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Darwin Correspondence Project

From J. D. Hooker   [11 May – 3 December 1860]1

reducing individuals here & destroying genera elsewhere— Whether man reduces the bulk of organic & increases that of inorganic matter or no there cannot be a doubt that his influence is devoted to reducing existing species & hence improving our means of classification, which is only another expression for, further sundering allied forms—2 The number of new varieties he creates are as nothing to the destruction of old & the reduction of the battle field for the remainder.— the struggle is hence all the harder in the space he leaves to native vegetation.3 Man & his intellect are all part of the scheme & must not be shirked. Still the question makes me giddy from its complication.

I think little of his objection on the score of varieties of the lineal descendent of A. becoming confounded with those of 〈B〉4   no doubt such cases occu〈r〉   I have somewhere I think alluded to them as very probably frequent. 〈I should〉 now put into this category all those anomalous plants which hover between two otherwise very remote species in genera or families.5 It struck me that such cases were well explained by your divergent series—6 Such cases if decided ones should be rare— so they are— There is however the perpetual difficulty of deciding between reversion of character & persistence of character. Let us suppose that Dicots. were developed through & after Monocots, & regard Conifers as anomalous Dicots nodding towards Cryptogams & we have a case in point,— the Conifers are either Dicots that vary towards Cryptogs. or (as I should incline to suppose) a sub series of Dicots. developed parallely to the main Monocot branch, but in which alone 〈    〉 the Cryptog. characters persisted 7   Watson must think that subsequent variation may as easily be towards8 the old type as away from it— this is conceivable of course, but I maintain it is not so in nature— it is opposed to my idea of centrifugal variation.—9 Now variation is not centrifugal because of any repulsive or repellent power, but simply because in fact it is a million chances to one that identity of form once lost will be returned to.10 Each character we estimate is a compound of lesser characters each too minute to estimate in the gross, but missed if with-drawn. A petal if further varying after it has once varied has a thousand characters of form color consistence nervation &c &c &c to chuse amongst (so to speak) besides those its grandparents bore. After all, experience is our best guide, & we do not find in the human race any reversion so strong as would lead us to confound a man with his ancestor, a Yankee with an Englishman— Whoever saw a Grandfathers portrait that would really pass for his Grandsons—& if we do not find reversion amongst individuals so close in kin & in time, how can we expect them in organisms that have reached the specific term of divergent development—

True you may have a 10th removed lineal descendent (who supposing the name of Wedgwood to be lost to genealogists—except by a stray portrait) may so resemble the Wedgwood portrait that an Ethnologist would call him an anomalous Darwin representing the lost Wedgwood type.—but the chances are a hundred to one in favor of both Wedgwood & Darwin physiognomy being wiped out long before the 10th. generation—11 How often do we consider 2 people strikingly alike till we see them together & then consider them wholly unlike; this is because one minute character common to both was alone carried away, in the mind, but which, though no doubt present, is not perceived when again sought for amongst the thousand other characters of the 2 faces.

CD annotations

1.1 reducing individuals … frequent. 2.3] crossed brown crayon
2.3 now put … they are— 2.8] scored brown crayon
2.7 There is … persisted 2.13] ‘11.12 brown crayon, circled brown crayon
2.7 There is … with-drawn. 2.16] crossed brown crayon
2.22 & we … Grandsons. 2.25] scored brown crayon
2.25 & if … faces. 3.10] crossed brown crayon

Footnotes

The date range is established by the relationship between this letter, the letter from H. C. Watson, 10 May 1860 (Correspondence vol. 8), and the letter to J. D. Hooker, 4 December [1860] (ibid.).
Hooker advocated uniting species in classification: ‘It is strange that local naturalists cannot see that the discovery of a form uniting two others they had previously thought distinct, is much more important than that of a totally new species, inasmuch as the correction of an error is a greater boon to science than is a step in advance’ (Hooker and Thomson 1855, p. 36). For further information on the ‘splitting’ and ‘lumping’ schools in taxonomy, their effect on the number of species, and the involvement of Hooker and Hewett Cottrell Watson in the debates, see, for example, the letter to J. D. Hooker, 17 April [1865] and n. 12.
According to Hooker, human activity represented ‘a new enemy to scarce old forms [of plant], and a strong ally to those already common’; he recorded the destruction of local genera in Australia, New Zealand, and South Africa in the wake of human activity (Hooker 1859, pp. civ–cv).
Hooker apparently refers to Watson’s hypothesis that variation could cause the descendants of two different plants ultimately to become morphologically indistinguishable (see Correspondence vol. 8, letter from H. C. Watson, 10 May 1860). CD had earlier communicated Watson’s arguments in favour of ‘convergence’ to Charles Lyell and Hooker (ibid., letter to T. H. Huxley, 11 January [1860] and n. 5). These were contained in the letter from H. C. Watson, [3? January 1860] (ibid.), and included Watson’s view that his principle of ‘convergence’ explained the occurrence of characters in common between two species where CD’s theory of divergence did not. CD discussed Watson’s views and the idea of ‘convergence’ in the revised American edition of Origin (Origin US ed., pp. 116–17**; see Correspondence vol. 8, Appendix IV, pp. 576–7) and in Origin 3d ed., p. 141 (see n. 6, below).
Hooker’s interest in plants that were difficult to classify owing to their similarity to widely differing taxa is exemplified by his research on the anomalous Welwitschia mirabilis (Hooker 1863).
CD, with the aid of a diagram, discussed the operation of his principle of divergence on the species of a large genus in Origin, pp. 111–26. CD addressed Watson’s objection directly in a new passage added to Origin 3d ed., p. 141: I will only say that if two species of two closely allied genera produced a number of new and divergent species, I can believe that these new forms might sometimes approach each other so closely that they would for convenience sake be classed in the same new genus, and thus two genera would converge into one; but from the strength of the principle of inheritance, it seems hardly credible that the two groups of new species would not at least form two sections of the supposed new single genus.
For a summary of the main divisions of the contemporary classification of the vegetable kingdom, see Correspondence vol. 7, letter from J. D. Hooker, [9 March 1859]. In contrast to the prevailing view, Hooker maintained that conifers were advanced dicotyledons that retained some cryptogamic characters (see, for example, Correspondence vol. 7, letter from J. D. Hooker, [26 December 1858] and n. 3).
The letter text from this point was previously published in Correspondence vol. 10, as the letter from J. D. Hooker, [after 26 March 1862?]. It appears here with new footnotes.
Watson’s view of transmutation included both centrifugal variation and centripetal variation (the former generating divergence and the latter what Watson called convergence). See Correspondence vol. 8, letter from H. C. Watson, [3? January 1860]. See also this volume, Supplement, letter from H. C. Watson to J. D. Hooker, 4 January 1861 and n. 9, and Correspondence vol. 9, letter to J. D. Hooker, 15 January [1861].
Hooker had introduced CD to his ideas of centrifugal and centripetal forces of variation in Correspondence vol. 3, letter from J. D. Hooker, 1 February 1846; the terms also occur in Hooker 1844–7, p. 315. CD had criticised Hooker’s use of the word ‘force’ and warned that ‘centrifugal’ variation implied a single centre (Correspondence vol. 3, letter to J. D. Hooker, [16 April 1846]).
Hooker may have been aware of the Wedgwood family joke that the Darwins were ‘more Wedgwood than the Wedgwoods’, since CD was the son of Susannah Wedgwood, and had married his cousin, Emma Wedgwood (B. Wedgwood and Wedgwood 1980, p. 269).
The annotation probably refers to the numbered portfolio in which CD kept his notes on divergence (see the 1932 catalogue of CD’s papers, DAR 220: 13). A quantity of notes marked ‘11’ are now collected in the Darwin Archive–CUL (DAR 205.5).

Summary

CD’s divergent series explains those anomalous plants that hover between what would otherwise be two species in a genus.

Inclined to see conifers as a sub-series of dicotyledons that developed in parallel to monocotyledons, but retained cryptogamic characters.

Mentions H. C. Watson’s view of variations.

Man has destroyed more species than he has created varieties.

Variations are centrifugal because the chances are a million to one that identity of form once lost will return.

In the human race, we find no reversion "that would lead us to confound a man with his ancestors".

Letter details

Letter no.
DCP-LETT-3036
From
Joseph Dalton Hooker
To
Charles Robert Darwin
Sent from
unstated
Source of text
DAR 205.5: 217 (Letters), DAR 47: 214
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 3036,” accessed on 13 November 2019, https://www.darwinproject.ac.uk/letter/DCP-LETT-3036.xml

Also published in The Correspondence of Charles Darwin, vol. 13 (Supplement)

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