skip to content

Darwin Correspondence Project

From C. F. Claus1   6 February 1869

Marburg

d 6/II 1869

Hochgeehrter Herr!

Sie haben mir durch Ihre gütigen Zeilen eine ebenso grosse Freude als Ehre erwiesen, und weiss ich in der That kaum, wie ich mich für das in Aussicht gestellte Untersuchungsmaterial dankbar beweisen kann.2 Ich hoffe durch eine möglichst sorgfältige und gewissenhafte Prüfung jener so interessanten und wichtigen Objecte mich Ihrer grossen Güte und Ihres Vertrauens einigermassen würdig zu zeigen. Ich werde die bezeichneten Gegenstände mit dem grössten Danke acceptiren. Da ich bislang nur die Larven und Puppen von Lepadiden untersuchen könnte, so würde ich Ihnen auch besonders verpflichtet sein, wenn Sie mir vielleicht die Gelegenheit verschaffen könnten, die Puppen von Balanus zu examiniren; ich sollte denken, die Post würde ein solch’ kleines Kästchen, welches ich Sie bitten würde, an das Königliche zoologische Institut zu adressiren, leicht annehmen und beförderen—

In einer kleinen Notiz, die ich neben mehreren Arbeiten mir erlaubt habe an Sie in Kreuzband abzusenden, habe ich schon 1862 den Versuch gemacht, den Cirripedienleib auf den der Copepoden morphologisch zurückzuführen.3 Meine neueren Studien der Larven, Puppen und jungen in Puppen eingeschlossenen Cirripedien, haben hoffe ich meine damalige Zurückführung ziemlich sicher gestellt.4 Die Organe in den Hörnern der Larve sind jedenfalls Sinnesorgane und mit Fäden ausgestattet den Sinnesfäden (Leydigschen Organen) niederer Crustaceen vergleichbar, sie sind offenbar dasselbe, was Sie als Gehörorgane in der Puppe dargelegt haben, deren Stirnecken den Stirnhörnern der Larve entsprechen.5 Die feinere Bestimmung dieser Organe ist leider nur an frischen Puppen möglich, ich konnte leider nur Spiritusexemplare untersuchen.

Bezüglich der Schrift von Wagner6 dürfte wohl auch hervorzuheben sein, dass die allmähligen tellurischen und klimatischen Veränderungen als Ursache der Veränderungen in den Lebensbedingungen und Wechselbeziehungen der Organismen viel zu gering geschätzt worden sind. Die Migration mag besonders in Betracht kommen zur Erklärung der räumlich neben einander enstehenden geographischen Varietäten, die letztern dagegen zur Erklärung der zeitlich aufeinanderfolgenden Abänderungen. Im letzteren Falle ist die Migration secundär und Folge nicht wie Wagner glaubt primäre Ursache. Auch haben Sie, sollte ich denken, durch die Darlegung der 2 erdachten Beispiele, insbesondere der langbeinigen schnellern und kurzer beinigen Wolfrasse sehr wahrscheinlich gemacht, dass auch ohne so strenge Isolierung, wie sie Hochgebirge, Ströme und Meere bedingen, Varietäten räumlich neben einander hervorgehn können. Das hat Wagner nicht widerlegt, sondern nur seine Behauptung einfach entgegengehalten—.

Es gereicht mir zur besondern Ehre, Ihnen, hochverehrter Herr, meine Photographie beilegen zu dürfen.7 Ich würde mich glücklich schätzen, die Ihrige mit Ihrer eigenhändigen Namensunterschrift zu besitzen und in meinem zoologischen Album an die Spitze der Naturforscher stellen zu können, die durch ihre Arbeiten in die Entwicklung der Wissenschaft gewaltig eingreifend, umgestaltend und aufbauend gewirkt haben.

Dass R Leuckart 8 einen Ruf nach Leipzig erhalten und angenommen hat, wird Ihnen wohl noch nicht bekannt sein.

Mit ausgezeichter Hochachtung und Verehrung unterzeichne ich als Ihr ergebenster | C Claus

P.S. In der kleinen Schrift “über die Copepodenfauna Nizza’s im Sinne Darwin’s habe ich die Bemerkungen Fr. Müller’s über die zwei Männchen von Tanaïs d. (Riecher und Packer) in ihrem Werthe in Zweifel gezogen.9 Ich darf mir wohl erlauben, Ihnen uber die Naupliuslarven der Garneelen meine Zweifel nicht vorzuenthalten. Fr. Müller hat nicht bewiesen, weder dass die sog. Naupliuslarven aus den Eiern von Peneus hervorgingen noch dass die Zoëastadien nach Abstreifung der Haut aus den Naupliuslarven sich entwickelten. Das neben einander Vorkommen der Naupliusformen und Zoestadien berechtigt nicht zu dem Schlusse, dass diese die jüngeren Stadien der letzteren sein, was noch zu beweisen ist.10

Es mag vollkommen wahr sein, aber die Sicherheit fehlt. Meine Zweifel aber sind nunmehr geradezu angeregt durch die Grösse der Eier von einer nicht näher bestimmten Peneus art. Ein so grosses Ei lässt auf die vollkommenere Ausbildung des Embryos und der ausschlüpfenden Larve schliessen—

In etwa vier Wochen fangen die Ferien an und ich habe dann sechs Wochen freie Zeit, um mich ausschlieslich der Cirripedienarbeit widmen zu können. Sollten Sie indessen, hochverehrter Herr, bis dahin nicht wohl Zeit haben, mir das Material zuzusenden, so würde ich auch bis in den Sommer warten können, ich möchte um keinen Preis Ihre kostbare Zeit im unrechten Augenblick in Anspruch nehmen. Ihr | C Claus

Footnotes

For a translation of this letter, see Correspondence vol. 17, Appendix I.
CD had offered to send some specimens of barnacles. See letter to C. F. Claus, 28 January 1869.
Claus refers to his paper on the morphological relations between copepods and other crustacean groups, including cirripedes (Claus 1862; for the section on cirripedes, see pp. 161–2). CD’s copy of the paper has not been found.
With his letter of 24 January 1869, Claus had enclosed an offprint of his article on the cypris-like larvae of cirripedes and their transformation into sedentary adults (Claus 1868b).
Claus refers to CD’s description of acoustic organs in the final pre-adult stage (cypris) of Lepas australis (Living Cirripedia (1851), p. 15). For more on CD’s view of the homologies of the naupliar, cyprid, and adult horns and antennae, see Newman 1993, pp. 372–4. In modern terminology, the ‘Leydig organ’ is the organ found near the oesophagus of sharks and other members of the subclass Elasmobranchii, and is associated with the immune system. Claus probably refers to an organ described by Franz von Leydig in a monograph on Daphnia as an analogue of the green gland in decapods (Leydig 1860, pp. 25–6).
Claus refers to Moritz Wagner and Wagner 1868a or 1868b. See letter from C. F. Claus, 24 January 1869 and n. 4.
The photograph has not been found.
Rudolf Leuckart.
Claus refers to his study, Die Copepoden-Fauna von Nizza. Ein Beitrag zur Charakteristik der Formen und deren Abänderungen ‘im Sinne Darwin’s’ (The copepod fauna of Nice. A contribution on the diagnosis of its form and its modification ‘in the Darwinian sense’; Claus 1866). In Für Darwin (F. Müller 1864a, pp. 13–16; Dallas trans. 1869, pp. 20–4), Fritz Müller had described two forms of male in Tanais dubius (now Leptochelia dubia). Claus questioned whether one might be the sexually mature form of the other, as was the case with the amphipod Phronima (see Claus 1866, pp. 1 and 2). In Origin 4th ed., p. 50, CD had noted Müller’s discovery of the two forms of male; the passage remained unchanged in subsequent editions. In Descent 1: 328–9, CD cited Müller at greater length on Tanais.
Müller had suggested that Penaeus emerged from the egg in its nauplius state in a paper, ‘Die Verwandlung der Garneelen’ (F. Müller 1863, p. 8), that appeared in English as ‘On the metamorphoses of the prawns’ (F. Müller 1864b, p. 104). Müller’s observation was only confirmed much later (Kishinouye 1900), but Claus evidently accepted Müller’s account when he made his own observations on development in the genus (see Claus 1876, pp. 10–13).

Translation

From C. F. Claus1   6 February 1869

Marburg

6/II 1869

Most esteemed Sir!

With your kind lines you have given me as much pleasure as honour, and indeed I scarcely know how I can show my gratitude for the research material you promised me.2 I hope, through the most careful and conscientious examination possible of these very interesting and important subjects, to prove myself in some way worthy of your great kindness and of your trust. I will accept the specimens referred to with my deepest gratitude. As I have hitherto been able to analyse only the larvae and pupae of Lepadidae, I would also be particularly obliged to you if you could possibly provide me with an opportunity of examining the pupae of Balanus; I should think that the postal service would easily accept and deliver such a little box which I would ask you to address to the Königliche Zoologische Institut—

In a small note that I have permitted myself to send to you under wrapper, along with a number of other works, I have already in 1862 made an attempt to trace back the morphology of the cirripede body to that of copepods.3 My more recent studies of the larvae, pupae and young cirripedes that are still enclosed in their pupae have, so I hope, largely borne out this earlier analysis.4 The organs in the horns of the larva are in any case sensory organs and equipped with hairs comparable to the sensory hairs (Leydig organs) of lower crustaceans; they are obviously identical with what you presented as the acoustic organs of the pupa, whose sternal edges correspond to the sternal horns of the larva.5 Unfortunately, a finer determination of these organs can only be carried out on fresh pupae, and regrettably I was only able to examine spirit specimens.

Regarding Wagner’s pamphlet,6 surely it should also be emphasised that gradual tellurian and climatic changes have been greatly underestimated as a cause of change in the conditions of existence and the interactions among organisms. Migration may be of importance especially in accounting for geographical varieties that develop side by side, the latter, on the other hand, in accounting for chronologically successive variations. In the latter case migration is secondary and an effect, not, as Wagner believes, a primary cause. Furthermore you have, I should have thought, with your account of the 2 imaginary examples, particularly that of the long-legged, faster, and shorter-legged wolves, made it very probable that even without such strict isolation as is produced by mountains, streams and oceans, variations can develop side by side in the same area. This Wagner has not refuted, but merely contrasted it with his own assertion—.

I feel it a special honour, esteemed Sir, to be able to enclose my photograph.7 I would consider myself fortunate to own one of you, signed by your own hand, and to be able to insert it in my zoological album at the summit of naturalists who through their work have had a powerfully radical, transforming and constructive impact on the development of science.

I expect you have not yet heard that R Leuckart8 has been offered and accepted a position at the University of Leipzig.

With the greatest respect and veneration I remain your most devoted | C. Claus

P.S. In a pamphlet “A Darwinian account of the copepod fauna of Nice” I questioned the value of Fr. Müller’s remarks on the two male forms of Tanais d. (smellers and graspers).9 Surely I may be allowed not to withhold from you my doubts about the nauplius larvae of the prawn. Fr. Müller has neither proven that the so-called nauplius larvae develop from the eggs of Peneus nor that the zoea stage develops from nauplius larvae after the skin has been shed. The simultaneous occurrence of the forms of nauplius and the stages of zoea does not warrant the conclusion that the former are the earlier stages of the latter, which still remains to be shown.10

It may be perfectly true, but the certainty is missing. And my doubts are now aroused by the size of the eggs of a species of Peneus as yet not precisely identified. From an egg of this size one may infer a fuller development of both embryo and hatching larva—

In about four weeks the holidays will begin and I shall have six weeks to apply myself exclusively to the study of cirripedes. In the meantime, should you, esteemed Sir, not have the time to send me the material until then, I can well wait until summer, for I should not at any price want to take up your time at the wrong moment. Yours | C. Claus.

Footnotes

For a transcription of this letter in its original German, see pp. 67–9.
CD had offered to send some specimens of barnacles. See letter to C. F. Claus, 28 January 1869.
Claus refers to his paper on the morphological relations between copepods and other crustacean groups, including cirripedes (Claus 1862; for the section on cirripedes, see pp. 161–2). CD’s copy of the paper has not been found.
With his letter of 24 January 1869, Claus had enclosed an offprint of his article on the cypris-like larvae of cirripedes and their transformation into sedentary adults (Claus 1868b).
Claus refers to CD’s description of acoustic organs in the final pre-adult stage (cypris) of Lepas australis (Living Cirripedia (1851), p. 15). For more on CD’s view of the homologies of the naupliar, cyprid, and adult horns and antennae, see Newman 1993, pp. 372–4. In modern terminology, the ‘Leydig organ’ is the organ found near the oesophagus of sharks and other members of the subclass Elasmobranchii, and is associated with the immune system. Claus probably refers to an organ described by Franz von Leydig in a monograph on Daphnia as an analogue of the green gland in decapods (Leydig 1860, pp. 25–6).
Claus refers to Moritz Wagner and Wagner 1868a or 1868b. See letter from C. F. Claus, 24 January 1869 and n. 4.
The photograph has not been found.
Rudolf Leuckart.
Claus refers to his study, Die Copepoden-Fauna von Nizza. Ein Beitrag zur Charakteristik der Formen und deren Abänderungen ‘im Sinne Darwin’s’ (The copepod fauna of Nice. A contribution on the diagnosis of its form and its modification ‘in the Darwinian sense’; Claus 1866). In Für Darwin (F. Müller 1864a, pp. 13–16; Dallas trans. 1869, pp. 20–4), Fritz Müller had described two forms of male in Tanais dubius (now Leptochelia dubia). Claus questioned whether one might be the sexually mature form of the other, as was the case with the amphipod Phronima (see Claus 1866, pp. 1 and 2). In Origin 4th ed., p. 50, CD had noted Müller’s discovery of the two forms of male; the passage remained unchanged in subsequent editions. In Descent 1: 328–9, CD cited Müller at greater length on Tanais.
Müller had suggested that Penaeus emerged from the egg in its nauplius state in a paper, ‘Die Verwandlung der Garneelen’ (F. Müller 1863, p. 8), that appeared in English as ‘On the metamorphoses of the prawns’ (F. Müller 1864b, p. 104). Müller’s observation was only confirmed much later (Kishinouye 1900), but Claus evidently accepted Müller’s account when he made his own observations on development in the genus (see Claus 1876, pp. 10–13).

Summary

Pleased by CD’s good opinion and offer to provide material. Discusses work he would do on cirripedes.

Moritz Wagner’s views on migration of species;

his doubts about Fritz Müller’s views on developmental stages of Crustacea.

Letter details

Letter no.
DCP-LETT-6605
From
Carl Friedrich Claus
To
Charles Robert Darwin
Sent from
Marburg
Source of text
DAR 161: 177
Physical description
6pp (German) †

Please cite as

Darwin Correspondence Project, “Letter no. 6605,” accessed on 19 June 2019, http://www.darwinproject.ac.uk/DCP-LETT-6605

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

letter