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Darwin Correspondence Project

From Hewett Cottrell Watson   [3? January 1860]1

Notes on Darwin’s ‘Origin of Species2

1. Admitted the probability of a gradual ‘variation’ from parent to progeny, from ancestors to descendants, to an unlimited extent, if traced through a vast series of successions.3

2. Also, that among the countless numbers of organic beings produced, a process of ‘natural selection’ will in the long run determine which kinds shall die out, and which shall continue to produce descendants, themselves in turn more or less changing still.

3. Also, that a constant divergence from the lineal types is thus effected; because variation is necessarily divergence, and because no extremely antient type appears to have been exactly continued to the present epoch.

4. Such divergence nepotally onwards necessarily implies an equal convergence ancestrally backwards; which must therefore be admitted, although unproved except for slight variations and brief periods.

5. Constant convergence backwards must lead at length to one single prototype;—which itself must have been originated in some mode different from the mode in which all its successors have been produced; because that prototype could have had no organic parent.

6. Constant convergence onwards from that prototype must have led successively to types,—

diag here

We may assume the million to represent the number of specific or quasi-specific types now existing on the Earth.

7. Are we now at or near the end of the divergent variations? It would seem not. No grounds are shown for supposing that variation from parent to progeny has ceased, or that it is slower or less complete than heretofore. And the theory of the ‘Origin’ proceeds on an assumption that present facts evidence a continuance of variation now as in eras past.

8. Therefore this figure of 1,000,000 may and will, for aught we can see to the contrary, go on indefinitely increasing until the Earth has its present million increased to millions

diag here

&c. &c. &c.

9. Eventually, in this course, there will be as many millions of species as of beings or pairs of beings; every one or pair still tending to vary. If it be argued that ‘natural selection’ will prevent this vast increase of specific types, at any one time in existence, the answer is, why did it not arrest them at 10,000 or 100,000?— Why now, rather than then?— Or, why at 2 millions rather than at 4 millions?—&c. &c.

10. Thus, whether we go ancestrally backwards, to arrive at one prototype, not produced like all the rest that have succeeded it;—or go nepotally diverging onwards to a termination in countless million of species,—in either course we arrive at something so totally different from what is now observed, so utterly incapable of proof, so inconceivable as a reality, that it must seem in itself an improbability amounting to an absurdity almost.

11. Ought we not to seek carefully among present facts or events for some counter-action in nature, adequate to save us from being forced upon this almost reductio ad absurdum in either direction, either backwards or forwards?— I think that the counter-action can be seen and specified.

12. Would it not be better to reason up to no beginning, and to no end, than thus to make out a seeming absurdity, by arriving at results totally different from, if not absolutely inconsistent with, the present course of natural events, as seen in our own small span of time?4

13. It would appear that the difficulty could be met and neutralized by the hypothesis or inference that individuals converge into orders, genera, species, as well as diverge into species, genera, orders, through nepotal descent.

14. No doubt that hypothesis (rejected in the ‘Origin’) is far more difficult to support by evidence. But various facts in nature seem explicable only on this assumption. And it tends to remove other difficulties which might be urged against the theory of the ‘Origin’, and which nepotal divergence by itself seems unequal to explain;—for example, the intricately complex manner in which characters are crossed and combined in species; the effect of which would likely be to throw the same species into different groups, not subordinate to each other, if classification were attempted on the hypothesis, that any character in common between two species must have been derived from some common ancestor.

CD annotations

0.1 Notes … Species] ‘by H. C. Watson’ added ink
3.1 Also … epoch. 3.3] ‘I see this is common opinion & was mine but I have come to doubt. To my mind at the time, the cause of divergence was an important step.’ added ink over pencil
4.1 Such … periods. 4.3] ‘I do not see why variations should not fluctuate backwards & forwards, without much Divergence.’ added ink
8.1 Therefore … &c. 8.4] ‘I think I can show that this is not so.—’ added pencil, del pencil
9.1 Eventually … &c. &c. 9.6] ‘C. of Good Hope.’ added pencil, del pencil
12.1 Would … ancestor. 14.9] ‘Ch 65 added brown crayon; ‘I daresay this has taken place to small extent; it is when “adaptive” characters affect closely related forms.—’added ink

CD note:6

Species which are rare (& all wd become rare if infinitely many species) will be very liable to extermination. Moreover I fully believe that rare species, (from fewness of individuals & therefore less chance of profitable variations) will vary less quickly,— *(possibly close interbreeding would come into play with very rare species: mem. decrease in size in Auroch, Red Deer &c.) [interl] so that the great increase of number of species would act as a sort of regulator to further increase. Moreover Physical conditions are not infinitely different in kind, & as far as adaptations to physical conditions are concerned the number of species would soon come to a limit. But I fully, most fully admit, that the organic [interl] relations will tend, with increase of number of species, to go on getting more & more complex, & thus there will be tendency to increase in number of new species. Then will come in checks above alluded to. We do not know the full number anywhere arrived at.— mem. naturalised plants at C. of Good Hope.— Also dominant invading species will destroy many representative species: Mem. Hooker on Australia.—7 ink and pencil, del pencil


The date is suggested by CD’s remark in his letter to Charles Lyell, 4 [January 1860], that he had received a long letter from Watson.
The accompanying letter from Watson, alluded to in the letter to Charles Lyell, 4 [January 1860], has not been found.
Watson responded enthusiastically to Origin (see Correspondence vol. 7, letter from H. C. Watson, 21 November [1859]). In 1845, Watson had publicly announced his own belief in the transmutation of species (Watson 1845), and he again discussed the subject in the final volume of Watson 1847–59. CD had read this volume on publication (see Correspondence vol. 7, letter to J. D. Hooker, [26 May 1859]).
This and the following two paragraphs were marked ‘Ch 6’ by CD (see CD annotations). He refers to chapter 6 of Origin, ‘Difficulties on theory’ (Origin, pp. 171–206). CD later responded to Watson’s notion of a convergence of species in the third edition of Origin, using the arguments set out in the annotations to this letter (Origin 3d ed., pp. 141–3; Peckham ed. 1959, pp. 267–70). He concluded that there must be limits to the ‘tendency to an indefinite augmentation of specific forms’ (Origin 3d ed., p. 143). See also letter to H. C. Watson, [5–12 January 1860].
See n. 4, above.
The note was begun at the top of paragraph 9 and continued on the verso of Watson’s letter. See also letter to H. C. Watson, [5–12 January 1860].
CD had just finished reading Hooker 1859, in which Joseph Dalton Hooker discussed the invasion of Australia by Indian plant species (see preceding letter).


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Origin 3d ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 3d edition, with additions and corrections. By Charles Darwin. London: John Murray. 1861.

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.

Watson, Hewett Cottrell. 1845. On the theory of "progressive development," applied in explanation of the origin and transmutation of species. Phytologist 2: 108–13, 140–7, 161–8, 225–8.

Watson, Hewett Cottrell. 1847–59. Cybele Britannica; or British plants and their geographical relations. 4 vols. London: Longman.


Notes by HCW on the Origin dealing especially with divergence and convergence. Believes there is some natural tendency to converge into groups in opposition to divergence generated by natural selection.

Letter details

Letter no.
Hewett Cottrell Watson
Charles Robert Darwin
Sent from
Source of text
DAR 47: 135–8
Physical description
Amem 4pp ††

Please cite as

Darwin Correspondence Project, “Letter no. 2636,” accessed on 21 January 2022,

Also published in The Correspondence of Charles Darwin, vol. 8