have to enter into one or another of these groups & would not alter the geological limits as here recorded.’

Table II is headed: ‘Showing the first appearance at present known of each genus.’ It also lists genus and subgenus names of brachiopods on the left; instead of crosses, Davidson used continuous bars spanning across the columns to indicate the duration of each form in the various geological periods.

Table III has the heading: ‘Showing the at present known duration of each great group.’ This table lists as the six ‘great groups’ of brachiopods: Orthis, Spirifer, Atrypa, Rhynchonella, Terebratula, and the ‘Unarticulated group Lingula Discina Crania etc.’

At the bottom of Tables II and III, which are placed side by side on one page, Davidson summarised the salient points presented in the two tables: 1   From this table it would appear 1st that the large genera such as Orthis, Leptæna, Rhynchonella, Crania, discina, Lingula, Chonetes, Productus, Athyris, Spiriferina, Terebratula, Terebratella, Thecideum Waldheimia & Terebratella had the longest duration in time— 2. That a great many so termed genera have not been found represented beyond the Palæozoic range or did not depart the upper limit of the Permian formation. 3. That it was during the Palæozoic Period that the Brachiopodous forms were most numerous & greatest variation in generic character prevailed.]

CD annotations

1.1 I have … copy. 7.6] scored pencil
7.2 but when … liby.— 7.3] cross in margin, pencil
7.3 I have … copy. 7.6] cross in margin, pencil

Footnotes

CD presented Davidson with a copy of the third edition of Origin (see letters to T. W. St C. Davidson, 26 April 1861 and 30 April 1861, and Correspondence vol. 9, Appendix VII).
Davidson refers to his monograph on fossil Brachiopoda (Davidson 1851–86), which was published by the Palaeontographical Society of London; he also cites his study of fossil forms of India (Davidson 1862) ‘D.V.’ is an abbreviation for ‘Deus vult’, ‘God wills it’.
See enclosure and n. 9, below.
The reference is to the second part of Hutton 1861, which puts forward explanations for the imperfection of the geological record.
Davidson 1848, p. 311.
In the next-published volume of his monograph, which appeared in 1863, Davidson mentioned the possibility that fossil brachiopods might provide evidence for CD’s view of species and varieties (Davidson 1851–86, 2: 212–13). He did not return to the question, however, until the final volume of his monograph, published shortly before his death. There Davidson quoted from CD’s letter of 26 April 1861 and stated (ibid., 5: 387): In several subsequent letters Darwin reiterated his suggestions; and, although I have not neglected a request coming from so eminent a quarter, I am bound to state that I have found the subject beset with so many apparently inexplicable difficulties that year after year has passed away without my being able to trace, in a satisfactory manner, the descent with modification among the Brachiopoda which the Darwinian doctrine requires. Davidson stated that he none the less believed in some form of the doctrine of species transmutation.
Davidson 1861, pp. 58–9. A lightly marked copy of Davidson’s paper is in the Darwin Pamphlet Collection–CUL. See letter to Thomas Davidson, 26 April 1861.
Owing to the difficulty of typesetting Davidson’s tables, only the table headings and a summary of their contents are provided.
Davidson may be referring to Hall 1860.
Elkanah Billings, a geologist employed by the Geological Survey of Canada, had recently described a number of new brachiopod genera (Billings 1859a and 1859b).

Bibliography

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

Davidson, Thomas. 1848. Mémoire sur les Brachiopodes du système silurien supérieur d’Angleterre. Bulletin de la Société Géologique de France 2d ser. 5 (1847–8): 309–53.

Davidson, Thomas. 1851–86. British fossil Brachiopoda. 6 vols. London: Palæontographical Society.

Davidson, Thomas. 1861. On British Carboniferous Brachiopoda. Geologist 4: 41–59.

Davidson, Thomas. 1862. On some Carboniferous brachiopods collected in India. Quarterly Journal of the Geological Society of London 18: 25–35.

Hall, James. 1860. Descriptions of new species of fossils from the Silurian rocks of Nova Scotia. Canadian Naturalist 5: 144–59.

Hutton, Frederick Wollaston. 1861. Some remarks on Mr Darwin’s theory. Geologist 4: 132–6, 183–8.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.

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."

Letter details

Letter no.
DCP-LETT-3135
From
Thomas Davidson
To
Charles Robert Darwin
Sent from
Brighton
Source of text
DAR 99: 1–2
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 3135,” accessed on 7 December 2019, https://www.darwinproject.ac.uk/letter/DCP-LETT-3135.xml

Also published in The Correspondence of Charles Darwin, vol. 9

letter