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Darwin Correspondence Project

From C. F. Claus1   24 January 1869

Marburg

24/1 1869

Hochgeehrter Herr!

Indem ich mir erlaube, Ihnen beifolgende kleine Arbeit über die Fortpflanzungsweise von Leptodera 2 ehrerbietigst zu übersenden, darf ich wohl gleichzeitig mir die Freiheit nehmen, einige Zeilen an Sie zu richten und einem schon längst von mir gehegten Wunsche zu entsprechen, meine innige Hochachtung und Verehrung Ihnen auszudrücken. Sie werden, hochverehrter Herr, wohl wissen, dass unter den deutschen Zoologen zahlreiche Bewunderer und Anhänger Ihrer Selectionstheorie bemüht sind, nach Thatsachen zu forschen, die noch weitere Stützen für die Transmutation der Arten liefern, ohne die uns der Zusammenhang der organischen Lebenserscheinungen ein Räthsel bleibt. Ich selbst zähle mich auch zu jenen, ohne freilich wie Haeckel, dessen Werke Sie sicher trotz zahlreicher trefflicher und anregender Ideen mit mir als einen nicht reifen, zu enthusiastischen Versuch zu einer Naturphilosophie bezeichnen werden, die Nothwendigkeit überzeugender Beweismittel aus dem Auge zu verlieren.3 Gerade in diesem Winter beschäftigt mich der Gegenstand besonders, und ich bin durch eine öffentliche Vorlesung, die ich vor einem ansehnlichen Auditorium von Studirenden halte (“Darlegung und Kritik der Darwinschen Lehre”) gezwungen, das Material möglichst sorgfaltig durchzuarbeiten und auf Beweiskraft zu prüfen. Dabei ist es mir leider zur Klarheit geworden, dass H. nicht mit der nothigen Schärfe scheidet und überall seinen Glaubensausdruck für Beweis hält. Dem Wagnerschen Migrationsgesetz, das ja in Ihren Werken bereits vollkommen enthalten ist, kann ich unmöglich den ausschliessenden Werth, den der Verfasser beansprucht, zusprechen,4 offenbar hat er Ihre Lehre gar nicht ausreichend verstanden und den Einfluss der mittelbaren potentiellen Anpassung bei der natürl-Züchtung nicht entsprechend gewürdigt. Es ist möglich, dass ich den Inhalt meiner Vorlesungen als Versuch zu einer Prüfung der Beweismittel Ihrer Lehre in einer kleinen Broschüre veröffentliche. Doch will ich hiermit vorsichtig sein, den Gegenstand noch mehrmals zum Vortrag bringen und vorläufig lieber Anderen überlassen, die Häckelschen Selbsttäuschungen zu zurückzuweisen.5 Vorläufig bin ich mit einer Publication eines anderen Gegenstandes beschäftigt, von dem ich denken sollte, dass Sie vielleicht meinen Beobachtungen darüber einiges Interesse schenken, “Die Entwicklung der Lepaden”.6 Auch hier ist es ja Ihr Werk, welches die Grundlage bildet, wie es aber keinen Gegenstand gibt, der nicht nach Jahren von Neuem erfasst, eine weitere Fortführung—selbst nach der ausgezeichnetsten früheren Bearbeitung—ermöglichte, so auch hier. Zwar ist bereits von Pagenstecher ein Versuch gemacht, aber leider nicht mit der ausreichenden Sorgfalt und Gründlichkeit, die um Ihre Angaben zu erweitern nothwendig ist.7

Nun möchte ich mit der kleinen Untersuchung nicht eher abschliessen, als ich die Gewissheit habe, das mir zu Gebote stehende Material nicht vergrössern zu können. Sollten Sie verehrter Herr im Stande und Willens sein, mir einiges Material von Puppen8 und jungen in den Puppen steckenden Lepaden oder aus Balaniden recht bald mitzutheilen, so würde ich Ihnen zu grossem Danke verpflichtet sein. Insbesondere läge mir viel daran, die Puppen von Proteolepas, Ibla Cryptophialus Alcippe wie überhaupt diese sonderbaren Formen und deren Complemental males untersuchen zu können.9

Indem ich Sie bitte, meinen Wunsch nicht für zu unbescheiden halten zu wollen sondern nach Massgabe des Bestrebens eines naturae curiosi10 gütigst zu entschuldigen, zeichne ich als Ihr | hochachtungsvoll ergebener | C Claus | Professor der Zoologie

Footnotes

For a translation of this letter, see Correspondence vol. 17, Appendix I.
Claus enclosed an offprint of an article on the organisation and reproduction of the nematode Leptodera appendiculata (Claus 1868a). CD’s copy is in the Darwin Pamphlet Collection–CUL.
Claus refers to Ernst Haeckel. For more on Claus’s objections to Haeckel’s version of Darwinism, see Nyhart 1995, pp. 186–93.
Claus refers to Moritz Wagner and the ‘law of migration’ elucidated in Wagner 1868a and 1868b. In a letter to August Weismann of 22 October 1868 (Correspondence vol. 16), CD had remarked that Wagner greatly overrated the necessity for emigration and isolation. In Origin 5th ed., p. 120, CD referred to Wagner’s essay, noting that while geographical isolation was important for preventing crosses between new varieties, it was not necessary for the formation of new species.
Claus never published the lectures on Darwinian theory; but in later work he was highly critical of many aspects of Haeckel’s work, most notably the latter’s gastraea theory (see Claus 1874 and Claus 1876; see also Di Gregorio 2005, pp. 297–301).
Claus enclosed an offprint of an article on the cypris-like larvae of cirripedes and their transformation into sedentary adults (Claus 1868b). The offprint is in the Darwin Pamphlet Collection–CUL, and is lightly annotated.
Claus refers to Heinrich Alexander Pagenstecher and Pagenstecher 1863.
Claus followed CD’s usage in referring to the last larval stage in barnacles as ‘pupal’ (see Living Cirripedia (1854), p. 13); this stage is now more commonly referred to as the cypris stage (see Living Cirripedia (1851), p. 14).
The genus Alcippe is now Trypetesa. Proteolepas is no longer classed as a cirripede but instead is classed as a parasitic isopod of the family Cabiropidae (see Living Cirripedia (1854), p. 588). Claus refers to CD’s discovery of ‘complemental males’ in several species of Cirripedia. CD had observed minute males attached to the bodies of hermaphrodites, and differing greatly from them in size and structure (see Living Cirripedia (1851), pp. 231–2 and 281–93, Living Cirripedia (1854), pp. 23–30, and Newman 1993, pp. 377–81). In his letter to J. D. Hooker, 10 May 1848 (Correspondence vol. 4), CD remarked that the discovery was suggestive of the development of separate sexes, and thus of significance for his theory of species (see also Correspondence vol. 4, Appendix II, pp. 399–400). CD later suggested that complemental males might have developed in cirripedes to enable intercrossing between two hermaphrodites (see ‘On the males and complemental males of certain cirripedes, and on rudimentary structures’, Nature 8 (1873): 431–2; Collected papers 2: 177–82).
Naturae curiosi: inquirer into nature (Latin).

Bibliography

Claus, Carl Friedrich. 1874. Die Typenlehre und E. Haeckels sog. Gastraea-Theorie. Vienna: Manz.

Collected papers: The collected papers of Charles Darwin. Edited by Paul H. Barrett. 2 vols. Chicago and London: University of Chicago Press. 1977.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

Di Gregorio, Mario A. 2005. From here to eternity: Ernst Haeckel and scientific faith. Göttingen: Vandenhoeck & Ruprecht.

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.

Newman, William A. 1993. Darwin and cirripedology. History of Carcinology. Crustacean Issues 8: 349–434.

Nyhart, Lynn K. 1995. Biology takes form. Animal morphology and the German universities, 1800–1900. Chicago and London: University of Chicago Press.

Origin 5th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 5th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1869.

Translation

From C. F. Claus1   24 January 1869

Marburg

24/1 1869

Dear Sir!

While I venture to send you, most respectfully, the enclosed pamphlet on the reproduction of Leptodera2 I would also like to take the liberty of addressing a few lines to you and thereby to fulfil a wish that I have long held, that is, to express my sincere respect and admiration for you. You will no doubt know, most esteemed Sir, that among German zoologists there are numerous admirers and adherents of your theory of selection who are busy searching for facts that will provide further evidence for the transmutation of species, without which the relations of the phenomena of organic life will remain a mystery to us. I also count myself among them, though without losing sight of the necessity of producing convincing proof, unlike Haeckel, whose works you will surely agree are, in spite of numerous excellent and stimulating ideas, a not mature, too enthusiastic attempt at natural philosophy.3 Just this winter, I have been particularly occupied with this topic, and as I am giving a course of public lectures to a sizeable audience of students (“Explanation and critique of the Darwinian theory”), I've been forced to work through the material as carefully as possible and examine its persuasive force. While doing this it has unfortunately become clear to me that H. fails to analyse with sufficient rigour, and always treats his expression of belief as proof. I am unable to grant Wagner's law of migration, which indeed is already contained in full in your work, the exclusive importance that its author claims for it;4 clearly he has not adequately understood your theory, and accordingly has failed to appreciate the influence of indirect potential adaptation within natural selection. It is possible that I might publish the contents of my lectures in a small brochure, as an attempt at an evaluation of the evidence for your theory. However, I want to be cautious in this, to present the subject in lectures for a number of times yet, and preferably to leave it to others, for the time being, to refute Haeckel's self-deceptions.5 For the present I am occupied with a publication on another subject, “The development of the Lepadidae”, about which perhaps my observations might hold some interest for you.6 Here too it is your work that forms the foundation of the subject, but as there is no topic that is not taken up again after a number of years, where further advancement—even after a most excellent earlier treatment—would not be possible, so it is the case here. To be sure, Pagenstecher has already made such an attempt, but unfortunately not with the care and thoroughness that is necessary to further yourwork.7

Now, I would not be able to finish my little investigation unless I was sure that I could not add to the material at my disposal. If you, dear sir, should be able and willing to send me rather soon some specimens of pupae,8 and young Lepadidae still in their pupal stage or of Balanidae, I would be deeply grateful to you. It would be of special interest for me to be able to study the pupae of Proteolepas, Ibla Cryptophialus Alcippe, at the very least these peculiar forms and their complemental males.9 Hoping you will not deem my request too immoderate, but will kindly excuse it as the desire of a naturae curiosi,10 I remain | respectfully yours | C. Claus | professor of zoology.

Footnotes

For a transcription of this letter in its original German, see pp. 40–1.
Claus enclosed an offprint of an article on the organisation and reproduction of the nematode Leptodera appendiculata (Claus 1868a). CD’s copy is in the Darwin Pamphlet Collection–CUL.
Claus refers to Ernst Haeckel. For more on Claus’s objections to Haeckel’s version of Darwinism, see Nyhart 1995, pp. 186–93.
Claus refers to Ernst Haeckel. For more on Claus’s objections to Haeckel’s version of Darwinism, see Nyhart 1995, pp. 186–93.
Claus never published the lectures on Darwinian theory; but in later work he was highly critical of many aspects of Haeckel’s work, most notably the latter’s gastraea theory (see Claus 1874 and Claus 1876; see also Di Gregorio 2005, pp. 297–301).
Claus enclosed an offprint of an article on the cypris-like larvae of cirripedes and their transformation into sedentary adults (Claus 1868b). The offprint is in the Darwin Pamphlet Collection–CUL, and is lightly annotated.
Claus refers to Heinrich Alexander Pagenstecher and Pagenstecher 1863.
Claus followed CD’s usage in referring to the last larval stage in barnacles as ‘pupal’ (see Living Cirripedia (1854), p. 13); this stage is now more commonly referred to as the cypris stage (see Living Cirripedia (1851), p. 14).
The genus Alcippe is now Trypetesa. Proteolepas is no longer classed as a cirripede but instead is classed as a parasitic isopod of the family Cabiropidae (see Living Cirripedia (1854), p. 588). Claus refers to CD’s discovery of ‘complemental males’ in several species of Cirripedia. CD had observed minute males attached to the bodies of hermaphrodites, and differing greatly from them in size and structure (see Living Cirripedia (1851), pp. 231–2 and 281–93, Living Cirripedia (1854), pp. 23–30, and Newman 1993, pp. 377–81). In his letter to J. D. Hooker, 10 May 1848 (Correspondence vol. 4), CD remarked that the discovery was suggestive of the development of separate sexes, and thus of significance for his theory of species (see also Correspondence vol. 4, Appendix II, pp. 399–400). CD later suggested that complemental males might have developed in cirripedes to enable intercrossing between two hermaphrodites (see ‘On the males and complemental males of certain cirripedes, and on rudimentary structures’, Nature 8 (1873): 431–2; Collected papers 2: 177–82).
Naturae curiosi: inquirer into nature (Latin).

Bibliography

Claus, Carl Friedrich. 1874. Die Typenlehre und E. Haeckels sog. Gastraea-Theorie. Vienna: Manz.

Collected papers: The collected papers of Charles Darwin. Edited by Paul H. Barrett. 2 vols. Chicago and London: University of Chicago Press. 1977.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

Di Gregorio, Mario A. 2005. From here to eternity: Ernst Haeckel and scientific faith. Göttingen: Vandenhoeck & Ruprecht.

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.

Newman, William A. 1993. Darwin and cirripedology. History of Carcinology. Crustacean Issues 8: 349–434.

Nyhart, Lynn K. 1995. Biology takes form. Animal morphology and the German universities, 1800–1900. Chicago and London: University of Chicago Press.

Origin 5th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 5th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1869.

Summary

Sends a paper on reproductive modes of Leptodera ["Organisation und Fortpflanzen von Leptodera", Schr. Ges. Beförd. Naturw. Marburg (1869)].

Criticises Ernst Haeckel’s work as too unripe and enthusiastic.

Asks CD for some specimens of cirripedes in pupal stage for a work in progress.

Letter details

Letter no.
DCP-LETT-6575
From
Carl Friedrich Claus
To
Charles Robert Darwin
Sent from
Marburg
Source of text
DAR 161: 176
Physical description
6pp (German) †

Please cite as

Darwin Correspondence Project, “Letter no. 6575,” accessed on 22 November 2019, https://www.darwinproject.ac.uk/letter/DCP-LETT-6575.xml

Also published in The Correspondence of Charles Darwin, vol. 17

letter