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Darwin Correspondence Project

From George Maw   30 June 1862

Benthall Hall | Broseley

30th. June 62

Dear Sir

Some time ago you asked me to send you specimens of the Pelargonium leaves I referred to in a former note as presenting a singular relation in their form to the characters of the respective flowers of the two varieties—1 of the enclosed, No 1 is a leaf of the original “Tom Thumb” No 2 of “Brilliant” which is a monstrous variety or rather condition of “Tom Thumb”   The symmetrical leaf of Tom Thumb is always as you are doubtless aware accompanied by a perfect and symmetrical truss of flowers but “Brilliant” with the deformed leaves very rarely perfects a good truss— The individual flowers are thin with a tendency to wither & petals reflexed. in fact the distortion of leaf is accompanied by a corresponding deformity in the flower.— As far as I have observed, this relation between leaf and flower holds good in all the cultivated varieties of the Scarlet Pelargonium   those with flat symmetrical leaves always have a good truss of flowers & those in which the leaf is much crumpled (as in “mountain-of-light” “Mrs Lennox” &c) the truss is poor & imperfect—2 I believe you consider these relationships between parts as evidence of their being modified forms of a common organ but do we not see similar phenomena in the relations of organs as to character, time of development, &c that cannot possibly be homologous   take as a familiar example the development of hair on the face at the time the generative organs are perfected3

If the relationship in character of leaf and flower in Pelargonium is from their being modified forms of a common organ—why not on the same principle assume that the generative organs & the hair on face are homologous? & on the supposition that the occasional leafy development of a petal is an instance of reversion to an original common organ. I think we might with equal justice assume that the Castration of male producing the contours & general aspect of female (in those races where the aspect of the sexes is notably distinct as in the ox tribe) as evidence of the sexes having been developed from an original a-sexual form, resembling the female— It is however very remarkable that the destruction of the generative organs in either Sex does not produce reversion to a common neuter form, but in many instances it causes the assumption of the special attributes of the opposite sex   for instance the castration of the bull produces in the ox the physical contours of the cow & many instances are recorded of the destruction of the ovary in hen birds producing cock plumage—the voice of the male & general physical aspect of male bird— The appearance of hair on the chin of old women is perhaps a parallel case   I cannot help thinking that these cases show how very much may depend on the mere relationship of parts, & that two organs may be subject to similar influences without their necessarily being homologous— with respect to the cotemporary phenomena at birth I noticed as presenting a difficult case for Natural Selection. I can understand it as perfectly logical that the several phenomena as the production of milk by the mother—the organization of heart—the altered Circulation—respiration of fetus on the cotemporary operation of which depends the life of the offspring, may be kept together at birth on the principle of Natural Selection but my difficulty is as to how these functions which would be useless either separately or in an imperfect state could be accumulated gradually because the offspring unless absolutely perfect in every one of these functions (with a perfected supply of milk from its mother) could not survive & accumulate & advance on their progenitors—

The perfect readyness with which you have discussed objections to your theory induces me to take the liberty of mentioning these difficulties that have occurred to me but pray do not feel under any obligation to reply as I know you must be overwhelmed with correspondence.

Believe me Dr Sir | yours truly | George Maw.

Charles Darwin Esqr

CD annotations

1.1 Some … imperfect— 1.14] crossed ink
1.12 leaves … perfected 1.18] ‘These remarks show he does not understand— case of Hair is correlation in period alone’ [‘I never suppose’ del] ‘It is rash to speak of correlation except when organs are homological.’ added in margin, ink
2.2 common … sexes 2.8] ‘Is this so. Ox? I think it is in some birds’ added in margin, ink
2.11 instances … women 2.15] scored brown crayon
Top of letter: ‘See his Review of me4 blue crayon
Cover: ‘G. Maw on correlation cases & difficulties’ ink, del brown crayon; ‘On castrated males & females not returning to neuter state, but to opposite state; as if must take on one or other state neuter state last’ ink; ‘Bears [on] Selection’ ink, underl brown crayon; ‘Ch VII’5 brown crayon, del brown crayon *S1 !alignleft!CD note:6 *S2 Why simultaneous? Young fish with yolk milk need not be selected till long after.— Mucus in marsupial Batrachians— diffused mammary glands in marsupial Ornithorhynchus.


CD cited Maw’s observations on this subject in Variation 2: 330–1.
CD had elaborated his views on the ‘correlation of parts’ in Origin, pp. 143–50, stating that ‘the whole organisation is so tied together during its growth and development, that when slight variations in any one part occur, and are accumulated through natural selection, other parts become modified’ (p. 143). In particular, he argued that ‘[t]he several parts of the body which are homologous, and which, at an early embryonic period, are alike, seem liable to vary in an allied manner’ (p. 143), asserting that these laws of correlation were thus responsible for ‘modifying important structures, independently of utility and, therefore, of natural selection’ (p. 144), and citing in evidence ‘a striking case of correlation’ in pelargoniums (p. 145). In his review of the third edition of Origin, Maw criticised CD’s views on this subject, arguing that such morphological relationships were perfectly consistent with special creation, and that there were cases of ‘correlation of organization’ in which genealogical affinity was ‘out of the question’, but in which it was ‘not unreasonable to suppose that the uniformity of model, upon which the more important parts are formed’ resulted from ‘special creation working out a consistent proportion of the integral parts’ (Maw 1861, p. 7587). CD and Maw had subsequently corresponded on this question (see Correspondence vol. 9, letters to George Maw, 19 July [1861] and 31 August [1861], and letter from George Maw, 27 August [1861]).
Maw 1861. See n. 3, above.
CD refers to chapter 7 of his ‘big book’ on species, entitled ‘Laws of variation: varieties and species compared’ (see Natural selection, pp. 275–338), which contained his original discussion of ‘Correlation of growth’. CD later addressed the subject of this chapter at greater length in Variation, chapters 24–6, including a revised discussion of ‘Correlated variability’ (Variation 1: 319–38; see also letter to George Maw, 3 July [1862] and n. 7).
The note is in DAR 99: 10. See also letter to George Maw, 3 July [1862].


Discusses cases of assumed correlation, e.g., facial hair and generative organs, sexual characters in castrated oxen. Finds it difficult to see how correlation of functions which would be useless separately can be accumulated gradually through natural selection.

Letter details

Letter no.
George Maw
Charles Robert Darwin
Sent from
Source of text
DAR 99: 5–9
Physical description
8pp †, CD note

Please cite as

Darwin Correspondence Project, “Letter no. 3629,” accessed on 20 August 2019,

Also published in The Correspondence of Charles Darwin, vol. 10