AASP – The Palynological Society

Promoting the scientific understanding of palynology since 1967

Hundredth year memorium: Christian Gottfried Ehrenberg 1795-1877. Palynology 2: 209-211 (1978)

SARJEANT, W.A.S.
Department of Geological Sciences
university of Saskatoon
Saskatchewan S7N OWO

It was in the year 1837 that scientists were first made clearly aware of the immense abundance of microfossils. This came about through the presentation to the Berlin Academy of Sciences, on the 20th July, of a paper in which it was convincingly demonstrated that large masses of rock, whole strata, might be made up entirely of the fossilized remains of organisms too small to be distinguished by the naked eye. To the nineteenth-century scientific public, this seemed a fascinating paradox. Many of them had purchased microscopes for serious research or as drawing-room toys; and soon they were busy looking at powdered rock debris and polished rock slices, to see these remarkable objects for themselves.

The microscopist who had reported this discovery was already a renowned figure in the German scientific world. Christian Gottfried Ehrenberg had been born on 19th April 1795 at Delitzsch, in the Electorate of Saxony (then an independent state). After commencing medical studies in nearby Leipzig, he transferred in 1817 to the University of Berlin in the Kingdom of Prussia; Berlin was thereafter to be his home. He took his degree in 1818, presenting a thesis describing 250 species of fungi from the Berlin district, of which sixty-two were new to science. He was later to make original observations on the process of reproduction in fungi and to observe the process of cryptogamous reproduction in molds, thus making the first of many contributions to the refutation of the old theory of spontaneous generation of these "lower" organisms.

At this time, the world was wide open to scientific exploration, with the faunas and floras of whole continents still waiting to be described. Ehrenberg and a friend of student days, Wilhelm F. Hemprich, decided to team up for such a journey. They made plans to travel to Madagascar; but, because of Ehrenberg's acceptance of a temporary botanical appointment at the University of Konigsberg, the journey was postponed and ultimately never took place. Instead the two friends attached themselves as naturalists to an archaeological expedition to Egypt, finances being found for this by the Prussian Academy of Sciences. The expedition proved disastrous. It was from the outset poorly organized and inadequately financed; and its leader, Count Heinrich von Menu von Minutoli, seems to have entirely lacked the skill and diplomacy requisite in such a task. After an early foray from Alexandria to Cyrenaica and the oasis of Ammon had ended in disorder, the expedition returned to a fever-stricken Alexandria and effectively collapsed, several of its members dying there. Hemprich and Ehrenberg hastily left the city, heading south into the Fayum; and, though Ehrenberg had already contracted typhus, Hemprich was able to nurse him back to health in the drier, cleaner desert air of Sakkara.

The subsequent wanderings of the two scientific travelers are an odyssey yet to be fully recounted. They traveled south down the Nile valley to the Nubian province of Dongola. While Hemprich took the material they had collected during this journey back to Alexandria, Ehrenberg, who had made friends with the local Pasha, continued studying the natural history of this region, in particular making studies of the microorganisms in the local waters which presaged much of his later work. On Hemprich's return, they journeyed together back to Alexandria. No further funds had arrived from Prussia and for a while it seemed their journeying must end; but eventually the Austrian consul furnished them with money for a second journey. This time they traveled east into the Sinai Peninsula and to El Tur on the Red Sea. Here Ehrenberg stayed behind again, this time to undertake studies of corals and medusae while Hemprich again took their collections back to Alexandria. Hemprich again encountered financial problems and Ehrenberg had to undergo five months of privation and anxiety before his friend rejoined him. Thereafter the two traveled on through Syria and Lebanon to Ba'labakk (Baalbek), making rich botanical collections. Hemprich almost succumbed to a snakebite, but survived to return for a fourth and last time to Alexandria.

Once again the Austrian consul was forthcoming with funds; and the two friends, their appetite for adventure unabated, returned to El Tur and took ship south down the Red Sea, calling at several points on the coast, visiting the Dahlak Archipelago and the Farasan Islands and landing at Juddah (Djedda) in Arabia to make a hurried journey to Mecca. Eventually they landed at Massawa in what is now Eritrea, intending to travel inland to Abyssinia; but by then the long journey had taken such toll of Hemprich's health that he succumbed to typhus. He was buried on one of the Red Sea islands. Ehrenberg had no heart to continue on alone; he took ship north again to the Egyptian port of Quseir (Kosseir) and crossed the desert by camel to El Gtza (Gizeh), himself ill with fever during much of what must have been a nightmare journey. After packing up his specimens, he voyaged back to Trieste, landing in December 1825 after five years of travels. He was the last survivor of the von Minutoli expedition.

Even then Ehrenberg's troubles were not over, for he had to undergo prolonged quarantine before being allowed to return to Berlin. Hemprich and he had accumulated a vast and valuable collection; around 34,000 zoological and 46,000 botanical specimens, specimens of some 300 rock types, some archeological and ethnographical material and many geological and topographical maps and sketches; altogether the collections filled 114 crates. During the quarantine, some of the boxes were damaged and their contents so destroyed or disarranged that it later proved impossible to make sense of them. Some living plants forwarded to Berlin from Trieste were killed by frost en route and unauthorized sales of some of the material further decimated the collection. This series of mischances following his friend's death must certainly have adversely affected Ehrenberg's enthusiasm for continuing research on his Middle Eastern material. Although Ehrenberg published a plan of work on the collections and the first installment of an account of his travels, neither task was ever to be completed.

Within a year of his return, Ehrenberg instead set out on a second major journey, across Russia. This expedition was led by his friend Alexander von Humboldt and undertaken at the invitation of the Czar; a third member was the mineralogist Gustav Rose. This time Ehrenberg's task was primarily to serve as botanist, though of course he took along his microscope too. The three scientists went via St. Petersburg and Moscow to Nizhni Novgorod (now Gorki), up the Volga to Kazan and Ekaterinenburg (now Sverdlovsk) and then to the northern Urals and the western slopes of the Altai, returning through Astrakhan and down the Volga to the Caspian Sea, where Ehrenberg studied plankton. The journey took eight months. In 1831, Ehrenberg married Gustav Rose's niece Julie; they were to have one son and four daughters before her death in 1848.

On return, Ehrenberg resumed for a while the task of studying his Middle Eastern collections. During his travels he had observed the growth of fertilization tubes from pollen grains of Stapelia; he was probably the first to observe this phenomenon, but the results were published belatedly and the priority of discovery was claimed by other scientists. His studies of the physiology of Red Sea corals and medusae were of lasting importance; and he also made dissections and drawings of molluscs, echinoderms and electric rays, embryological studies of insects, crabs and spiders, and notes on vertebrate ectoparasites. However, the bulk of discoveries resulting from those vast collections were left to be made by others; nor did Ehrenberg ever publish any notes on the plant collections he had made in Russia.

Instead, it was in his microscopical studies that Ehrenberg was to make his most lasting contributions to science. Although unicellular organisms had been discovered in the very earliest days of microscopy by Antoni van Leeuwenhoek, they had subsequently attracted only intermittent study and were still very poorly understood. During his travels Ehrenberg had studied the microorganisms in many different waters the River Spree, the Mediterranean, the Nile, the Red Sea, and the rivers of Russia and the Sudan. He had been impressed by the fact that, though varied in form, there was an overall unity in the character of the microbiota of these different waters, sufficient unity indeed for him to begin to formulate an overall classification for them. In addition, he had been impressed by the structural complexity of these minute beings, these "animalcules" or "Infusoria". Many scientists of his time believed that unicellular organisms had an "atom or monadlike" simplicity of structure, but Ehrenberg found their construction to be in reality extremely complicated and showed that they performed all the basic functions of higher organisms movement, feeding, excretion, reproduction. In 1838 his ideas were presented in a monograph whose very title stresses this interpretation Die Infusoriensthierchen als volkommene Organismen, "the Infusoria as complete organisms."

He was later to carry these ideas rather too far, coming to believe in the presence of complete systems of organs nervous and digestive in unicellular animals and attempting to maintain a classificatory unity between unicellular and multicellular organisms that cannot now be considered justified. These misconceptions were reinforced by his strange refusal to use microscopical magnifications greater than X300 in his studies; and unquestionably these erroneous assumptions greatly hindered his acceptance of Darwinian evolutionary theories.

Nevertheless, Ehrenberg's establishment of a first classification for the Infusoria was a major step forward in biology; and it enabled him to embark with confidence on the studies of their remains in sediments and rocks. In the fields of micropaleontology in general and of palynology in particular, he ranks as one of the greatest pioneers. During studies of chalks and limestones from Egypt, Syria, Sicily and Pomerania (Germany), he gave the first descriptions of coccoliths and showed that these minute organic platelets, along with the shells of foraminifera, are so immensely abundant as to actually make up those strata. Examining thin flakes of Jurassic chert and Cretaceous flint, he discovered what he considered to be the fossilized remains of motile dinoflagellates, noting also some spinose bodies which he described as "xanthidia" and which later came to be called "hystrichospheres"; we now know that both his supposed motile forms and his "xanthidia" are in fact dinoflagellate cysts. He also discovered, in Tertiary marine sediments and diatomites, the first remains of the internal siliceous skeletons developed by some dinoflagellates the only remains of motile dinoflagellates yet discovered in the fossil record. Studying soils from Brazil and other parts of America, he gave the first descriptions of plant phytoliths, minute "trace-fossils" that have still not attracted adequate study; and he contributed immensely to knowledge of other groups of microfossils diatoms, radiolaria, foraminifera, ostracods, spores and many others. His huge book Mikrogeologie (1854) contains illustrations of a greater variety of microfossils, known or then unknown, than have ever subsequently been assembled within the covers of a single work.

His investigations ranged very widely, embracing everything from the waters and sediments of ponds and rivers to deepsea samples, collected at depths of up to 12,000 feet on the early oceanographic expeditions, from soils to sedimentary rocks, from specimens he collected himself in walks around Berlin to samples sent by others from the ends of the earth. He was one of the first to study the dissemination of cysts and spores of unicellular and multicellular organisms by the wind, thus furnishing another plank for the coffin of the spontaneous-generation theory. He demonstrated that dust-storms and colored rains in southern Europe, hitherto unexplained, were the product of strong winds from the Sahara; and he showed how marine phosphorescence could be caused, and marine waters and snows ("red tides" and "blood-snows") given color, by the presence of microorganisms. All in all, he established himself as the foremost microscopist of his day, receiving many scientific honors. In 1857 Ehrenberg was fittingly the first recipient of the Leeuwenhoek Medal awarded by the Amsterdam Academy of Sciences.

Though Ehrenberg never created a scientific school, his studies aroused great interest not only in Berlin but also in other countries he visited; Denmark, Norway and Sweden in 1833, Italy in 1845, England and Ireland in 1847. He made friends readily and was an admirable correspondent. His receipt of so many specimens from other countries was a consequence of this: Darwin, Hooker, Edward Forbes, Dana, Silliman and Hitchcock were among the many who sent him material for study.

In 1852 he married his second wife, Karolina Friccius; and three years later he was elected Vice-Chancellor of the University of Berlin, where he also served for four periods as Dean of the medical faculty. His activities were greatly curtailed by a fractured femur in 1864; and, during the long spells in bed that followed, his eyesight began to deteriorate. However, a cataract operation in 1867 partially restored his sight and, with the assistance of his younger daughter Clara, he managed seven more years of fruitful work before further deterioration of his sight finally ended his researches. He died on 27th June 1876.

It is fitting indeed that this Association should dedicate its Annual Meeting, in the centenary year of Ehrenberg's death, to the memory of this great scientist.

References Cited

  • Hanstein, J. 1877. Christian Gottfried Ehrenberg. Ein Tagwerk auf dem Felde der Naturforschung des 19 Jahrhunderts. Bonn: Adolph Marcus, viii + 162p., port.
  • Humboldt, A. von 1826. Bericht uber die Naturhistorischen Reisen der Herren Ehrenberg und Hemprich durch Agypten, Dongola, Syrien, Arabien und den ostlichen Abfall des Habessinischen Hochlandes, in den Jahren 1820-1825. Abh. preuss, Akad. Wiss., Berlin, pp. 1-26.
  • Jahn, I. 1971. Ehrenberg, Christian Gottfried. In C. C. Gillispie (ed.) Dictionary of Scientific Biography, IV, pp. 288-292.
  • Koehler, O. 1943. Christian Gottfried Ehrenberg, 1795-1876. In H. Gehrig (ed.) Schulpforta und das deutsche Geisteleben. Darm- stadt: Buske, pp. 58-68, 2 ports.
  • Stresemann, E. 1954. Hemprich und Ehrenberg. Reisen zweier naturforschen- der Freunde im Orient geschildert in ihren Briefen aus den Jahren 1819-1826. Abh. dt. Akad. Wiss. Berlin, Kl. Math ailgem. Naturwiss., Jg. 1954, 1, pp. 1-177.
  • Wetzel, O. 1966. Christian Gottfried Ehrenberg, I795-1876. In K. Freund and A. Berg (eds.) Geschichte der Mikroskopie: Leben und Werk grosser Forscher, vol. III, Angewandte Natur- wissenschaften und Technik. Frankfurt-am-Main: Um- schau Verlag.

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