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Darwin Correspondence Project

To George Maw   3 July [1862]1

Down Bromley Kent

July 3d

Dear Sir

Your criticisms are profoundly interesting to me.2 A downright good objection or difficulty is very nearly as interesting as a favourable fact.— Your Review always struck me as very able (though I am not now quite so much shaken by some remarks as I was at first)3 & I have given some few of your objections in a new German edition.4 Very sincere thanks for the Pelargonium leaves.5 I shd. certainly rank this as a case of true correlation; because the parts are homologous & it seems to me inherently probable that parts, which are quite alike in an early stage of development on the same individual would be apt to be similarly affected by the unknown causes of variation. If you will look at my discussion in Ch. V. Origin (p. 162–164 3d. Edit) you will see that I expressly guard against the assumption that parts going together throughout whole classes are necessarily correlated.6 But I now see that I ought more plainly to have said that “correlation of growth” contains a most heterogenious set of facts.7 If you had asked me yesterday about hair & sexes, I shd. have said that it was only a case correlation so far as that the Hairy character had become attached to the male sex, in the same accidental (to speak loosely) manner in which large wattles have become correlated with male Carrier pigeons.— But your remarks show me that there is something more. I shd. hardly have said that the ox was quite like a cow; or an old woman like a man; but I think I have read of female birds quite like males in their plumage, & the case seems very strange & inexplicable. I must remember & attend to this; but the subject is far too large for me.—8 I cannot help looking confidently to all vertebrata as having descended from an Hermaphrodite form; (though only one hermaphrodite genus still exists) & that males & in lesser degree females have acquired new characters in “correlation” (to use my favourite term) or in “accidental correlation” with sex.9 But a man must be a fool to hope even to conjecture (supposing for the moment that my views are in the main correct) how all the wondrous changes have been effected. I had not forgotten your good case of coadapted structure at or before birth.10 I do not quite see necessity of such close simultaneous development as you do. Some Young fish are born with bag of yolk, & this might last long till milk was secreted. Those young Batrachians which are hatched in a quasi marsupial pouch on mothers back are believed to feed on mucus secreted by whole surface; concentration of glands would make a mamma, & in the Ornithorhynchus (marsupial order) the mammary glands are still diffused. But this is all conjectural rubbish. Pray however (I must add) reflect on the quasi-placenta in cartilaginous fishes.

I have lately published a small Book on Orchids (small portions of which alone bear on the general question of Species) parts of which I think would interest you. I cannot conceive how I forgot your name when I made out a list of copies to send away.—11 As I hope you will permit me to send you a copy, I will today write to my publisher.—12 I shd. be much pleased, if any criticisms occur to you, to hear them, or read them if ever you review semi-botanical works.—

I assure you that I feel most sincerely grateful for your remarks & for the very kind manner in which you make them.—

Pray believe me | My dear Sir | Yours sincerely | C. Darwin


The year is established by the relationship to the letter from George Maw, 30 June 1862.
See letter from George Maw, 30 June 1862.
Maw 1861. For CD’s reaction to Maw’s review of Origin, see Correspondence vol. 9, letters to George Maw, 13 July [1861] and 19 July [1861].
In Bronn trans. 1863, p. 445, CD added a reference to Maw’s objection to his statement that ‘the grand fact in natural history of the subordination of group under group’ was explained by the theory of descent from a common ancestor and of divergence. See letter to H. G. Bronn, 25 April [1862] and Correspondence vol. 10, Appendix VIII.
See letter from George Maw, 30 June 1862.
The section to which CD refers, headed ‘Correlation of growth’ (Origin 3d ed., pp. 161–4), concludes: We may often falsely attribute to correlation of growth structures which are common to whole groups of species, and which in truth are simply due to inheritance; for an ancient progenitor may have acquired through natural selection some one modification in structure, and, after thousands of generations, some other and independent modification; and these two modifications, having been transmitted to a whole group of descendents with diverse habits, would naturally be thought to be correlated in some necessary manner.
At the start of his discussion in the third edition of Origin (p. 161), CD stated: ‘This is a very important subject, most imperfectly understood’; in the fourth edition he added: ‘and no doubt totally different classes of facts may be here easily confounded together: we shall presently see that simple inheritance often gives the false appearance of correlation’ (Origin 4th ed., p. 170). CD gave a more detailed discussion of this subject in Variation 2: 319–38, under the heading ‘correlated variability’; he noted that he had formerly used ‘the somewhat vague expression of correlation of growth, which may be applied to many classes of facts’, and sought to distinguish ‘correlated variability’ from what in this letter he calls ‘accidental correlation’. See also letter from George Maw, 30 June 1862 and n. 5.
In the chapter on reversion in Variation, CD included a discussion of what he called ‘latent characters’, the ‘most obvious illustration’ of which, he claimed, was ‘afforded by secondary sexual characters’ (Variation 2: 51). He then stated: It is well known that a large number of female birds … when old or diseased, or when operated on, partly assume the secondary male characters of their species … On the other hand, with male animals, it is notorious that the secondary sexual characters are more or less completely lost when they are subjected to castration … But characters properly confined to the female are likewise acquired … We thus see that in many, probably in all cases, the secondary characters of each sex lie dormant or latent in the opposite sex, ready to be evolved under peculiar circumstances.
CD discussed the origin of the sexes in vertebrates in Descent 1: 207–11, arguing that ‘some extremely remote progenitor of the whole vertebrate kingdom appears to have been hermaphrodite or androgynous’. He also thought it ‘quite possible’ that as each sex ‘gradually acquired the necessary organs proper to it, some of the successive steps or modifications were transmitted to the opposite sex’, and he presented ‘innumerable instances of this form of transmission’ (p. 208).
See letter from George Maw, 30 June 1862, and Correspondence vol. 9, letter from George Maw, 27 August [1861].
Maw’s name is included on the presentation list for Orchids (see Correspondence vol. 10, Appendix IV); it was probably added as an afterthought.
The letter to John Murray has not been found.


Thinks GM’s Pelargonium is a case of true correlated characters. Feels secondary sexual characters are only accidental correlations; does not see the same necessity for close simultaneous development of certain characters as GM does.

Will forward a copy of his Orchids.

Letter details

Letter no.
Darwin, C. R.
Maw, George
Sent from
Source of text
Royal Horticultural Society
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 3640,” accessed on 20 January 2017,