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History of Ecological Sciences, Part 47: Ernst Haeckel's Ecology

2013; Ecological Society of America; Volume: 94; Issue: 3 Linguagem: Inglês

10.1890/0012-9623-94.3.222

2327-6096

Frank N. Egerton,

American Environmental and Regional History

Click here for all previous articles in the History of the Ecological Sciences series by F. N. Egerton Ernst Haeckel, one of the world's best-known and most-read zoologists, named and defined a new science, "Oecologie" (1866, II:286). Was he, therefore, an ecologist? Robert Stauffer (my dissertation advisor) said yes (1957), but wrote that what was good in his ecology he got from Darwin, and what was misguided, he got from himself. There is some truth to that, but the story is more complex. (Stauffer was more interested in Darwin than Haeckel.) Haeckel had already absorbed Alexander von Humboldt's ecological perspective long before he read Darwin's Origin, though Humboldt's ecology lacked Darwin's concept of competition. If Haeckel is accepted as one founder of ecology, ecologists will want to know why he remains a controversial figure and how to evaluate the controversies. An introduction to these matters follows at the end. One, arranged on official lines, offered to the sympathetic observer all the species in "typical" specimens, as radically distinct forms, each decked with its pretty label; the other was a private collection, only shown to one trusted friend, and contained only the rejected kinds that Goethe so happily called "the characterless or disorderly races [Geschlechter], which we hardly dare ascribe to a species, as they lose themselves in infinite varieties,"… In this a large number of specimens arranged in a long series, illustrated the direct transition from one good species to another. …among the seaweed there were to be found many of the dearest little animals, specially charming polyps (Tubularia, Eudendrium, Actinia), sea spiders (Pycnogonum littorale), and a very strange member of the tunicata (Amaraecium rubicundum)… we saw a few seals at no great distance from us … The strangest thing we caught was a beautiful green garpike (Belone vulgaris) with green bones, and I have been sitting all day examining the highly peculiar ova under the microscope; besides that we caught swimming crabs, a few shrimps, which are very scarce here, sea devils (Cottus scorpius), sprats, a quantity of different plaice and haddock (torsk), together with other fish. In 1855 Haeckel published his first article in an important new journal edited by Müller (Richards 2008:40). In summer 1856, he accompanied Professor Albert Kölliker to Nice, France, where he found the marine fauna both rich and remarkable (Haeckel 1923:416). He wrote a doctoral dissertation on histology of river crayfish. He returned home to Potsdam in 1858, with an M.D., to practice medicine, and hated it. He spent 1859–1860 in Italy, studying marine life. … what high esteem and profound respect I hold the discoverer of the "Struggle for life" and of "Natural selection". Of all the books I have ever read, not a single one has come even close to making such an overpowering and lasting impression on me, as your theory of evolution of species. In your book I found all at once the harmonious solution of all the fundamental problems that I had continually tried to solve ever since I had come to know nature as she really is. Since then your theory—I can say so without exaggeration—has occupied my mind every day most pressingly, and whatever I investigate in the life of humans, animals or plants, your theory of descent always offers me a harmonious solution to all problems, however knotty. Thus began a warm friendship that lasted the rest of Darwin's life (Gliboff 2008:155–188). Ernst Haeckel in 1860. [Wikipedia] In 1861 Haeckel published part of his research to qualify for appointment to the faculty of Jena University. He owed the position to Carl Gegenbaur (1826–1903), whom he had known at Würzburg. Gegenbaur became his closest friend and collaborator (Nordenskiöld 1928:499–503, Uschmann 1959:27–33, Coleman 1978). Aside from numerous journeys, Haeckel spent the rest of his life at Jena. In 1862, he was promoted to associate professor and Director of the Zoological Museum, and on 18 August he married his cousin, Anna Sethe (1835–1864)—the great love of his life—who died a year and a half later, on Haeckel's 30th birthday. He continued studying specimens collected in Italy, which led to his monograph, Die Radiolarien 1862; the impressive illustrations in it, which he drew, undoubtedly helped win a gold medal from the Leopold-Caroline Academy. In this work, he speculated on species relationships and genealogy and continued doing so for the rest of his life (Wilson and Doner 1937:57– 58). He sent Darwin a copy. Darwin had already seen Huxley's copy, and Huxley sent Haeckel an enthusiastic letter and some specimens (Di Gregorio 2005:72–73). … constituted the first attempt to apply the general doctrine of development to the whole range of organic morphology (Anatomy and Biogenesis), and thus to make use of the vast march onwards which the genius of Charles Darwin has effected in all biological science by his reform of the Descent Theory and its establishment through the doctrine of selection. Radiolaria. Haeckel 1899–1904. Lithographer Adolf Gilitsch transformed Haeckel's sketches into forms with somewhat exaggerated colors. Every group of organisms that Haeckel studied became grist in his theoretical mill: he had a good command of Greek and coined many terms from Greek roots, including oecologie, phylum, ontogeny, phylogeny, and protista. He pioneered the construction of phylogenetic charts that indicated which groups of species were most closely related, and their likely ancestors (Dayrat 2003). He thought radiate rhizopods were the lowest level of animals, and so proper subjects for discussing the relationships between plants and animals. He coined the terms protista for all unicellular organisms. Other zoologists offered other names, but Haeckel's has stuck (Rothschild 1989:282–291). He also formulated a biogenetic law (ontogeny recapitulates phylogeny), which was a useful hypothesis to investigate. However, as a Haeckelian pronouncement it went too far and elicited far more disagreement than agreement (Churchill 1980, Rinard 1981, Rasmussen 1991). He provided a chart showing how to organize zoology, with ecology and animal geography placed under a broader heading of Animal Physiology. By ecology, we mean the whole science of the relations of the organism to the environment including, in the broad sense, all the "conditions of existence." These are partly organic, partly inorganic in nature; both, as we have shown, are of the greatest significance for the form of organisms, for they force them to become adapted. Among the inorganic conditions of existence to which every organism must adapt itself belong, first of all, the physical and chemical properties of its habitat, the climate (light, warmth, atmospheric conditions of humidity and electricity), the inorganic nutrients, nature of the water and of the soil, etc. As organic conditions of existence we consider the entire relations of the organism to all other organisms with which it comes into contact, and of which most contribute either to its advantage or its harm. Each organism has among the other organisms its friends and its enemies, those which favor its existence and those which harm it. The organisms which serve as organic foodstuff for others or which live upon them as parasites also belong in this category of organic conditions of existence. In our discussion of the theory of selection we have shown what enormous importance all these relations have for the entire formation of organisms, and specially how the organic conditions of existence exert a much more profound transforming action on organisms than do the inorganic. The extraordinary significance of these relations does not correspond in the least to their scientific treatment, however. So far physiology, to which this [science] belongs, has, in the most one sided fashion, almost exclusively investigated the conserving functions of organisms (preservation of the individual and the species, nutrition, and reproduction), and among the functions of relationship [investigated] merely those which are produced by the relations of single parts of the organism to each other and to the whole. On the other hand, physiology has largely neglected the relations of the organism to the environment, the place each organism takes in the household of nature, in the economy of all nature, and has abandoned the gathering of the relevant facts to an uncritical "natural history," without making an attempt to explain them mechanistically. This indubitable and highly important fact is revealed most strikingly in the tendency on average for the absolute number of organic individuals populating our world to remain constant, and for only the relative numbers of the individual species to alter continually in relation to each other. . . . yet Chorology as a whole remained, as far as their labours were concerned, only a desultory knowledge of a mass of individual facts. It could not be called a science as long as the causes for the explanation of these facts were wanting. These causes were first disclosed by the theory of selection and its doctrine of the migrations of animal and vegetable species, and it is only since the works of Darwin and Wallace that we have been able to speak of an independent science of Chorology. Monophyletischer Stammbaum der organismen. The first phylogenetic chart for the evolution of life. Haeckel 1866, II: plate 1. In other words, animal geography could tell us that Darwin's finches on different Galápagos Islands were different species, but not tell us why. Biologists have accepted his new science of ecology but have not considered his chorology a new science. Some biologists adopted Haeckel's term, but most simply added Darwin's new explanations to the preexisting science of biogeography. Ernst Haeckel and Nikolai Miklucho-Maklai, one of three student assistants who joined Haeckel's private expedition to the Canary Islands, 1866. Ernst-Haeckel-Haus, Friedrich-Schiller-Universität, Jena, Germany. By ecology we mean the body of knowledge concerning the economy of nature—the investigation of the total relations of the animal both to the inorganic and to its organic environment; including, above all, its friendly and inimical relations with those animals and plants with which it comes directly or indirectly into contact—in a word, ecology is the study of all those complex interrelations referred to by Darwin as the conditions of the struggle for existence. Still dissatisfied with the progress of his reform, in 1906 he published a one-volume abridgement of Generelle Morphologie. Repetition and a clear definition possibly helped establish his term, oecologie, for there were alternative suggestions available (Schurig and Nothacker 2001). In 1907 he established a Phyletisches Museum at the university, partly financed with royalties from his books (Uschmann 1959:165–175, Di Greogorio 2005:526–527). When his successor as director of the museum did not run it as Haeckel had expected, he turned his home into a museum—Ernst Haeckel-Haus (photos of both buildings in Smit 1967 and Richards 2008). The first general survey of animal ecology was not by Haeckel, but by Würzburg professor of zoology Karl Gottfried Semper (1832–1893), who had been a student there during some of the time that Haeckel was (Mayr 1975). Semper spent the period December 1857–May 1865 exploring the Philippines and Palau, and afterwards published Reisen im Archipel der Philippinen (10 volumes, 1868–1905; see Johnson 1969). In 1877 he delivered 12 lectures at Lowell Technological Institute in Boston, then prepared them for publication in both German (1880) and English (1881). His Animal Life as Affected by the Natural Conditions of Existence never used Haeckel's term oecologie. He could hardly have been ignorant of Haeckel's Generelle Morphologie, which aspired to reorganize zoology. One Haeckel biographer (Di Gregorio 2005:292) characterized Semper as "a dangerous enemy because he saw with remarkable insight which aspects of the Gegenbaur-Haeckel partnership were due to one or the other of the partners and attacked them accordingly." One of Semper's attacks was entitled Haeckelismus in der Zoologie (1875, edition 2, 1876). Semper's preface to Animal Life dismissed talk about ontogeny and phylogeny as useless—without mentioning Haeckel. He did reprint a Haeckel drawing of a sponge, duly acknowledged (1881:342), and his explicit attack on Haeckel was relegated to a long end-note (1881:461–463). Semper accepted Darwin's theory; his aversion was Haeckel's dogmatic pronouncements (Di Gregorio 2005:293–296). Haeckel adequately defined the new ecological science; but did he also contribute to the substance of ecology? The explorations of Humboldt and Darwin permanently impressed Haeckel. He never explored on a government expedition (though using government funds), but while at Jena he took some 90 trips, in Europe (24 to Italy) or abroad (Bozzolato and Stolz 1993, Di Gregorio 2005:438, Breidbach 2006:205–209). He published accounts of some foreign journeys, which can be mined for observations comparable to those by his models, Humboldt and Darwin, in their travel books. Haeckel's books, based upon field journals and sometimes letters sent home, include Arabische Korallen 1876, Indische Reisebriefe 1882, Aus Insulinde: Malayische Reisebriefe 1901, Italienfahrt: Briefe an die Braut, 1859–1860 1921, Berg- und Seefahrten: 1857–1883 1923. Wallace's Malay Archipelago (1869, German edition, 1869) was a magnet, drawing both Haeckel, and later two of his students, to Indonesia (Hossfeld 2004). Landscape painting was a lifelong hobby, and Haeckel returned from journeys with numerous scenes of places visited, some of which appeared in his travel books. His only son, Walter, became a landscape painter who lived in Munich. Haeckel in Ceylon, 1882. Schmidt 1934: facing page 32. Since Ceylon (Sri Lanka) was a British colony, Haeckel's Indische Reisebriefe was translated into English (as A Visit to Ceylon, 1883). It will be our sample of his travel books. It would have been greatly enhanced by some of his artwork, and perhaps a map. However, it is buoyed up by his constant enthusiasm for what he found and his enjoyment of the scenery. It was a six-month expedition, although it took a month each for the journeys there and back, funded by the Weimar government, perhaps because he was director of the university zoology museum and would collect specimens and information for it. It was a good choice because Sri Lanka is a biodiversity "hot spot" (Groves and Manamendra-Arachchi 2009). He began planning for this trip at Easter 1881 and spent the summer learning oil painting, photography, use of gun, nets, and traps, and he departed with 16 trunks of equipment, including books and microscope (Haeckel 1883:6). He left Jena on 8 October by train to Trieste, and then by boat from Trieste to Bombay via the new Suez Canal. He had been to the Red Sea in March 1873 to study the marine life (the subject of his 1876 book), but that had not dampened his enthusiasm for "my beloved Medusae, which appeared in the mornings between nine and twelve, at first singly and then in swarms: blue Rhizostoma, rose-coloured Aurelia, and reddish-brown Pelagia" (Haeckel 1883:41). He obtained a bucket of seawater at night to study the phosphorescent creatures, finding that the majority were minute Crustacea, and the remainder were mostly Medusae, Salpae, and Annelidae, though the brightest was Pyrosoma. He spent much of the voyage writing descriptions of his treasures. November 8 was "the glorious and memorable day of my life when I first set foot in a tropical land, admired tropical vegetation, and gazed in astonishment at tropical life in man and beast" (Haeckel 1883:42), and he had only reached Bombay, where he spent a very pleasant week on the estate of a German couple. It helped that both the Europeans and natives wherever he went were warmly welcoming. Haeckel's enthusiasm for plants had never diminished just because he had become a zoologist, and his book actually devoted more space to describing plants than animals, simply because the plants stayed still while he looked and plucked (he carried a "tin" for them, presumably a vasculum). For 30 years he had dreamed of seeing what his heroes Humboldt and Darwin had written about the tropics, and the reality matched his expectations. He also saw brightly colored birds, butterflies, and lizards, but waited for Ceylon to collect them, as he would have to unpack his equipment. Details of his descriptions seem to indicate he was watching with one eye while writing with the other, and he still found time to paint scenery. Haeckel was as much tourist as Humboldt and Darwin had been on their longer expeditions, but that aspect of his book is omitted here, though his recording of demographic data (as they had) can be noted (Haeckel 1883:85–91). Unlike modern ecologists who write about the Third World, he thought Ceylon's 1250 square miles could support six or seven times its ~2,500,000 people. (Seven times that figure would be 17,500,000; the current population of Sri Lanka is over 21 million.) Ancient chronicles and village remains indicated that the northern half of Ceylon was more heavily populated 2000 years earlier than it was in 1881. Ceylon (now Sri Lanka). Map by John P. Wood. National Geographic 129, No. 4 (April 1966):454. After a week in Bombay he took a boat to Colombo, on the western side of Ceylon, where he spent a month in a suburb, at the mouth of the Colombo River. The mangrove vegetation was very interesting. The term referred to several genera and families—Rhizophora, Sonneratia, Somnitzera, Avicennia, etc.—that had more or less spherical bushy crowns six or eight feet high, with thick stems above many-branched roots rising from the water (Haeckel 1883:99–100). The roots retained mud and sand from the river and extended the land. Roots also caught corpses and organic matter, and mangrove thickets were sometimes feared as sources of fevers (before mosquitoes were discovered as the carriers of malarial parasites). Haeckel did not fear fevers where he stayed, because frequent storms washed away stagnant water. One Colombo host gave Haeckel several bird-catching spiders, Myale, which his host had seen chase small birds, Nectarinia, and small geckos, Platyaactylus (1883:107). Green parrots and large black monkeys eluded Haeckel's gun, but he did shoot a green lizard, Hydrosaurus salvator, over six feet long, sunning beside a ditch, which had a strong tail that could inflict wounds on assailants (Haeckel 1883:121–122). From hot Colombo Haeckel traveled by train to the capital, Kandy, in central Ceylon at 1500 feet elevation, and on to a nearby botanical garden, Peradenia, founded in 1819. Its second superintendent, George Henry Kendrick Thwaites (1812–1882) had spent 30 years compiling Enumeratio Plantarum Zeylandiae 1864, describing about 3000 vascular species (Desmond 1977:612). Haeckel's copy had been owned by a German collector, Nietner, who had died in Ceylon, and Nietner's widow had given the copy to Haeckel (1883:147–148). The current superintendent, Henry Trimen (1843–1896), who befriended Haeckel, estimated that Ceylon had at least 5000 vascular species (Desmond 1977:618). While the reefs at Tur are, for the most part, conspicuous for warm colouring—yellow, orange, red, and brown—in the coral gardens of Ceylon, green predominates in a great variety of shades and tones: yellow-green Alcyonia, growing with sea-green Heteropora, and malachite-like Anthophylla side by side with olive-green Millepora; Madrepora, and Astraea of emerald hue with brown-green Montipora and Maeandrina. Haeckel had earlier mentioned that "Ransonnet's fine work especially contains much valuable information as to the coral reefs of Galle" (1883:153), and he continued (Haeckel 1883:185): "Ransonnet had already pointed out (Haeckel 1883:134) how singularly and universally green prevails in the colouring of Ceylon." That coloring prevailed on land as well as at sea, with birds, lizards, butterflies and beetles being mostly various shades of green, though the examples Haeckel cited were aquatic. He explained it by natural selection (1883:185–186): "The less the predominant colouring of any creature varies from that of its surroundings, the less will it be seen by its foes, the more easily can it steal upon its prey, and the more it is protected and fitted for the struggle for existence." Haeckel employed four boatmen whom he paid 5 rupees a day, and paying more when they dived with a crowbar for coral chunks weighing 50–80 pounds. He had not attempted his own dives at the Red Sea, but did in Ceylon, and found it very rewarding to see marine life as it lived. However, "Never in my life have I been so gashed and mangled as after a few days of diving and coral fishing at Galle, and I suffered from the consequences for several weeks after" (Haeckel 1883:190), although he thought the experience was worth the pain. At Belligam he had available a government rest-house with four servants (in addition to his boatmen), and set up a satisfactory zoological laboratory, though there were no screens on the windows (Haeckel 1883:206–209). His surface net revealed many pelagic species similar to those of the Straits of Messina, Italy, but also new species. The Challenger Expedition had shown that oceanic species are more widespread than continental species (Haeckel 1883:220). Ceylon's heavy daily rains were great for land vegetation, but they also washed "large quantities of red earth into the sea, which clouds its waters on most parts of the coast; its saltiness is reduced, and that pure and transparent condition of the sea–water is destroyed, which is the first and indispensable condition of life for many marine creatures, especially those of the coast" (Haeckel 1883:221). The 20 cases of specimens collected at Galle and 30 cases at Belligam were a rich reward for all his troubles in obtaining them (Haeckel 1883:225), and he still had time for an expedition into the wild high country with Trimen, who made all the arrangements. Waterfall at Pangerango, Tjiburrum, Java. By Haeckel. Krausse 1984: inside front cover. Ceylon's tallest central mountains reached 7000–8000 feet elevation, and uplands covered about a quarter of the island. In 1817, much of it was home to elephants, bears, tigers, boars, elk, and primitive Veddah people, but in 1825 Governor Edward Barnes established a successful coffee plantation there, and in less than 20 years coffee planters cut and burned the forests and built more plantations. Soon, came "greedy" Golunda rats (Golunda elliotti), "mischievous" coffee-bugs (Lecanium coffeae), and parasitic fungus (Hemileja vastatrix). The response had been a switch to growing tea and Cinchona for quinine (Haeckel 1883:275–277). After touring plantations, Haeckel met Trimen at the resort Newera Ellia and they traveled south into wild country where primeval forest alternated with dry or marshy meadows, patenas. These grew so densely that mountain myrtle (Careya arborea) was the only tree that could occasionally find places to grow (Haeckel 1883:302–303). High plateaus had Nilloo shrubs (Strobilanthus sp.), which was the favorite haunt of the elephants that ate them. The forest contained climbing bamboo (Arundinaria debilis) that crept up the tallest trees and had long stems that hung down from tree branches (Haeckel 1883:309). Their explorations concluded at World's End, where the plateau ended at a 5000-foot cliff, and where Haeckel saw 10–12 wild elephants. He and Trimen then descended a steep, winding trail for five hours to the Black River, the second largest in Ceylon. Crocodiles had once been common, but had declined due to heavy river traffic (Haeckel 1883:324). There were still large lizards and turtles, abundant fish, and large butterflies. Gnats and mosquitoes were often a problem, but not in March. On the steamship back to Egypt, Haeckel arranged and completed his notes and sketches. In Egypt he realized that Egypt depended heavily on the date palm and Ceylon on the coconut palm, and he found the coconut palm more picturesque (Haeckel 1883:334). (Sometimes his comments were more Humboldtian than Darwinian.) 205. Symbiosis.—Very many Radiolaria, but by no means all members of this class, live in a definite commensal relation with yellow unicellular Algae of the group Xanthellae. In the Acantharia they live within the central capsule (Zooxanthella intracapsularis, ¶ 76), in the Spumellaria and Nassellaria, on the other hand, within the calymma but outside the central capsule (Zooxanthella extracapsularis, ¶ 90); in the Phaeodaria a special form of these symbiotic unicellular Algae appears to inhabit the phaeodium in the extracapsulum, and to compose a considerable portion of the phaeodellae (Zooxanthella phaeodaris, ¶ 90, or better perhaps Zoochlorella phaeodaris, ¶ 89). Undoubtedly this commensal life is in very many cases of the greatest physiological significance for both the symbionts, for the animal Radiolarian cells furnish the inquiline Xanthellae not only with shelter and protection, but also with carbon dioxide and other products of decomposition for their nutriment; whilst on the other hand the vegetable cells of the Xanthellae yield the Radiolarian host its most important supply of nutriment, protoplasm and starch, as well as oxygen for respiration. Hence it is not only theoretically possible, but has been experimentally proved, that for a long period in closed vessels of filtered sea-water, kept exposed to the sunlight; the two symbionts furnish each other mutually with nourishment, and are physiologically supplementary to each other by reason of the opposite nature of their metastasis. This symbiosis is not necessary, however, for the existence of the Radiolaria; for in many species the number of Xanthellae is very variable and in many others they are entirely wanting. Haeckel, Report on the Radiolaria collected by H.M.S. Challenger during the years 1873–1876. Volume 18, 1887, plate 99, drawn by Haeckel. [Linklater 1972:169] He then compared this symbiosis with that of lichens. Karl Brandt (1881), in Berlin, wrote on the algae that lived within invertebrates, and he named and discussed the genera Zooxanthella and Zoochlorella (Sapp 1994:11). The symbiosis concept originated in the work of Simon Schwendener (1869) on the relationship between algae and fungi in lichens, but it was botanist Albert Bernhard Frank who coined the term "Symbiotismus" in 1877, and botanist Anton de Bary used the term "Symbiose" in 1878 (Sapp 1994:4–7, Mitchell 2002). …that the whole method employed by Hensen for determining the plankton is utterly worthless, and that the general results obtained thereby are not only false, but also throw a very incorrect light on the most important problems of pelagic biology. Hensen replied that Haeckel was ideologically motivated and scientifically backward (Breidbach 1990:109–110, Di Gregorio 2005:448), and four historians of biology have condemned Haeckel's response (Stauffer 1957:141–143, Damkaer and Mrozek-Dahl 1980:465–466, Taylor 1980:516). Haeckel's skepticism motivated Hensen and other marine biologists to spend more time testing sampling methods than they might have without such skepticism (Porep 1972, Lussenhop 1974:331–337, Mills 1989:29–42, Breidbach 1990, Jahn 2000). Determining oceanic plankton abundance remained a difficult challenge well into the 1900s (Herman and Platt 1980). A collection of sea anemones. Haeckel 1899–1904. This magnificent new species of the genus Rhopilema, one of the most beautiful of the medusae, was captured on 10 March 1901 under the equator in the Malaccan Straits. It bears its name as a remembrance of Fräulein Frida von Uslar-Gleichen, the artistic friend of nature, who has advanced the "Kunstformen der Natur" in numerous ways by her exquisite judgment. Since neither was willing to end his marriage because of their mutual love, their relationship was mainly conducted through the mail—over 900 letters written between them (Elsner 2000). Less than a third of them were first published without either author's name (Werner 1927), and translated into English with his name listed and a pseudonym for her (Werner 1930). You asked recently what my friend Gegenbaur had said about the book [Die Welträtsel (1899, Riddle of the Universe)]. Up to now, not a word! He shares my views from first to last, but has always been of the opinion that these are esoteric mysteries to which the great public has no right; he too has always censured the sharp aggressiveness of my phraseology. By "he too has always censured …" Haeckel meant in addition to Frida's own complaints. Haeckel's son lent the correspondence with Frida to Werner to edit. This letter and the one quoted below are not in the Ernst-Haeckel-Haus archives today (Thomas Bach e-mail 19 July 2010); all of their existing correspondence is in the Elstner edition (2000). Either these two letters were lost after Werner edited them, or he filled in gaps with what he imagined Haeckel thought. Apparently, Die Welträtsel was the last straw for Gegenbaur, who was not the only professor unhappy with it (Di Gregorio 2005:512–513, Richards 2008:7). Haeckel never recovered from the loss of Gegenbaur's friendship. Both my beloved parents remained pious Christians in the best sense of the word to their death; and even I as a student up to my 21st year, clung ardently to the Church—faith that I loved—despite all the assaults of science. It was only when I had penetrated farther and farther into the mysteries of life and its evolution, when as a practicing physician I grew thoroughly familiar with all the misery of mankind, and as a student with all the grandeur of "godless" nature, that I became after the most desperate spirit