EIMER, THEODOR GUSTAV HEINRICH

(b, Stäfa, near Zurich, Switzerland, 22 February 1843; d Tübingen, Germany, 29 May 1898)

zoology.

Eimer’s father, Heinrich, was a political refugee from the aborted coup that in 1833 had attempted to dissolve the Diet of the German Confederation in Frankfurt. He escaped to Switzerland, where he practiced medicine in the town of Stäfa. There he met and married Albertine Pfenniger, who came from a prominent family of the area. In 1845 the family moved to Lahr, on the western edge of the Black Forest, which Theodor always considered his native town. Subsequently they lived in the Baden towns of Donaueschingen, Langenbrücken, and Freiburg, where Heinrich served as a regional physician.

Until the age of twelve, Eimer received private tutoring; thereafter he attended gymnasiums in Bruchsal and in Freiburg. Following in his father’s footsteps, he studied medicine. In 1862 he matriculated at Tübingen, where he was particularly influenced by the histologist Franz von Leydig. He then spent the year 1863–1864 at Freiburg and the year 1864–1865 at Heidelberg. After taking examinations in the natural sciences, Eimer returned to Tübingen for the winter semester of 1865–1866. Between 1866 and 1868 he worked in Rudolf Virchow’s laboratory in Berlin, receiving his medical degree in 1867. It was Virchow who turned Eimer from his original interest in anthropology to zoology. In early 1868 Eimer went to Karlsruhe to take his state medical examinations, then spent the next twelve months studying zoology at Freiburg under August Weismann. A three-month winter interlude in Paris rounded out his studies.

In 1869 Eimer was hired as prosector of zootomy (comparative anatomy) by Albert von Kölliker at Würzburg, where he received his doctorate for histological and experimental work on fat absorption in the intestine. On 18 July 1870 he married Anna Lutteroth, the daughter of a Hamburg banker, and the following day was habilitated in zoology and comparative anatomy. Immediately thereafter Eimer volunteered for military service as a field surgeon. He saw action at the siege of Strasbourg and was joined by his wife, who served as an army nurse. After being decorated for service, he was forced to retire from active duty because of illness. Early in 1871 the Eimers journeyed to Capri, where Theodor became familiar with marine organisms. He returned to the island in 1872, 1876, 1877, and 1879. The coelenterates of the Bay of Naples and the lizards of Capri formed the subjects of Eimer’s first book-length monographs in zoology.

In 1874 Eimer became the inspector of the grandduke’s collections in Darmstadt and associate professor of zoology at the Technische Hochschule. In 1875 he succeeded Leydig as a full professor of zoology and comparative anatomy at the University of Tübingen. Over the next twenty-three years Eimer developed and taught an array of courses in zoology with only a one-semester interruption. He was known for clear and lively lectures, and he attracted a coterie of loyal, even adulatory, advanced students. An invitation in 1888 to become the director of the Natural History Museum in Hamburg gave Eimer the leverage to convince the Württemberg minister to erect a new building for the zoological institute at Tübingen. He also promoted the study of veterinary medicine at Tübingen and persuaded the university to offer a doctorate in this subject.

From the beginning of his residence in Tübingen, Eimer participated vigorously in the affairs of the Württemburg Society for Natural History and of its Black Forest branch. In 1879 he became a member of the prestigious Leopoldina. Highly patriotic, Eimer was a leader of the Württemberg branch of the National Liberal party (Deutsch-Nationale Partei¹) until the mid 1880’s and continued to practice in a general clinic in order to be prepared to serve again as a military surgeon in the event of national mobilization.

The Eimers were fond of traveling during the summer. They often visited Italy, where Eimer worked at the zoological stations in Naples and Rovigno; they visited the Balkans, Constantinople, and the North and Baltic seas; and during the winter of 1878–1879 they traveled up the Nile as far as Nubia. In 1879 Eimer purchased a small estate near Lindau on Lake Constance, where he intended to spend vacations and to pursue zoological studies on the lake. He fell seriously ill during the fall semester but continued to perform his offical duties at the university until the following May, when he underwent an operation for a severe intestinal disorder. Eight days later, on 29 May 1898, he died at the age of forty-five. He was survived by his wife, two sons, and two daughters.

The first phase of Eimer’s scientific career was histophysiological in nature. Under the tutelage of Virchow he studied fat absorption in the small and large intestines. From 1872 to 1875 he studied the nucleus of the cell, but his microscopic technique was considerably inferior to that of Friedrich Anton Schneider, Eduard Strasburger, and Walther Flemming, who were in the process of transforming our knowledge of the nucleus. Eimer also studied the nature of the reptilian egg and made the minor discovery that sponges possess nematocytes and produce spermatozoa. His most important discovery during this period involved a description of the life cycle of a coccidian parasite (a spore-producing protozoan) in the mouse. This became a classic study that was often reproduced in textbooks; the genus of this particular coccidian was later named Eimeria by Schneider.

While on Capri during his convalescence of 1871 and again in 1872, Eimer began two series of investigations that were to reorient his biological interests. The first consisted of regeneration experiments with marine organisms. Beginning with the ctenophore Beroë and extending the investigation to the true jellyfish, Eimer amputated parts of the organism in order to determine the minimal center of activity of the primitive nervous system. With the medusae of the scyphozoans, he discovered that a single marginal sense organ, known as a lithocyst, was sufficient to initiate a rhythmic pulsation throughout the entire umbrella. He further discovered that a medusa with all the marginal lithocysts excised could gradually reorganize itself and develop new centers of stimulation.

Many of Eimer’s experiments paralleled and independently confirmed the contemporaneous physiological studies on the medusa’s nervous system done by George John Romanes. The philosophical implications of Eimer’s experiments, however, became clear only in 1883, when he delivered the address “Über den Begriff des tierischen Individuums” to the Versammlung der Deutschen Naturforscher und Ärzte in Freiburg. At that time he drew upon a range of nineteenth-century biological assumptions, including the biogenetic law, the principle of the division of labor, a recognition of the alternation of generations, and a belief in the inheritance of acquired characters, to question whether nature consisted of isolated organic individuals. With specific reference to the early-nineteenth-century Naturphilosoph Lorenz Oken, Eimer insisted that the individual merged into the species and that both implied “the totality of the animal kingdom.”²

The other series of investigations begun on Capri pursued the converse of this generalization. If the organic world consisted of a unity, why do we find separate species and individuals? The answer was found on the picturesque Faraglioni cliffs, which lie as isolated promontories jutting into the sea at the southeast end of Capri. There Eimer discovered a race of the common wall lizard (Lacerta muralis coerulea) that was markedly darker and bluer than the species on the rest of Capri and elsewhere. After comparing the unique race with members of the species throughout its European range. Eimer concluded that the environment, including selective pressures, interacted with chemically restricted internal growth patterns. “The inherited characters,” he explained, “produce the projected line [of development], the direction of which may be altered prior to or after birth only by the influence of the environment. For this resulting alteration can be nothing other than the necessary crystallization product of the changed makeup of the organism.”³ The isolation of the Faraglioni cliffs allowed the consequent changes to accumulate to form a separate race of wall lizard.

Eimer later extended his observations to the markings of birds, mammals, and especially butterflies. He consolidated his findings in Die Entstehung der Arten (1888–1901). In a highly speculative way, he argued that the formation of the organism was determined by the operation of four laws of growth: (1) that a directed evolutionary process is preceded by changes in the ontogeny of the individual; (2) that new characters first appear in the mature males and may be transmitted to the rest of the species through heredity—this is what Eimer called the law of male preponderance; (3) that these new characters usually appear at the posterior end or on the inferior side of the male and work their way forward and superiorly as the individual grows older (the law of wavelike development); and (4) that varieties are simply sequential stages in the development of the species.

It was the interplay of these growth patterns that explained for Eimer the division of nature’s unity into a multiplicity of forms. The local environment and other external factors, he argued, interacted with the constitution of an organism to render the peculiar characteristics of local varieties. These varieties advanced along particular lines of development while their neighbors remained static in an “Entwicklungsstillstand” or genepistasis. Speciation eventually followed. Eimer also explained atavism, degeneration, and saltations in phylogeny in terms of an environmental impact on local constitutions and the consequence growth patterns. He contrasted his mature evolutionary ideas with those Carl Naegeli presented in his Mechanisch-physiologische Theorie der Abstammungslehre (1884), for unlike Naegeli, Eimer did not invoke an internal perfecting principle to explain orthogenetic lines of evolution. He also distinguished his theory from the functionally oriented neo-Lamarckian movement, although he shared its commitment to the inheritance of acquired characters. Like the neo-Lamarckians, after 1883 Eimer found himself increasingly in direct conflict with the results of nuclear cytology and the neoDarwinian movement.

In his later researches Eimer concentrated on demonstrating the laws of development in butterflies. The results appeared in Die Artbildung und Verwundtschaft bei den Schmetterlingen (1888–1895), illustrated by his wife, which presented a detailed taxonomy of the worldwide genus Papilio (the swallowtails). Eimer used the longitudinal stripes on the wings to show that the changes from one species to another and from one subgenus to another consisted solely in minor alterations in the development of pigment in accordance with his developmental laws. His argument was based on his belief that such differences must reflect predetermined growth patterns rather than the useful traits required for the operation of natural selection. The wing patterns, which neo-Darwinians explained in terms of mimicry or protective coloration, were understood by Eimer in terms of similar growth patterns directed by slightly different external conditions.

As Eimer became more convinced of the correctness of his ideas, he became increasingly acerbic in his comments on the ideas of others. Weismann. the preeminent neo-Darwinian of the age, with whom Eimer had studied for a year in the late 1860’s and to whom he had dedicated a book of his experiments on medusae in 1878, became by the mid 1880’s the object of severe criticism in Eimer’s published works.

The thrust of Eimer’s lifework was to provide an explanation for evolution that did not rely on the utilitarian assumptions of natural selection. on functional adaptation, or on any vitalistic assumptions. Borrowing a term coined by Wilhelm Haacke in 1893, Eimer referred at the end of his life to his evolutionary explanation as “orthogenesis” or directional evolution. Orthogenesis was the subject of his major address delivered to the Congress of Zoologists at Leiden in 1895 and of his last book, Orthogenesis der Schmetterlinge, published a year before his death. Eimer remained adamant to the end that his evolution theory utilized only the physicochemical processes associated with his laws of growth.

NOTES

1. This name for Eimer’s political affiliation is given in Klunzinger’s obituary, but the author was unable to find a record of such a regional party. Klunzinger probably meant the Deutsche Partei, which was the Württemberg branch of the Nationalliberale Partei.

2. “On the Idea of the Individual in the Animal Kingdom,” 433.

3. Zoologische Studien auf Capri. II, Lacerta muralis coerulea (Leipzig, 1874), 42.

BIBLIOGRAPHY

I. Original Works. A complete bibliography of Eimer’s scientific writings is in Klunzinger’s obituary (see below). An expansion of his dissertation and his earliest papers on fat-absorbing goblet cells appeared in Virchow’s Archiv between 1867 and 1869; his microscopical studies on nuclear structure, on reptilian eggs, and on spermatozoa appeared in Archiv für mikroskopische Anatomie between 1871 and 1877. The first accounts of Eimer’s studies on ctenophores and observations on the Capri wall lizard were published as Zoologische Studien auf Capri. I. Über Beroë ovatus. Ein Beitrag zur Anatomie der Rippenquallen (Leipzig, 1873) and Zoologische Studien auf Capri. II. Lacerta muralis coerulea. Ein Beitrag zur Darwin’schen Lehre (Leipzig, 1874). His regeneration experiments on Beroë are described in “Versuche über künstliche Teilbarkeit von Beroë ovatus (angestellt zum Zweck der Kontrolle seiner morphologischen Befunde über das Nervensystem dieses Tiers),” in Archiv für mikroskopische Anatomie, 17 (1879), 213–240. Eimer’s address “Über den Begriff des tierisichen Individuums” is in the Amtlicher Bericht der Versammlung der deutschen Naturforscher und Ärzte for 1883 and in Humboldt. Monatschrift für die gesammten Naturwissenschaften, 2 (1883), 437–440. An English translation, “On the Idea of the Individual in the Animal Kingdom,” appeared as the appendix to Organic Evolution, 413–435 (see below).

The most elaborate discussion of Eimer’s laws of growth and their application to evolution is Die Entstehung der Arten auf Grund von Vererben erworbener Eigenschaften nach den Gesetzen organischen Wachsens. Ein Beitrag zur einheitlichen Auffassung der Lebenwelt, 3 vols. (Jena and Leipzig, 1888–1901). The first volume was translated by Joseph T. Cunningham as Organic Evolution as the Result of the Inheritance of Acquired Characters According to the Laws of Organic Growth (London and New York, 1890). Thesecond volume (1897), written with the assistance of C. Fickert, bore the secondary title Orthogenesis der Schmetterlinge, Ein Beweis bestimmt gerichteter Entwickelung und Ohnmacht der natürlichen Zuchtwahl bei der Artbildung, Zugleich eine Erwiderung an August Weismann. The third volume(1901), published posthumously by Fickert and Countess Maria von Linden, bore the secondary title Vergleichend-anatomisch-physiologische Untersuchungen über das skelett der Wirbeltiere. Whereas the first volume was published by Gustav Fischer of Jena, the second and third volumes were published by Wilhelm Engelmann of Leipzig.

Eimer presented further explication of the laws of growth with respect to swallowtails in Die Artbildung und Verwandtschaft bei den Schmetterlingen, 2 vols. and 2 atlases of 4 colored plates each (Jena, 1889–1895). The first volume bears the subtitle Eine systematische Darstellung der Abänderungen, Abarten und Arten der Segelfalter-ähnlichen formen der Gattung Papilio, the second volume the subtitle Eine systematische Darstellung der Abänderungen, Abarten und Arten der Schwalbenschwanzähnlichen Formen der Gattung Papilio. Fickert again assisted Eimer with the second volume.

Eimer’s Leiden address on orthogenesis, Über bestimmt gerichtete Entwicklung, Orthogenesis, und über Ohnmacht der Darwin’schen Zuchtwahl bei der Artbildung (Leiden, 1896), was reprinted as the first chapter of his Orthogenesis der Schmetterlinge, 1–49. An English translation appeared in book form as On Orthogenesis and the Impotence of Natural Selection in Species-Formation, Thomas J. McCormack. trans. (Chicago, 1898).

II.SECONDARY LITERATURE. There is no detailed study of Eimer’s life. The most important obituary is C. B. Klunzinger, “Theodor Eimer. Ein Lebensabriss mit Darstellung der Eimer’schen Lehren nach ihrer Entwickelung,” in Jahreshefte des Vereins für vaterländische Naturkunde in Württemberg, 55 (1899), 1–22, which provides a portrait, the most complete bibliography of Eimer’s publications, and a brief account of Eimer’s most important texts. Countess Maria von Linden, “Professor Dr. Theodor Eimer,” in Biologisches Zentralblatt, 18 (1898), 721–725, presents as a sketch of her former mentor’s personality and impact as a teacher. R. von Hanstein, in Leopoldina, 34 (1894), 107–108, is brief but contains useful information. Historian of biology Georg Uschmann wrote the standard account in Neue deutsche Biographie, IV (Berlin, 1959), 393–394.

Vernon L.Kellogg, Darwinism To-Day (New York, 1907), 281–285, presents a capsule summary of Eimer’s evolutionary ideas, contrasting them with other orthogenetic theories. A critical summary of Eimer’s evolution theory also appears in Yves Delage and Marie Goldsmith, The Theories of Evolution, André Tridon, trans. (New York, 1912, 1913), 298–302. While evaluating many contemporary evolutionary theories, Ludwig Plate describes elements of Eimer’s ideas throughout his Selektionsprinzip und Probleme der Artbildung, ein Handbuch des Darwinismus, 4th ed. (Leipzig and Berlin, 1913). Peter J. Bowler places Eimer’s biological accomplishments in the context of Weismann’s ideas and the reaction to them by some English and American biologists in “Theodor Eimer and Orthogenesis: Evolution by’ Definitely Directed Variation, ’” in Journal of the History of Medicine, 34 (1979), 40–73. See also Bowler’s The Eclipse of Darwinism. Anti-Darwinian Evolution Theories in the Decades Around 1900 (Baltimore and London, 1983), esp. 148–160. In both cases the analysis concentrates on Eimer’s few translated texts.

Frederick B. Churchill