Haeckel, Ernst Heinrich Philipp August

Haeckel, Ernst Heinrich Philipp August

(b. Potsdam, Germany, 16 February 1834; d. Jena, Germany, 9 August 1919)

zoology.

Haeckel’s father, Carl Haeckel, was chief administrative advisor for religious and educational affairs in Merseburg. His mother, Charlotte Sethe, was the daughter of a privy councillor in Berlin.

Haeckel graduated from the Domgymnasium at Merseburg in 1852. After studying medicine at Berlin, Würzburg, and Vienna, he earned his medical degree at Berlin in 1857 and passed the state medical examination there in 1858. In 1861 he qualified as a lecturer in comparative anatomy at the Faculty of Medicine of the University of Jena. Appointed associate professor of zoology in the Faculty of Philosophy in 1862, he was promoted to full professor and director of the Zoological Institute in 1865. He retired in 1909.

Haeckel married his cousin Anna Sethe in 1862. She died in 1864 and in 1867 he married Agnes Huschke, the daughter of the anatomist Emil Huschke. Powerfully built, Haeckel enjoyed gymnastics and swimming, although for a time he suffered from rheumatoid arthritis. He worked quickly and intensively over long periods, offsetting this pace with long hikes and extended trips. Haeckel was also a member of more than ninety learned societies and scientific associations, including the Leopoldine Academy (1863), the Bavarian Academy of Sciences at Munich (corresponding member, 1870; foreign member, 1891), the Imperial Academy of Sciences at Vienna (corresponding member, 1872), the Royal Academy of Sciences at Turin (corresponding member, 1881; foreign member, 1898), the Royal Swedish Academy of Sciences at Stockholm (associate member, 1882), the Royal Lombard Institute of Sciences and Letters at Milan (corresponding member, 1884), the American Philosophical Society (1885), the Royal Society of Edinburgh (1888), and the Royal Academy of Sciences of the Institute at Bologna (1909). He was the recipient of many scientific honors.

During his school years Haeckel was an enthusiastic botanist and began an extensive herbarium that is still of scientific value.¹ After reading Matthias Schleiden’s popular book Die Pflanze und ihr Leben (1848) and accounts of various expeditions, including those of Darwin, Humboldt, and Robert Schomburgk, Haeckel wanted to study botany under Schleiden at Jena and then to undertake scientific expeditions of his own. From a very early age drawing and painting were among his favorite pursuits. His aptitude for rapidly and accurately classifying plants, his love of collecting, and his pleasure in artistic activity marked all of his later work.

In 1852 Haeckel gave up his own plans to follow his parents’ wish that he study medicine. After a period of resistance he realized that medical school offered him the most solid foundation for further scientific study. But this reconciliation to medicine did not extend to clinical medicine, since Haeckel never seriously intended to become a physician. While studying under Albert von Kölliker and Franz Leydig at Würzburg he became interested in comparative anatomy and embryology, as well as in microscopical investigations. At the same time, Haeckel was also influenced by the “mechanistic conception of the life processes” put forward by Rudolf Virchow, who at that time (1853) was in the midst of writing his Cellularpathologie.²

At Berlin in 1854–1855, however, Haeckel found in Johannes Müller “an authority recognized by all,” and Müller became his “scientific ideal.” Under his guidance Haeckel deepened his knowledge of comparative anatomy and was introduced to marine zoology, a field which, through Müller’s studies of the lower marine animals on Helgoland and in the Mediterranean, was advancing the development of scientific zoology.

At Würzburg, moreover, Haeckel was confronted for the first time with materialistic conceptions of life. He considered such views—which he encountered in Virchow’s lectures, in the writings of Carl Vogt, and in discussions with young scientists and physicians—to be the “opposite extreme” of the “caricature of the Christian religion” represented by dogmatic Catholicism. From the letters Haeckel wrote during these years it is evident that he was already leaning toward a compromise between Christianity and mechanistic materialism, a compromise he believed he had found by 1866 in his “monism.”

Haeckel’s first zoological work was his doctoral dissertation, Über die Gewebe des Flusskrebses (1857). He had intended, after finishing his medical studies in 1858, to complete his training in comparative anatomy and zoology at Berlin under Müller, but these plans were frustrated by Müiler’s death. At this time the anatomist Karl Gegenbaur offered Haeckel the attractive prospect of a future zoology professorship at Jena and encouraged him to undertake a zoological expedition in the Mediterranean. In the course of this trip (1859–1860) Haeckel discovered, following up Müller’s last work on radiolarians at Messina, 144 new radiolarián species, thereby establishing the basis for the monograph Die Radiolarien (1862). This work contains Haeckel’s first avowal of Darwinism, to which he was immediately converted upon reading the German translation of Darwin’s On the Origin of Species.

Darwin’s book provided a foundation and a direction for Haeckel’s future work. His technical writings on zoology, some of them long monographs, treated the morphology, systematics, and embryology of the radiolarians, medusae, siphonophores, sponges, and echinoderms. The research for these works was carried out with the methods of the prephylogenetic period, and they clearly show Müller’s influence. The new element consisted at first in the interpretation of the results in the light of Darwin’s theory: the systems of the recent organisms were considered to be the reflected images of their phylogenetic development. But Haeckel was not satisfied with interpreting Darwin’s theory of evolution and furnishing additional evidence for it. He thought his task lay in the further development of Darwinism. In his view this development ought to lead not only to a reform of the whole of biology; it should also provide the foundation for a science-based world view. Toward this goal he published his Generelle Morphologie der Organismen in 1866.

At the time Haeckel was writing this treatise, some eminent scientists had already publicly supported Darwin, while others were skeptical of his theory or rejected it completely. In addition the ideological consequences inherent in Darwinism had touched off vehement disputes. While Darwin himself did not take part in these debates, Haeckel deliberately refused to restrict himself to the field of biology.

The goal of the reformed morphology that Haeckel sought was not only to describe the forms of organisms but also to account for them in terms of the theory of evolution. This morphology was consequently divided into anatomy, or the science of developed forms (tectology and promorphology), and morphology, or the science of emerging forms (ontogeny and phylogeny). For Haeckel the correct method of research was “philosophical empiricism,” the interaction of induction and deduction. The mechanical-causal approach was to take the place of any dogmatic or vitalistic-teleological way of viewing nature. Following the linguist August Schleicher,³ Haeckel termed the philosophical system that corresponded to this approach “monism,” the unity of mind and matter, in contrast with dualism, the separation of mind and matter.

Accordingly, in this system there are no absolute differences between organic and inorganic substances, only relative ones. Haeckel contended that the material basis of the true life phenomena, nourishment and reproduction, lay in the very intricate chemical composition of the carbon compounds and in the resultant unique physical properties (above all the capacity for imbibition). In contrast with Darwin, Haeckel asserted that the theory of evolution could be applied even to the emergence of the first primal organisms, which were formed spontaneously through abiogenesis. First complex molecules were formed, followed by a formless plasma clump, or Moner. From one or from several such Moner one could deduce the genealogical tree of the entire organic kingdom. In his classificatory scheme Haeckel inserted an intermediate kingdom of prostista between animals and plants. Each organic kingdom consisted of several Stämmen, or phyla. The Stamm, or phyhlum, was “the totality of all the organisms existing at present, or that are extinct, that are descended from one and the same common progenitor.”

The “natural system” of the organisms is, according to Haeckel, “their natural family tree, the table of their genealogical relationships.” He first published such genealogical tables or “family trees” in the Generelle Morphologie for organisms (plants, prostista, animals), plants, coelenterates, echinoderms, articulates (infusorians, worms, arthropods), mollusks, vertebrates, and mammals (including man).

Haeckel continually strove to produce a comprehensive theory of the process of evolution by demonstrating regularities, the majority of which were of a speculative nature. He set forth a series of laws of heredity that, unlike those of Mendel, were not based on experiment. Haeckel distinguished between conservative heredity (the inheritance of heritable characters) and progressive heredity (the inheritance of acquired characters). The interaction of progressive and conservative heredity, he held, makes possible the transmutation of species.

In Haeckel’s view, the cell nucleus governs the inheritance of heritable characters and the plasma regulates the organism’s adaptation to the environment. He repeatedly asserted that without the Darwinian theory “all the great and universal phenomena of organic nature” are incomprehensible and inexplicable. This insistence on the fundamental importance of Darwin’s ideas is most apparent in his “ecology” and “chorology” of organisms. Haeckel defined ecology as “the comprehensive science of the relationships of the organism to the environment,” encompassing all the conditions of existence of organic and of inorganic nature. Chorology he defined as “the entire science of the spatial distribution of organisms, that is, of their geographical and topographical extension over the earth’s surface.” Both concepts have won acceptance.

Haeckel considered the causal nexus of biontic and phyletic development to be an important law: “Ontogeny is the short and rapid recapitulation of phylogeny determined by the physiological functions of heredity (propagation) and adaptation (nourishment).” For this relationship, which had been formulated before him, he later (1872) coined the expression “fundamental biogenetic law.” According to Haeckel this law was especially important because the embryological and systematic data available were much more complete than the paleontological. He divided phylogeny into three stages: epacme (blossoming), acme (peak flowering), and paracme (withering).

Drawing on the earlier writings of T. H. Huxley, Carl Vogt, Rolle, Filippo de Filippi, and Charles Lyell, Haeckel undertook a thorough study of the origin of man, setting the Tertiary as the time when man developed from the apes. He thought that the most important advance in that process was the “differentiation of the larynx, which resulted in the development of language and, consequently, of clearer communication and of historical tradition.” In Haeckel’s outline of a natural system, man is included among the tailless Catarrhinae; the term Pithecanthropus, which he coined, first appeared in this context.

For Haeckel anthropology was a part of zoology, since “man is separated from the other animals only by quantitative, not qualitative, differences,” and since the methods of comparative anatomy can be applied to man.

In the concluding section of Generelle Morphologie Haeckel discussed “the unity of nature and the unity of science (system of monism)” as well as “God in nature (pantheism and monotheism).” Here he showed the significance of embryology for human knowledge generally, which in his view finds its most comprehensive expression in a “cosmology or nature philosophy.” This philosophy was for him “identical with natural theology.” Monism is conceived of here as the purest monotheism, in which God corresponds to the general causal law (“the unity of God in nature”).

Generelle Morphologie contained all the essential aspects of Haeckel’s later work. After 1866 he changed neither his methods nor his goal in any significant way. His zoological works included descriptions of approximately 4,000 new species of lower marine animals—mainly radiolarians, medusae, and sponges. For these groups of animals he established phylogenetically interpreted “natural systems.”

Haeckel’s concept of matter provides an especially clear illustration of the discrepancy between the scientific basis of his work and the pretentious theoretical structure he erected upon it. Even in his last publication, Kristallseelen (1917), he persisted in the defense of his thesis on the “ensoulledness” of inorganic nature.

In his monograph Die Kalkschwämme (1872) Haeckel distinguished the ascon, sycon, and leucon types of sponges, all of which, he held, were descended from a common primal form (olynthus). He derived this primal form from the gastrula stage by employing the “fundamental biogenetic law.” In their ontogeny the sycon and leucon forms passed through the olynthus form.⁴ He saw in the gastrula an image of the hypothetical primal form of all metazoans. This conception was the basis of his “gastraea theory” (1874–1877) of the homology of the two primary cotyledons. Although his demonstration of this theory rested on false assumptions, Haeckel had nevertheless taken up a problem that has since been the subject of an extensive literature.

Stimulated by Darwin’s pangenesis hypothesis, Haeckel put forth his own hypothesis of the mechanism of heredity in 1876. According to it, heredity is “the transmission of the plastidial motion, [that is] the propagation of the individual molecular motion of the plastidial from the mother plastid to the daughter plastid.” Haeckel thought that new adaptations could occur through alterations of the original plastidial motions resulting from the varying conditions of existence of the daughter cells. He persevered in his belief in “the inheritance of acquired characters” in Lamarck’s sense and thereby became involved in a controversy with August Weismann, who about 1880 countered Lamarckism with his own “Neo-Darwinism.” Although after 1900 Haeckel learned of Mendel’s findings, he did not grasp the importance of experimental genetics.

Haeckel concluded his series of long zoological monographs in 1887–1889 with a treatment of the radiolarians, siphonophores, and deep-sea keratosa gathered on the Challenger expedition. Next, besides studies such as those on the plankton (1890), he wrote Systematische Phylogenie (1894–1896), subtitled Entwurf eines natürlichen Systems der Organismen auf Grund ihrer Stammesgeschichte. In this work Hacekel sought to present the advances made in phylogeny since the appearance of his Generelle Morphologie. Here again he contended that the foundation of the phylogenetic hypotheses lay in the direct empirical evidence of paleontology as well as in the indirect evidence of ontogeny and morphology.

In the chapter on the phylogeny of man Haeckel emphasized the incompleteness of the fossil record of the vertebrates. In his view, paleontological data was important primarily because it illustrated the sequence of descent among the individual vertebrate groups and their successive occurrences. At the same time he held that the unity of the vertebrates (including man) was already sufficiently demonstrated by comparative anatomy and ontogeny. “Laymen and one-sidedly trained specialists,” he stated, place too great a value on the evidence of “fossil men” and on the “transition forms from ape to man.”

It is therefore understandable that Haeckel did not discuss the prehistoric Homo neanderthalensis at all until 1900, whereas other scientists, including Huxley (1863) and Rolle (1866), early appreciated the importance of this discovery from the point of view of the theory of evolution. Only in his genealogical sketches of 1907 and 1908 did Haeckel upgrade Neanderthal man (Homo primigenius) to the intermediate stage (Protanthropus) “between Pithecanthropus and Homo australis, the lowest race of recent man” (1908).

Neither Generelle Morphologie nor Systematische Phylogenie had the success in scientific circles for which Haeckel had hoped. The evolutionary views he expressed in popular lectures, essays, and books had a far greater influence. In these writings, such as Natürliche Schöpfungs-Geschichte (1868) and Anthropogenie (1874), “monism” is always presented as a necessary consequence of the theory of evolution.

Convinced of the “truth of the monistic philosophy,” Haeckel published a comprehensive statement of his beliefs in 1899 under the title Die Welträthsel. The book is divided into sections on anthropology (man), psychology (the soul), cosmology (the universe), and theology (God). The great success of this work, which was translated into many languages, was the result of the situation around 1900. Haeckel’s attempt to establish a Weltanschauung in harmony with the advances of science answered a contemporary need. On the other hand, his harsh attack on church dogma and his often insecurely grounded generalizations led to heated controversies with scientists, theologians, and philosophers. On many occasions his rash statements were exploited to cast doubt on the validity of the theory of evolution. Typical in this regard was the controversy over Haeckel’s far too schematized illustrations of various embryonic stages. Concerning these “forgeries,” many distinguished anatomists and zoologists (including Theodor Boveri, Alexander Goette, Karl Grobben, Richard Hertwig, and Weismann) explained in 1909 that while they did not approve of Haeckel’s methods, they nevertheless refused to attack him, since the concept of development “cannot suffer any damage through some incorrectly rendered embryological illustrations.”

The nature of Haeckel’s participation in the battle over concepts of development also affected his account of the prehistory of Darwinism. His historical sketches are characterized by a passionate defense of Lamarck, while Darwin severely criticized the latter’s theory on many occasions.⁵ According to Haeckel, Lamarck’s Philosophie zoologique (1809) was “the first systematically founded presentation of the theory of the origin of species” and the first to “openly draw all its consequences”; it represented, moreover, “the beginning of a new period in the intellectual evolution of mankind.” He thought that the reasons for Lamarck’s failure lay above all in the authority of Georges Cuvier.

This view led Haeckel to make a series of misjudgments that, through his popular writings, were influential until recently. Among these was his judgment of the controversy between Étienne Geoffroy Saint-Hilaire and Cuvier at the French Academy of Sciences in 1830, which was “essentially over the theory of transformism.” Haeckel interpreted Cuvier’s catastrophist theory as a dogmatic theory of the absolute constancy and independent creation of species, although Cuvier himself did not take up these issues. Equally incorrect was Haeckel’s interpretation of Goethe’s writings on comparative anatomy and botany in terms of the theory of evolution.

Haeckel’s enthusiastic defense of Lamarck can be understood from similarities in the two men’s scientific careers, in their methods, and in their fixed goals. Both came to zoology from botanical systematics, and as zoologists both specialized in the systematics of the invertebrates. Both further employed the “natural system” of recent organisms to demonstrate phylogenetic relationships. Both were preoccupied by the religious and philosophical aspects of evolutionary theory. On the other hand, the differences between Haeckel and Darwin with regard to methods and argumentation are evident.

Haeckel’s artistic endeavors were characteristic of him. During his many trips he produced numerous watercolors and vivid descriptions of his travels that are still charming. His Kunstformen der Natur (1899–1904) corresponded to his “monistic religion” with its three “cult ideals of the True, the Good, and the Beautiful.”

Haeckel’s historical importance consists principally in his suggestions that stimulated further work. His spirited advocacy of Darwin’s ideas—not all of which he agreed with—contributed to the breakthrough of evolutionary thinking in the construction of biological theories. Moreover, concepts that Haeckel was the first to formulate, such as ontogeny, phylogeny, ecology, and chorology, have been adopted.

Haeckel—unlike Gegenbaur—did not form a school. Nevertheless, he did inspire many students (including Anton Dohrn, Richard and Oscar Hertwig, Arnold Lang, Hans Driesch, and W. Kükenthal) to take up zoology, especially research on marine animals. Yet these students early chose their own paths. In fact Haeckel scarcely participated in the development of modern experimental zoology that was then under way.

The characteristic elements of Haeckel’s lifework were already evident in 1866 in his Generelle Morphologie. His striving for a scientifically based world view led him to statements on philosophical, political, and religious questions in which he advocated dubious conceptions drawn from social Darwinism. In this enterprise Haeckel was responding to the demands and needs of his time, which explains his work’s success. Yet his lasting contribution lies not in the solutions he proposed but rather—and this is particularly true of his writings on the theory of evolution—in the questions he raised.

NOTES

1. Haeckel’s herbaria are now in the Ernst Haeckel House and in the Haussknecht Herbarium of Friedrich Schiller University, Jena.

2. Haeckel wrote about this at length in his letters to his parents (1852–1856). In the summer semester of 1856 he was Virchow’s assistant in Würzburg. They became friends at this time and remained on good terms until 1877, when Virchow publicly criticized certain of Haeckel’s conceptions and suggestions (such as the teaching of Darwin’s theory in the schools).

3. In 1863 August Schleicher had addressed an “Offenes Sendschreiben” to Haeckel entitled “Die Darwinsche Theorie und die Sprachwissenschaft.”

4. Haeckel inferred the phylogeny of the olynthus from its ontogeny. The individual embryonic stages corresponded to the “original [phylogenetic] conditions.” Thus he compared what he termed the “morula” stage with and amoeba colony (Synamoeba). According to Haeckel, the gastrula developed from the morula after passing through the “planula” stage.

5. Letter to J. D. Hooker of 11 Jan. 1844: “Heaven forfend me from Lamarck nonsense of a ‘tendency of progression,’ ‘adaptions from the slow willing of animals,’ etc.!” Revealing also are the letters to Lyell of 11 Oct. 1859 and 12 Mar. 1863, in Francis Darwin, ed., Life and Letters of Charles Darwin (London, 1887).

BIBLIOGRAPHY

I. Original Works. Haeckel’s most important writings are Die Radiolarien (Rhizopoda radiaria) (Berlin, 1862); Generelle Morphologie der Organismen, 2 vols. (Berlin, 1866); Natürliche Schöfungs-Geschichte (Berlin, 1868); Anthropogenie oder Entwickelungsgeschichte des Menschen. Keims-und Stammes-Geschichte (Leipzig, 1874); “Die Gastraea-Theorie, die phylogenetische Classification des Thierreichs und die Homologie der Keimblätter,” in Jenaishce Zeitschrift für Naturwissenschaft, 8 [n.s. 1 ] (1874), 1–55; “Die Gastrula und die Eifurchung der Thiere,” ibid., 9 [n.s. 2 ] (1875), 402–508; Systematische Phylogenie, Entwurf eines natürlichen Systems der Organismen auf Grund ihrer Stammesgeschichte, 3 vols. (Berlin, 1894–1896); Die Welträthsel. Gemeinverständliche Studien über monistische Philosophic (Bonn, 1899); Fünfzig Jahre Stammesgeschichte. Historisch-kritische Studien über die Resultate der Phylogenie (Jena, 1916); and Kristallseelen. Studien über das anorganische Leben (Leipzig, 1917).

Haeckel’s extant MSS are in the Institute for the History of Medicine and Science, Ernst Haeckel House, Friedrich Schiller University, Jena.

II. Secondary Literature. On Haeckel or his work, see Gerhard Heberer, ed., Der gerechtfertigte Haeckel (Stuttgart, 1968); Johannes Hemleben, Ernst Haeckel (Reinbek, 1964); Heinrich Schmidt, ed., Was wir Ernst Haeckel verdanken (Leipzig, 1914); and Ernst Haeckel. Denkmal eines grossen Lebens (Jean, 1934); Georg Uschmann, Geschichte der Zoologie und zoologischen Anstalten in Jena 1779–1919 (Jena, 1959); and “Über das Verhältnis Haeckels zu Lamarck und Cuvier,” in Medizingeschichte unserer Zeit (Festschrift Heischkel-Artelt) (Stuttgart, 1971), pp. 422–433; Georg Uschmann and Bernhard Hassenstein, “Der Briefwechsel zwischen Ernst Haeckel und August Weismann,” in Kleine Festgabe aus Anlass der hundertjährigen Wiederkehr der Gründung des Zoologischen Institutes der Friedrich-Schiller-Universität Jena (Jena, 1965), pp. 6–68; and Georg Uschmann and Ilse Jahn, “Der Briefwechsel zwischen Thomas Henry Huxley und Ernst Haeckel,” in Wissenschaftliche Zestschrift der Friedrich-Schiller-Universität Jena, Math-naturwiss. Reihe, 9 (1959–1960), 7–33.

Georg Uschmann