From Ernst Haeckel1   11 January 1866

Jena (Saxe-Weimar)

11. Januar 1866

Hochverehrter theurer Herr!

Indem ich Ihnen zunächst ein recht glückliches neues Jahr wünsche und vor Allem, dass Ihre theure Gesundheit wieder ganz gekräftigt werden möge, zeige ich Ihnen den Empfang Ihrer beiden freundlichen Briefe (vom 6. Dec. and 5. Jan.)2 an, welche mir, wie alle Erinnerungen an Sie, stets von dem grössten Werthe sind und bleiben werden.3

Dass Sie meine letzten Arbeiten richtig empfangen haben, ist mir lieb.4 Mein Buchhändler (Engelmann in Leipzig) hatte ⁠⟨⁠sie⁠⟩⁠ schon im vorigen September an Willia⁠⟨⁠ms &⁠⟩⁠ Norgate abgesandt.5 Der Prot⁠⟨⁠ogenes⁠⟩⁠ primordialis (in dem Blatt: “⁠⟨⁠Sarcodekörper⁠⟩⁠ der Rhizopoden”) ist Ihnen ⁠⟨⁠hoffentlich⁠⟩⁠ von besonderem Interesse.6 Ich g⁠⟨⁠laube, dass⁠⟩⁠ solche Organismen (ganz hom⁠⟨⁠ogene⁠⟩⁠ Eiweiss-Klumpen oder Protoplasma ⁠⟨⁠    ⁠⟩⁠ im Anfange des organischen Lebens ⁠⟨⁠auf der⁠⟩⁠ Erde spontan entstanden sind, und ⁠⟨⁠dass⁠⟩⁠ sich aus ihnen durch “natural Sele⁠⟨⁠ction”⁠⟩⁠ zunächst verschiedenartige Zellen und daraus weiter durch Differenzirung die wenigen grossen Hauptklassen des Thier- und Pflanzen-Reichs gebildet haben, unter welche wir alle verschiedenen Organismen unterordnen können.7 Ich nehme solcher Hauptklassen (Typen, Branches, Embranchemens) ungefähr 10 oder 12 im Ganzen an und werde diese Annahme in meinem jetzt erscheinenden allgemeinen Buche dadurch zu beweisen suchen, dass ich einen ganzen Stammbaum (eine genealogische Tabelle) für jede derselben aufstelle.8 Der Druck dieses Buches schreitet jetzt rüstig vorwärts; indess wird es wohl immer noch einige Monate dauern, bis es erscheinen wird.9 Ein sehr wichtiges Capitel (die allgemeinen Principien ⁠⟨⁠u⁠⟩⁠nd Gesetze der embryonalen und der ihr ⁠⟨⁠par⁠⟩⁠allelen palaeontologischen Entwickelung) ⁠⟨⁠will⁠⟩⁠ ich noch ganz umarbeiten. Dieses und ⁠⟨⁠einige an⁠⟩⁠dere Capitel habe ich schon ⁠⟨⁠mehrere⁠⟩⁠ male umgearbeitet.10 Aber es ⁠⟨⁠ist se⁠⟩⁠hr schwierig, auf einem solchen ⁠⟨⁠neuen⁠⟩⁠ und uncultivirten Felde vorwärts ⁠⟨⁠zu k⁠⟩⁠ommen. Es ist wie ein dichter ⁠⟨⁠noch u⁠⟩⁠nbetretener Urwald, in welchem ⁠⟨⁠da⁠⟩⁠s Unkraut der Vorurtheile und die ⁠⟨⁠Dorn⁠⟩⁠en der Dogmen jeden Schritt aufhalten.

Wie viel ich mich bei dieser schweren Arbeit, die meine ganzen Kräfte in Anspruch nimmt, und mich dadurch zugleich am besten von meinem unglücklichen Schicksal ablenkt,11 mich mit Ihnen, theuer Herr, beschäftige, können Sie denken, und jedesmal, wenn mir eine neue Entdeckung auf dem intellectuellen Gebiete der philosophischen Naturbetrachtung welches Sie uns neu eröffnet haben, gelungen ist, möchte ich nach Down. Bromley. Kent. springen, um mich mit Ihnen darüber zu unterhalten. Ich bin gewiss, dass Sie sich darüber freuen würden und weiss im Voraus, dass Ihnen mein Buch viele Freude machen wird. Denn es hat noch Niemand die gesammte Morphologie auf den von Darwin entdeckten Principien umgearbeitet und mit Intensität und Consequenz die Descendenz Theorie auf alle Zweige derselben anzuwenden versucht. Es ist mir aber sehr schwer, Ihnen jetzt Einzelnes daraus mitzutheilen, da das Ganze eine fortlaufende Kette philosophischer Untersuchungen bildet.

Als lehrreichsten Beweis, zu welchen Thorheiten das Dogma von der Species-Constanz, und die teleologisch–dogmatische Behandlung der Morphologie führt, setze ich in meinem Buche den Ansichten von Darwin stets diejenigen von Agassiz gegenüber, welcher in der That das Maximum von Verkehrtheit und von unnatürlicher Behandlung der Natur geleistet hat.12 Da aber seine Ansichten immer noch viele Anhänger finden, sieht man, wie weit wir noch im Allgemeinen zurück sind.13

Meine öffentlichen Vorlesungen “über Darwins Theorie” sind, wie ich Ihnen wohl schon geschrieben habe, in diesem Winter die besuchtesten von allen Vorlesungen, die hier gehalten werden,14 und ich hoffe, dass ich dadurch viele fruchtbare Samenkörner ausstreue, welche zu kräftigen Stützen der Descendenz-Theorie heranwachsen werden.

Ich habe nun noch eine grosse Bitte, mein theurer Herr, die ich Ihnen schon lange vortragen wollte. Einer meiner lebhaftesten Wünsche ist, ein grösseres Portrait von Ihnen zu besitzen. Zwar habe ich über meinem Schreibtische die grössere Photographie (ohne vollen Bart) hängen, welche der zweiten Ausgabe Ihres Werkes vorgebunden war;15 und darunter habe ich die vortreffliche kleinere Photographie, welche Sie mir vor 2 Jahren zu schicken die Güte hatten.16 Allein die erstere ist gewiss schlecht, und die zweite zu klein, um mich zu befriedigen. Ich habe schon in allen Buchhandlungen in Berlin und anderen grösseren Orten gefragt, ob keine grössere Lithographie oder Photographie von Ihnen existirt, habe aber keine bekommen können. Vielleicht giebt es eine solche in England, und Sie würden mir eine ausserordentliche Freude machen, wollten Sie mir eine solche schicken. Ich bekomme sehr oft Besuch von vielen Schülern und Freunden, welche Ihr Bild sehen wollen, und ich bin dann immer betrübt, dass Ihre kleine Photographie (mit vollem Bart) nicht viermal oder sechsmal vergrössert werden kann. Um die kleine Photographie (in Visiten-Karten-Format) bin ich schon oft gebeten worden. Wenn Sie mir von dieser etwa 12 oder 1 Dutzend schicken könnten, so würde ich Ihnen dafür ebenso viele Photographien von deutschen Verehrern Darwins und Anhängern seiner Lehre zurück-schicken. Entschuldigen Sie meine, vielleicht kindische Bitte; aber sie liegt mir zu sehr am Herzen.17

Beifolgend lege ich eine Photographie von mir vom vorigen Oktober bei, damit Sie sehen, wie alt ich in 2 Jahren geworden bin.18

Indem ich Ihnen, theurer Herr, von ganzem Herzen die baldigste Kräftigung Ihrer Gesundheit wünsche, damit Sie uns und der Wissenschaft noch lange erhalten bleiben mögen, bleibe ich | von ganzem Herzen | Ihr treulichst ergebener | Ernst Haeckel.

1
For a translation of this letter, see Correspondence vol.14, Appendix I.
2
For the letter to Haeckel of 6 December [1865], see Correspondence vol. 13; the letter to Haeckel of 5 January 1866 has not been found.
3
CD and Haeckel had been corresponding since 1863 or earlier. Their earliest extant correspondence refers to earlier letters (see Correspondence vol. 11, letter to Ernst Haeckel, 30 December [1863] – 3 January [1864]).
4
In his letter of 11 November 1865, Haeckel listed three publications that were to be sent to CD (see Correspondence vol. 13). These were Haeckel 1865a, 1865b and 1865c, all papers on marine invertebrates of the class Coelenterata. A lightly annotated copy of Haeckel 1865a, inscribed by the author, is in the Darwin Pamphlet Collection–CUL. CD’s copy of Haeckel 1865b was listed in CD’s library catalogue (DAR 240), but was not listed in later catalogues. It has not been found in the Darwin Library–CUL or at Down. In his letter to Haeckel of 6 December [1865], CD acknowledged receipt of two other papers of Haeckel’s (Haeckel 1864 and 1865d). For a discussion of the role of Coelenterata in nineteenth-century debates over zoological classification and theories of descent, see Winsor 1976.
5
Wilhelm Engelmann was a publisher of scientific books (NDB; see also Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865). Williams & Norgate, booksellers and publishers of Covent Garden, London, and of Edinburgh, specialised in foreign and scientific literature (Modern English biography s.v. Williams, Edmund Sidney).
6
The reference is to Haeckel 1865a, a paper on rhizopods in which his newly discovered primitive species, Protogenes primordialis, was described and illustrated. Haeckel had previously drawn CD’s attention to this ‘organism’, emphasising its significance for his transmutation theory (see Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865 and nn. 11 and 12); a protoplasmic aggregate, without differentiation, organisation, or nucleus, it was able to surround and assimilate foreign bodies, and to reproduce by simple division (Haeckel 1865a, pp. 360–3). It is not recognised in modern taxonomic literature.
7
In his book Generelle Morphologie der Organismen, published later in 1866, Haeckel classified Protogenes primordialis in a new phylum, the Monera, comprising the most basic forms of life; he argued that the Rhizopoda might have evolved from a Protogenes species (Haeckel 1866, 2: XXII–XXIII). The taxonomic hierarchy proposed by Haeckel reflected CD’s transmutation theory, being based on descent from primitive life forms (Haeckel 1866, 2: XVII–XXII; see also n. 8, below). For discussions of Haeckel’s theories of protoplasm and the development of living organisms from inorganic matter, see Rehbock 1975 and Rupke 1976. On the Victorian debates over spontaneous generation, see Strick 2000.
8
The reference is to Haeckel 1866. Haeckel had previously written to CD about his work on this book (see Correspondence vol. 12, letter from Ernst Haeckel, 26 October 1864 and n. 8, and Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865 and n. 4). Inside the back cover of the second volume are eight genealogical trees, drawn by Haeckel, displaying the possible relationships among all living organisms. The first tree summarises all subsequent trees and has a central section representing the kingdom of ‘Protista’ (including unicellular organisms, fungi and sponges) flanked by the animal and plant kingdoms. Haeckel showed eleven main classes (subkingdoms): six within the plant and five within the animal kingdom (for a definition of Haeckel’s taxonomic categories, see Haeckel 1866, 2: 374–91). Haeckel’s evolutionary trees established a standard iconography for phylogeny (see, for example, S. J. Gould 1990, pp. 263–7). Their epistemological significance is considered in Bouquet 1995, pp. 47–51. CD earlier used a tree-like diagram to illustrate the divergence of offspring from parental types (Origin, facing p. 117; see also Winsor 1976, pp. 172–4). For Haeckel’s theoretical discussion of his phylogenetic categories, see Haeckel 1866, 2: XVII–XX, XXXI–XXXII, XLVIII–L, and 406–17.
9
Haeckel 1866 was published on or after 14 September 1866, the date appearing at the foot of the foreword.
10
Haeckel probably refers to chapter 21, ‘Begriff und Aufgabe der Phylogenie’ (Concept and function of phylogeny; Haeckel 1866, 2: 303–22), in which he developed arguments in support of the principle that ontogeny recapitulates phylogeny: ‘During its own rapid development … an individual repeats the most important changes in form evolved by its ancestors during their long and slow palaeontological development’ (Haeckel 1866, 2: 300; translated in S. J. Gould 1977, p. 76). For an extensive modern examination of Haeckel’s attempted theoretical connection of long-term evolutionary change with short-term growth and development, and a comparison with CD’s views, see S. J. Gould 1977.
11
After Haeckel’s wife, Anna Sethe, died on 16 February 1864, Haeckel wrote to CD: ‘a stroke of fate has destroyed all prospects of happiness in my life, and … I shall pursue the one goal in my life, namely to disseminate, to support and to perfect your theory of descent’ (English translation; see Correspondence vol. 12, letter from Ernst Haeckel, 9 [July 1864]; see also Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865 and n. 13).
12
There are approximately ten references to Louis Agassiz in Haeckel 1866; most make no direct comparison with CD. For more on Agassiz’s and Haeckel’s interpretations of taxonomic hierarchies, and their differing implications for evolutionary theory, see Bryant 1995, pp. 197–202 and 207 et seq.
13
For Agassiz’s views on the constancy of species, and his arguments against CD and Haeckel during the 1860’s, see Morris 1997. On support for Agassiz’s anti-Darwinian rhetoric in the early 1860s, see Lurie 1960, pp. 309–11.
14
According to Haeckel, over 150 people from a wide range of disciplines regularly attended his public lectures on CD’s theory in the academic year 1864 to 1865 (see Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865). Records of the university of Jena indicate that 120 people attended the lectures on Darwinian theory given by Haeckel in the main lecture theatre during the winter of 1865 to 1866 (Uschmann 1959, pp. 43–6, 196–8).
15
This photograph, procured from London by the German publisher, E. Schweizerbart’sche Verlagsbuchhandlung, was used as the frontispiece to the second German edition of Origin (see Correspondence vol. 10, letter from E. Schweizerbart’sche Verlagsbuchhandlung, 7 June 1862 and n. 5); it was taken by Maull & Polyblank, circa 1857. The photograph is reproduced as the frontispiece to Correspondence vol. 8.
16
Haeckel refers to the first photograph of CD with a beard, taken in 1864 by his son William Erasmus Darwin. The photograph is reproduced as the frontispiece to Correspondence vol. 12. See ibid., letter to Ernst Haeckel, 19 July [1864] and n. 7.
17
CD exchanged photographs with many of his correspondents during the 1860s (see Correspondence vols. 9–13, and Browne 1998, pp. 253–80).
18
The photograph has not been found. However, there is a portrait of Haeckel dated 1865 at the Ernst Haeckel Haus in Jena. An earlier portrait, presumably taken during 1863, was sent to CD in summer 1864, and included Haeckel’s late wife, Anna Sethe (see Correspondence vol. 12, letter from Ernst Haeckel, 10 August 1864; see also ibid., plate facing p. 280).

From Ernst Haeckel1   11 January 1866

Jena (Saxe-Weimar)

11 January 1866

Most esteemed Sir!

First of all wishing you a very happy New Year and above all that your health may be fully restored, I acknowledge the receipt of your two kind letters (of 6 Dec. and 5 Jan.).2 They are and will remain, as is the case with all mementos of you, always of the greatest value for me.3

I am pleased that you have received my latest works in good order.4 My publisher (Engelmann in Leipzig) had sent ⁠⟨⁠them⁠⟩⁠ to Williams & Norgate last September.5 ⁠⟨⁠I hope⁠⟩⁠ the ⁠⟨⁠Protogenes⁠⟩⁠ primordialis (in the paper: “⁠⟨⁠Sarcodekörper⁠⟩⁠ der Rhizopoden”) will be of particular interest to you.6 I ⁠⟨⁠believe that⁠⟩⁠ such organisms (quite ⁠⟨⁠homogeneous⁠⟩⁠ masses of gelatinous material or protoplasm ⁠⟨⁠    ⁠⟩⁠ emerged spontaneously in the beginning of organic life ⁠⟨⁠on⁠⟩⁠ earth, and ⁠⟨⁠that⁠⟩⁠ initially various kinds of cells developed from them by “natural selection”. By differentiation of these cells the few, large main classes of the animal and vegetable kingdoms evolved, under which we can subsume all the various organisms.7 I take it there are roughly 10 or 12 such main classes (types, branches, embranchments) in all, and I will attempt to prove this assumption in my general book, which is about to appear, by drawing up the entire family tree (a genealogical table) for each of them.8 The printing of this book is advancing vigorously; however, it will probably be several months yet before it appears.9 A very important chapter (general principles ⁠⟨⁠and⁠⟩⁠ laws of the embryonic and its ⁠⟨⁠parallel⁠⟩⁠ palaeontological development) I ⁠⟨⁠shall⁠⟩⁠ rework completely.10 This and ⁠⟨⁠a few other⁠⟩⁠ chapters have already been reworked ⁠⟨⁠several⁠⟩⁠ times. But ⁠⟨⁠it is very⁠⟩⁠ difficult to ⁠⟨⁠make⁠⟩⁠ progress in such a ⁠⟨⁠novel⁠⟩⁠ and uncultivated field. It is like a dense, ⁠⟨⁠still⁠⟩⁠-untrodden virgin forest where ⁠⟨⁠the⁠⟩⁠ weeds of prejudice and the ⁠⟨⁠thorns⁠⟩⁠ of dogma impede every step.

You can imagine how much I concern myself with you, dear Sir, in this difficult undertaking which absorbs all my energy and which thereby at the same time best distracts me from my unhappy fate.11 Every time I succeed in making a new discovery in the intellectual field of the philosophical study of nature that you have newly opened up for us, I want to hurry to Down, Bromley, Kent, in order to talk to you about it. I am certain that you would be pleased about it, and I know already that you will enjoy my book very much. For no one has yet recast the whole of morphology in accordance with the principles discovered by Darwin and attempted to apply the theory of descent to all of its branches with force and persistence. It is very difficult for me to convey any details to you now, however, because the whole consists of a continuous chain of philosophical investigations.

In my book I invariably juxtapose Darwin’s views with those of Agassiz, who indeed achieved the maximum of wrongheadedness and unnatural treatment of nature.12 This is the most didactic proof of the follies to which the dogma of the constancy of species and the teleological–dogmatic treatment of morphology can lead. However, that his views still find the support of many goes to show how far we still have to go.13

My public lectures “On Darwin’s theory” have, as I think I have already written to you, attracted the largest audiences of any lectures held here this winter,14 and I hope thereby to be spreading many a fertile seed, which will grow into powerful support for the theory of descent.

Lastly I have a big favour to ask of you, my dear Sir, which I have wanted to bring up for a long time. It is one of my keenest wishes to possess a larger portrait of you. Above my desk hangs the larger photograph (without full beard), the one at the front of the second edition of your work.15 Underneath it I have the excellent smaller photograph which you kindly sent me 2 years ago.16 However, the first for sure is poor and the second too small to satisfy. I have already made inquiries in all bookshops of Berlin and other larger towns whether there are any larger lithographs or photographs of you, but I have not found any. Perhaps such a one exists in England, and you would do me an extraordinary favour if you could send me one. I am often visited by many students and friends who would like to see your picture and it always saddens me that your small photograph (with the full beard) cannot be enlarged four or six times. I have often been begged for the little photograph (in calling card format). If you could send me about 12 or 1 dozen of these, I would in turn send you just as many photographs of German admirers of Darwin and supporters of his teachings. Please excuse my perhaps childish request—but it is of great importance to me.17

I enclose a photograph of myself from last October, so that you can see how much I have aged in 2 years.18

Wishing with all my heart, dear Sir, that your health may improve very soon so you will remain with us for a long time yet for our benefit and that of science, I remain | with all my heart | Yours truly devoted | Ernst Haeckel.

1
For a transcription of this letter in its original German, see pp. 6–8.
2
For the letter to Haeckel of 6 December [1865], see Correspondence vol. 13; the letter to Haeckel of 5 January 1866 has not been found.
3
CD and Haeckel had been corresponding since 1863 or earlier. Their earliest extant correspondence refers to earlier letters (see Correspondence vol. 11, letter to Ernst Haeckel, 30 December [1863] – 3 January [1864]).
4
In his letter of 11 November 1865, Haeckel listed three publications that were to be sent to CD (see Correspondence vol. 13). These were Haeckel 1865a, 1865b and 1865c, all papers on marine invertebrates of the class Coelenterata. A lightly annotated copy of Haeckel 1865a, inscribed by the author, is in the Darwin Pamphlet Collection–CUL. CD’s copy of Haeckel 1865b was listed in CD’s library catalogue (DAR 240), but was not listed in later catalogues. It has not been found in the Darwin Library–CUL or at Down. In his letter to Haeckel of 6 December [1865], CD acknowledged receipt of two other papers of Haeckel’s (Haeckel 1864 and 1865d). For a discussion of the role of Coelenterata in nineteenth-century debates over zoological classification and theories of descent, see Winsor 1976.
5
Wilhelm Engelmann was a publisher of scientific books (NDB; see also Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865). Williams & Norgate, booksellers and publishers of Covent Garden, London, and of Edinburgh, specialised in foreign and scientific literature (Modern English biography s.v. Williams, Edmund Sidney).
6
The reference is to Haeckel 1865a, a paper on rhizopods in which his newly discovered primitive species, Protogenes primordialis, was described and illustrated. Haeckel had previously drawn CD’s attention to this ‘organism’, emphasising its significance for his transmutation theory (see Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865 and nn. 11 and 12); a protoplasmic aggregate, without differentiation, organisation, or nucleus, it was able to surround and assimilate foreign bodies, and to reproduce by simple division (Haeckel 1865a, pp. 360–3). It is not recognised in modern taxonomic literature.
7
In his book Generelle Morphologie der Organismen, published later in 1866, Haeckel classified Protogenes primordialis in a new phylum, the Monera, comprising the most basic forms of life; he argued that the Rhizopoda might have evolved from a Protogenes species (Haeckel 1866, 2: XXII–XXIII). The taxonomic hierarchy proposed by Haeckel reflected CD’s transmutation theory, being based on descent from primitive life forms (Haeckel 1866, 2: XVII–XXII; see also n. 8, below). For discussions of Haeckel’s theories of protoplasm and the development of living organisms from inorganic matter, see Rehbock 1975 and Rupke 1976. On the Victorian debates over spontaneous generation, see Strick 2000.
8
The reference is to Haeckel 1866. Haeckel had previously written to CD about his work on this book (see Correspondence vol. 12, letter from Ernst Haeckel, 26 October 1864 and n. 8, and Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865 and n. 4). Inside the back cover of the second volume are eight genealogical trees, drawn by Haeckel, displaying the possible relationships among all living organisms. The first tree summarises all subsequent trees and has a central section representing the kingdom of ‘Protista’ (including unicellular organisms, fungi and sponges) flanked by the animal and plant kingdoms. Haeckel showed eleven main classes (subkingdoms): six within the plant and five within the animal kingdom (for a definition of Haeckel’s taxonomic categories, see Haeckel 1866, 2: 374–91). Haeckel’s evolutionary trees established a standard iconography for phylogeny (see, for example, S. J. Gould 1990, pp. 263–7). Their epistemological significance is considered in Bouquet 1995, pp. 47–51. CD earlier used a tree-like diagram to illustrate the divergence of offspring from parental types (Origin, facing p. 117; see also Winsor 1976, pp. 172–4). For Haeckel’s theoretical discussion of his phylogenetic categories, see Haeckel 1866, 2: XVII–XX, XXXI–XXXII, XLVIII–L, and 406–17.
9
Haeckel 1866 was published on or after 14 September 1866, the date appearing at the foot of the foreword.
10
Haeckel probably refers to chapter 21, ‘Begriff und Aufgabe der Phylogenie’ (Concept and function of phylogeny; Haeckel 1866, 2: 303–22), in which he developed arguments in support of the principle that ontogeny recapitulates phylogeny: ‘During its own rapid development … an individual repeats the most important changes in form evolved by its ancestors during their long and slow palaeontological development’ (Haeckel 1866, 2: 300; translated in S. J. Gould 1977, p. 76). For an extensive modern examination of Haeckel’s attempted theoretical connection of long-term evolutionary change with short-term growth and development, and a comparison with CD’s views, see S. J. Gould 1977.
11
After Haeckel’s wife, Anna Sethe, died on 16 February 1864, Haeckel wrote to CD: ‘a stroke of fate has destroyed all prospects of happiness in my life, and … I shall pursue the one goal in my life, namely to disseminate, to support and to perfect your theory of descent’ (English translation; see Correspondence vol. 12, letter from Ernst Haeckel, 9 [July 1864]; see also Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865 and n. 13).
12
There are approximately ten references to Louis Agassiz in Haeckel 1866; most make no direct comparison with CD. For more on Agassiz’s and Haeckel’s interpretations of taxonomic hierarchies, and their differing implications for evolutionary theory, see Bryant 1995, pp. 197–202 and 207 et seq.
13
For Agassiz’s views on the constancy of species, and his arguments against CD and Haeckel during the 1860’s, see Morris 1997. On support for Agassiz’s anti-Darwinian rhetoric in the early 1860s, see Lurie 1960, pp. 309–11.
14
According to Haeckel, over 150 people from a wide range of disciplines regularly attended his public lectures on CD’s theory in the academic year 1864 to 1865 (see Correspondence vol. 13, letter from Ernst Haeckel, 11 November 1865). Records of the university of Jena indicate that 120 people attended the lectures on Darwinian theory given by Haeckel in the main lecture theatre during the winter of 1865 to 1866 (Uschmann 1959, pp. 43–6, 196–8).
15
This photograph, procured from London by the German publisher, E. Schweizerbart’sche Verlagsbuchhandlung, was used as the frontispiece to the second German edition of Origin (see Correspondence vol. 10, letter from E. Schweizerbart’sche Verlagsbuchhandlung, 7 June 1862 and n. 5); it was taken by Maull & Polyblank, circa 1857. The photograph is reproduced as the frontispiece to Correspondence vol. 8.
16
Haeckel refers to the first photograph of CD with a beard, taken in 1864 by his son William Erasmus Darwin. The photograph is reproduced as the frontispiece to Correspondence vol. 12. See ibid., letter to Ernst Haeckel, 19 July [1864] and n. 7.
17
CD exchanged photographs with many of his correspondents during the 1860s (see Correspondence vols. 9–13, and Browne 1998, pp. 253–80).
18
The photograph has not been found. However, there is a portrait of Haeckel dated 1865 at the Ernst Haeckel Haus in Jena. An earlier portrait, presumably taken during 1863, was sent to CD in summer 1864, and included Haeckel’s late wife, Anna Sethe (see Correspondence vol. 12, letter from Ernst Haeckel, 10 August 1864; see also ibid., plate facing p. 280).

Please cite as “DCP-LETT-4973,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-4973