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Darwin Correspondence Project

To T. H. Huxley   29 [September 1855]1

Down Farnborough Kent


My dear Huxley

Your letter, as you may well suppose, has greatly interested me.2 Let me premise that I have often groaned over my want of elementary knowledge in microscopical structure, so that I could not recognise an incipient ovum. I could only make out, that at certain times in the gut-formed gland (after spirits) there were aggregations of matter in colour & aspect like the contents of the ovarian tubes.3 I cannot understand yet that I could have fancied that I saw what I call “pointed little balls with a large inner cell & this again with 2 or 3 included granules.”4 But do not think that I have the presumption to dispute what you say about the contents of the gut-formed glands.5 I could only ask whether you have examined specimens taken at very different periods: I remember well what a diversity of appearance these glands presented. Have you seen see P.S. them nearly empty with the walls studded with cells? Have you seen the pellets of yellow (after spirits) cellular matter apparently travelling down the ducts: these were so conspicuous, (though very rarely met with) that really I think no amount of blundering could have made me fancy them; for I removed the duct.— By the way I shd. have said that you give a perfectly correct account of what my idea was.—

Whatever the nature of the gut-formed glands may be; I cannot doubt from the many cases which I have seen, that you will find that the ovarian tubes with ova are directly continuous with them or rather with the duct leading from them:6 I remember one case of Conia (= Tetraclita), in which I laid them so open that Leonard the artist,7 drew them for me. On the other hand I cannot persuade myself for a second that they are cement-glands; though it is very certain (for I have seen it repeatedly) that in the pupal condition the cement-ducts run from the antennæ to these glands;8 on the other hand the branching out of this duct in the middle into the ovarian tubes in the very young cirripede seemed to me equally plain. That they are not cement glands, I must conclude from all my observations on the complicated apparatus in all the sessile cirripedes; in which at each period of growth new glands could be seen in process of formation.9

Again I really traced the cement duct in Conchoderma into the gland figured, Pl. IX fig 310 as plainly as the aorta into the heart.— Though I found the gland & dissected it out of the body in Conchoderma, Pollicipes, Scalpellum & Ibla, I never found it in Lepas; & I remember feeling considerable surprise at this: I will write no more; but I cannot conceive that I can have erred in (1st) so repeatedly tracing the branching ovarian tubes into the duct close to the gut-formed glands & (2d) & more especially in tracing the cement duct into the cement-gland.— If these points are false, I shall never trust myself again.11 That the gut-formed gland has some other relation to the ovarian tubes than what I imagined seems to follow from what you have seen;12 but I supplicate you to look at a few more full-grown specimens; but I wish it was not autumn.— The white deep-water ribbed Bal. porcatus you would find a good species.

Forgive the length of this letter. If you work at all more at cirripedes, do attend to circulatory system; it was quite beyond my tether.13 The open space under the skin between the scuta (ie on the ventral surface homologically!) seemed to me the great centre, & there are some desperately odd voluntary small superficial muscles looped one into other.—

Thank you much for writing to me. I have really no suggestions to offer, but I am delighted to hear how energetically you seem to be at work. I hope that your marriage will not make you idle: happiness, I fear is not good for work.

My dear Huxley | Most truly yours | C. Darwin

P.S. I have just remembered that I had one specimen preserved between glass. This I have just examined & broken up: it is in the state which I call “more or less globular or finger-shaped aggregations of pulpy matter”.14 But I can assure you I have often seen these organs presenting a wholly different appearance with cells. I could not in this specimen detect a single cell with included nuclei or granules (or whatever they might be called) & which I compared with drawings by (I think Steenstrup15 & which appeared to my ignorant eyes, exactly like ovigerms.—-


Dated from CD’s reference to Huxley’s recent marriage (21 July 1855) and by the reference to the season being autumn.
In the missing letter, Huxley had apparently discussed his recent examination of cirripede specimens, following up CD’s earlier request (see letter to T. H. Huxley, 13 September [1854]). Huxley and his wife had spent their honeymoon at Tenby, South Wales, where Huxley continued his occupations of the previous summer: gathering specimens of marine invertebrates and working on the proposed coastal survey (L. Huxley ed. 1900, 1: 130).
CD refers to the gut-formed gland in cirripedes that he described as the cement gland of the organism and that he believed was formed from a portion of the ovaria. He described the appearance of the contents of the gland in Living Cirripedia (1851): 34: ‘The gland contains a strongly coherent, pulpy, opaque, cellular mass, like that in the cement-ducts; but in some instances … this cellular mass becomes converted within either the ducts or gland, or within both, into transparent, yellow, tough cement.’
Living Cirripedia (1851): 57. CD traced the ovarian tubes from the peduncle up to two gut-formed masses that he believed to be the ‘true ovaria’. He stated that the appearance of the contents of these glandular masses varied much, but ‘so closely resembled, in general appearance and size, the ovigerms with their germinal vesicles and spots, which I have often seen at the first commencement of the formation of the ova in the ovarian tubes in the peduncle, that I cannot doubt that such is their nature.’ (Living Cirripedia (1851): 57–8).
Huxley’s description of the structure and contents of the gut-formed glands, published as one of his lectures on natural history, differed to some degree from that given by CD. In T. H. Huxley 1857, p. 230, he wrote: The “gut-formed glands” in Lepas are thick-walled slightly lobulated tubes, bent upon themselves, and composed of a structureless membrane provided with a very thick coating, which appeared structureless, or at most slightly granular, when quite unaltered; clear rounded vacuoles are however readily formed in it and the substance in their vicinity becomes granular, by the action of water. If the contents be squeezed out, a corresponding, but more marked change takes place; numerous clear vesicles are developed, and the surrounding substance becomes dark and granular, until at length they put on the appearance of a mass of clear cells with dark granular walls.
In his lecture on Cirripedia, Huxley gave tentative support to this, stating ‘my own dissections of Lepas, while they have not enabled me absolutely to trace these parts with one another, rather favouring the conclusion that they are thus connected.’ (T. H. Huxley 1857, p. 239).
Samuel William Leonard, a member of the Microscopical Society of London. For Leonard’s work for CD, see Correspondence vol. 3, letter to J. D. Hooker, [December 1846].
In the pedunculated barnacles, CD had traced the cement ducts to two small organs that he believed were the cement glands. He concluded (Living Cirripedia (1851): 35): the gland itself is a part of an ovarian tube specially modified; and further, that the cellular matter, which in the ovarian tubes serves for the development of the ova, is, by the special action of the walls of the gland, changed into the opaquer cellular matter in the ducts, and this again subsequently into that tissue or substance, which cements the Cirripede to its surface of attachment. In the sessile cirripedes, however, he could state only that ‘the tubes on which the cement-glands are formed, run into the mass of ovarian cæca’ (Living Cirripedia (1854): 134). He described in Balaninae how ‘at each period of growth, a pair of new cement-glands is developed, larger than those last formed, and making, with the older glands, a chain, connected together by what I have called the cement-trunk.’ (ibid., p. 134).
The Russian naturalist August David Krohn disputed CD’s observations on both of these points in 1859. An experienced dissector of marine invertebrates, Krohn traced the cement ducts up to a number of spherical grape-like bodies in the tissue surrounding the ovaries, which he held to be the cement glands. The parts of the cement ducts that CD thought were the cement glands Krohn stated were simply swellings where the cement collected before travelling down the tubes (Krohn 1859, p. 356). The branching tubes in the bottom of the mantle of Conchoderma aurita (a misspelling of C. auritum) that CD took for ovarian tubes, Krohn asserted were actually cement tubes (p. 358). This called into question CD’s observation of a direct connection between the ovaria and the cementing apparatus and thus also his hypothesis concerning the ‘evolution’ of the latter from the former. See Crisp 1983 for a comparison of CD’s interpretation of the female reproductive system with what is accepted today, and a discussion of how CD’s evolutionary views led him to confuse the cement glands and ovaries.
Huxley stated he could ‘never find anything resembling a true ovum’ in the gut-formed glands and concluded that they were rather ‘accessory glands, analogous in function to those which secrete the walls of the ovisac in the Copepoda.’ (T. H. Huxley 1857, p. 239).
CD gave only a cursory description of the circulatory system of pedunculated and sessile cirripedes (Living Cirripedia (1851): 46 and Living Cirripedia (1854): 87).
Living Cirripedia (1851): 57. The specimen may have been of Conchoderma aurita since much of CD’s description of the female organs of the Lepadidae was drawn from an examination of this species (ibid., pp. 56–8).


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Crisp, Dennis J. 1983. Extending Darwin’s investigations on the barnacle life-history. Biological Journal of the Linnean Society 20: 73–83.

Krohn, August David. 1859. Beobachtungen über den Cementapparat und die weiblichen Zeugungsorgane einiger Cirripedien. Archiv für Naturgeschichte 25 (pt 1): 355–64.

Living Cirripedia (1851): A monograph of the sub-class Cirripedia, with figures of all the species. The Lepadidæ; or, pedunculated cirripedes. By Charles Darwin. London: Ray Society. 1851.

Living Cirripedia (1854): A monograph of the sub-class Cirripedia, with figures of all the species. The Balanidæ (or sessile cirripedes); the Verrucidæ, etc. By Charles Darwin. London: Ray Society. 1854.

Steenstrup, Johannes Japetus Smith. 1846. Untersuchungen über das Vorkommen des Hermaphroditismus in der Natur. Ein naturhistorischer Versuch. Translated from the Danish by Dr C. F. Hornschuch. Greifswald.


Responds to THH’s questioning of his observations on cirripede anatomy with extensive discussion of what he observed. Admits his elementary knowledge of microscopical structures but seriously doubts he has erred. Cement glands, ovarian tubes, etc.

Letter details

Letter no.
Charles Robert Darwin
Thomas Henry Huxley
Sent from
Source of text
Imperial College of Science, Technology and Medicine Archives (Huxley 5: 21); Janet Huxley (private collection)
Physical description
ALS 5pp

Please cite as

Darwin Correspondence Project, “Letter no. 1757,” accessed on 25 September 2023,

Also published in The Correspondence of Charles Darwin, vol. 5