Review Essay

DIE WERDENDE FORM. EINE GESCHICHTE DERKAUSALEN FORM. ACTA BIOHISTORICA.

SCHRIFTEN AUS DEM MUSEUM UNDFORSCHUNGSARCHIV FUR DIE GESCHICHTE

DER BIOLOGIE.By Reinhard Mocek

Basilisken Presse, Marburg an der Lahn, 1998,579 pp.

This monograph on the history of developmental bi-ology presents in nearly 600 pages three pioneers ofdevelopmental biology: the Swiss anatomist WilhelmHis (1831–1904), the German anatomist and develop-mental biologist Wilhelm Roux (1850–1924), and theGerman zoologist and natural philosopher HansDriesch (1867–1941). Mocek’s study is the impressiveoutcome of research done over 3 decades. Of course,there exist several very competent Anglo-Americanpublications dealing with the theoretical and historicalcontexts of morphogenesis. Thus, why does a distin-guished scholar such as Reinhard Mocek offer anothervoluminous study about such issues? The author re-sponds to this justified question that, up to now, welack historical and theoretical investigations whichconcentrate explicitly on causal morphology.

On first view, the answer will perplex historians ofbiology as anyone interested in the history of experi-mental embryology or morphogenesis. For, there werepublished studies by Jane Oppenheimer [1967, 1970],Jane Maienschein [1991], Lynn Nyhart [1987, 1995],Frederick Churchill [1973], Scott Gilbert [1991; Gilbertet al., 1996], Victor Hamburger [1988], Timothy Lenoir[1982], just to mention a few, during the last 20 years.However, Mocek has identified a weak point of histori-cal research on biology being until recently nearly ex-clusively pre-occupied with heredity and evolution. Noother work published in the last few years has workedout in such a detailed and learned way the completeworks (up to 1899) of His, Roux, and Driesch and hasextrapolated their conceptions to the most recent ap-proaches that try to link development and evolution.What distinguishes this study extending from His’ Un-tersuchungen uber die erste Anlage des Wirbelthier-leibes of 1868 to Driesch’s Die Lokalisation morphoge-netischer Vorgange of 1899 is the profound knowledgeof the author, the biotheoretical starting point, and fi-nally, the access of the native speaker to the program-matic texts of developmental biology of the 19th cen-tury, mainly written in highly dense German.

However, what remains that is substantial or evencontroversial concerning conceptions of the 19th cen-tury not previously discussed? For Mocek, the merits ofHis, Roux, and Driesch are that they undermined themono-causal thought pattern of Newtonian physics bytheir system-theoretical reasoning that always focusedon the wholeness of the living organism. Concretely,His countered the atomistic perspective of classical

morphology with his concept of organogenetic areas ofthe embryo (Prinzip der organbildenden Keimbezirke,1874). Roux talked about the molecular self-differentiation of the embryo, and Driesch defined theemerging form as a harmonious-equipotential system.With this outline, Mocek also specifies one main task ofhis study, namely, to elaborate the (bio)theoretical ba-sis for the actual research on morphogenesis and topoint out the connecting lines between evolutionary(phylogenetic) queries.

Thus, the objective here, although he does not stressit explicitly, is to inspect the (conceptual) progress ofthe biological sciences and to detect the continuity of abiotheoretical way of thinking from the 18th century tothe most recent self-organization theories of evolution.No doubt, such an intention is legitimate because bio-logical research has not yet resolved such controversialissues as pattern formation or the relationship betweenontogeny and phylogeny, just to mention the most in-teresting ones. As a methodical cue, Mocek uses Kuhn’sparadigm that is narrowed down to the postulate thatnature behaves in a rational way such that we cancomprehend nature’s phenomena. To put it anotherway, the naturalists and scientists explain causally allphenomena that are observed in nature on the basis ofunderlying regularities, or even natural laws (p. 24).Whether this paradigmatic approach was well or effec-tively chosen is a decision that will be left to the reader.The author implicitly argues more with pragmatic clus-ter terms when he furnishes his inquiry with concep-tual opposites such as vitalism versus mechanicism,epigenesis versus preformation, or a conception of mor-phogenesis either controlled by the nucleus or inducedby the protoplasm.

After a short introduction (pp. 17–41), the first partdiscusses the sophisticated advances of natural phi-losophers and scientists such as Kant, Wolff, Schelling,Haeckel, Gegenbaur, and others who influenced the ad-vancement of causal morphology. The interesting thingconcerning the first part is the author’s argumentabout the Kantian impact on a philosophy of biology.According to Mocek, one should see Kant more as aphilosopher of science than an idealistic natural phi-losopher and transcendental thinker (p. 55f). The sec-ond part concretizes in three very detailed case studiesof His (pp. 103–181), Roux (pp. 183–255), and Driesch(pp. 257–332) the factual history of causal morphologyhidden inside molecular genetics. The third and lastpart (pp. 333–407) contains, a little too compressed,descriptions of possible connections to recent advancesin morphogenesis and developmental genetics. The an-notations (pp. 408–453) are very informative and referto relevant research. However, the reader can not avoidthe impression that Anglo-American research on thissubject is not treated properly, i.e., it is actually notincorporated. The literature (pp. 454–515) is extremelyextensive and contains many works, written in Ger-

American Journal of Medical Genetics 87:281–285 (1999)

© 1999 Wiley-Liss, Inc.

man, which are often overlooked by historians of biol-ogy. The complete bibliographies of His, Roux, andDriesch follow and will become an indispensable re-source for further biohistorical research.

How does Mocek understand causal morphology?What does it really mean? For him, it encompasses ascientific discipline that analyses self-organizing sys-tems with experimental methods. These systems wereapproached by His, Roux, and Driesch with descriptiveconcepts, which corresponded to the causal-mechanicalthought patterns of their times. It was not until thefirst decades of the 20th century, after further experi-mental research in developmental biology, that a newsystem-theoretical context of instruction was formu-lated beginning with the organismic synthesis of Lud-wig von Bertalanffy (1901–1972). Causal morphology ishere viewed as a transitional link between the moredescriptive research methodology of earlier times andthe experimental analyses of our times. As the firstexperimental discipline of biology, causal morphologyinitiated the conversion of naturalistic biology (Natur-geschichte) to natural science (Naturwissenschaft).This was achieved by transforming the more or lessstatic form concept of classical morphology to a dy-namic one of pattern formation whereby physiology,which was acknowledged as the most physical branchof biology, was of great help. This may impress as para-doxical, particularly when one considers that His andRoux, both trained anatomists, transferred the prin-ciples of classical mechanics, as used in their anatomi-cal discipline, to embryology. To von Baer’s epigeneticinterpretation of ontogeny, anatomic mechanics wasadded involving pressures and tensile forces, whichbased the fruitful “either/or” of causal morphology (En-twicklungsmechanik), on classical morphology and themodern physiology of morphological research. This be-gan the triumphant march of physiology into the ana-tomic-morphological domain. According to Mocek, thevarious positions of developmental physiology and ana-tomical morphology communicated with each other be-cause both included self-organizing approaches. Thesecond part of this monograph attempts to verify thatcentral hypothesis.

In 1872 the Swiss anatomist Wilhelm His was ap-pointed Director of the Institute for Anatomy inLeipzig, at the suggestion of Carl Ludwig (1816–1895).He based his physiological theory of morphogenesis onBaer’s quest for a law of growth [His, 1868]. The shap-ing mechanics (Bildungsmechanik) His compared tothe deformability of an elastic plate being stretchedunevenly. For the author, this describes the first at-tempt in the history of biology to explain the self-shaping of organic form and the growth movements ofthe embryo under the developmental conditions of ananatomical mechanics (p. 109). Besides Karl Ernst vonBaer, the physician and natural philosopher RudolfHermann Lotze (1817–1881), who incorporated physi-ological perspectives into biomedicine in general, had adeep and long-lasting impact on His. Consequently,also for Roux’s causal-morphological program of En-twickelungsmechanik (for the correct spelling see p.408), Lotze’s basic idea that an organism is a (purpo-sive) combination of mechanical processes became one

of the most important impulses. This is the main rea-son why His, neglected by historians of biology untilrecently, is portrayed as the mentor or preceptor ofexperimental embryology. The author summarizes His’theory of morphogenesis in a single sentence, whichHis elaborated, corrected, and specified during hiswhole life: “morphogenesis is the shaping of embryonicparts triggered by the growth of the embryo” (p. 120).In the following, Mocek analyzes the main statementsas, for instance, the importance of cell theory, thephysiological results of the theory of germ layers, therelationship between preformation and epigenesis, be-tween heredity and mechanical patterning, and illus-trates them on the basis of His’ work on chick develop-ment. Contrary to Roux who based his theoretical re-flections on intuition well founded on experience, Hisstarted with an idea, namely, the conception of the ger-minal disc as an elastic plate (q.v., his tests with sheetsof paper and leather).

Because of his geometrical hypotheses, His’ principleof the organogenic areas of the embryos was that theanlage of the upper limb is situated near the head, thenin the region of the neck and, finally, the proximal lat-eral part of the thorax. In other organs, e.g., the med-ullary tube, the morphogenetic topography, and the an-lage coincide. His construed this phenomenon with aspecific folding geometry by which a localized mecha-nism triggers the ontogenetic form (p. 134). Becausemorphogenesis, and therefore folding, was derivedfrom growth, His explained the folding geometry bymeans of an analysis of growth phenomena [His, 1874,p 153]: “. . . daß auch die Wachsthumserregung [desEies] eine Function von Raumund Zeit ist.” [Thegrowth potential of the embryo has to be a function ofspace and time.]

According to Mocek, this statement anticipates theharmonious-equipotential system of Driesch because ithas reference to the spatial components of positionalrelations in the embryo. The capability of the sperm toimpart growth potential to the ovum during fertiliza-tion, His [1868] conceptualized as formative irritability[cf., Loeb, 1908; Herbst, 1901, 1908]. Interesting in thiscontext is that His, whom Mocek rightly describes asan epigenetic physiologist (p. 147), did not substantiatethe hypothesis of a heterozygous cleavage of embryoniccells genetically, but used physiology and histogenesis,incidentally, in the sense of his medical training. Nowthe ontogenetic history of every single form could beformulated as an issue of mechanics, in fact either as anumerical abstraction or as a physico-chemical func-tion of space-time (p. 159). The author’s comment onthe morphogenetic field theory, as developed by Alex-ander Gurwitsch (1874–1954) and Paul Weis (1898–1989) is correct, at least from a formal point of view.However, the author does not consider that both reliedon other precursors as, for instance, August Rauber(1841–1917), an assistant of His, Hans Driesch, andHans Spemann (1869–1941). Furthermore, both usedother experimental systems; Gurwitsch derived hisfield trajectories from the camomile blossom and fungi,and Weiss measured the outgrowth of the field-matrixin tissue cultures.

The second chapter deals with Wilhelm Roux who

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directed the Institute for Anatomy in Halle from 1896until his retirement, and his Entwickelungsmechanik.To succeed with his conception of causal morphology,Roux founded the very influential journal Archiv furdie Entwickelungsmechanik der Organismen (pres-ently referred to as Development, Genes, and Evolu-tion) at the end of 1894 and edited the following 59volumes [cf., Counce, 1994; Sander, 1991, 1997]. Nodoubt, Roux was one of the first biologists who compre-hended morphogenesis as a dynamic complementationof hereditary and ontogenetic lawfulness (p. 194). Sincein Roux’ approach the internal components of an or-ganism were always the decisive ones, developmentrepresented a unity of nuclear potential and morpho-genesis. His scientific ideal for biology was the physicalsciences; consequently, he experimentally investigated,in continuation of Pfluger’s trials, a supposed directiveimpact of gravitation on the developing embryo[Pflüger, 1983]. From experiments with frogs, Roux de-rived rules by which the directive determination of theembryo was fixed. These differentiation rules stronglyinfluenced the terminology of developmental biology,e.g., cleavage as self-differentiation of embryonic parts,or embryonic development as a mosaic activity. Owingto his experimental methods, Roux could “prove” thephysiological principle of ontogenetic formation, some-thing that distinguished him strongly from his contem-poraries. He was even able to describe how structurescould unfold in correspondence to a mechanical tensionof pressures and tensile forces. Roux thought a differ-ent, trophic stimulation was decisive, which he para-phrased in a metaphorical and programmatic way asthe fight of the parts of the organism [Roux, 1881,1895]. In fact, such a behavior stressed the concept offunctional adaptation, a kind of internal adaptation ofthe organism. In Mocek’s interpretation, it is charac-terized as a system that emerges out of inherent struc-tures linking genetic variability and selectivity. Thus,this principle describes a self-organizing activity of theliving organism (p. 227f). Mocek does not include in hismonograph a discussion of botany, because botanicalarguments had no relevant impact on developmentalphysiology (p. 448f). However, in this particular caseone misses a note on the concept of the functional ex-ploitation of the botanist Karl Goebel (1855–1932), oneof the founding fathers of experimental embryology, bywhich internal patterning laws can be used to predictresponses to specific environmental functions [Goebel,1898].

In Roux’ conception the self-regulation of the organ-ism was determined as a basic property of life, wherebyhe distinguished between typical and atypical (regula-tory) development. He formulated this system charac-ter of life as follows [Roux, 1893, p 432]: “Organismensind [...] fast vollkommen in sich selber geschlosseneKomplexe außerst vielfacher innerer Wechselwirkun-gen, fur welche von außen her nur die Vorbedingungengeliefert werden mussen; wahrend die besondereQualitat aller normalen und selbst der pathologischenWirkungen im Organismus selber bestimmt wird.” [Or-ganisms are (...) almost completely closed complexes ofnumerous internal interactions for which the environ-ment supplies only support while the special quality of

all normal and even pathological outcomes is deter-mined by the organism itself.]. Mocek assumes fromRoux’ works until the end of the 1890s that the newtheoretical horizon was explicitly based on the experi-mental method. Therefore, he concludes, Roux de-serves the merit of having founded experimental biol-ogy (p. 208f) the genetic research program of whichshould concentrate on the activities of the nucleus andnot to the structure of the nucleus. Because it is a ques-tionable conclusion to name Roux the founder of experi-mental biology, it would have been more reasonable tolimit his undisputed merits to experimental morphol-ogy. Whereas His understood in a descriptive way theshaping of the embryo more or less as a static folding,Roux carried out the final step towards the develop-mental physiology of self-organizing organisms; the au-thor speaks of a first synthesis of developmental biol-ogy (p. 229). Summing up, Mocek states that Rouxshowed the first approach to combining developmentalbiology and genetics. The author corroborates it by theconjecture that self-regulation is the triggering mecha-nism by which the genetic information is translatedinto ontogenetic processes, whereby the former is si-multaneously regulated by the translocation (p. 253).To put it another way, Mocek thinks of Roux as thepredecessor of molecular feedback circuits and regula-tory networks. Whether this judgement of Roux’sachievements is correct, or whether Roux is definitelyoverestimated, will not be pursued here because it de-serves much further research.

The last chapter of the second part discusses HansDriesch and his system-theoretical concept of causal-ity. Driesch, who lectured as a professor of natural phi-losophy at the University of Leipzig from 1923, startedhis eventful career as a student of Ernst Haeckel(1834–1919). With the famous sea urchin experimentshe demonstrated his talent for developmental biology.Limiting the study to 1899 allows Mocek to shade outthe (metaphysical) concept of entelechy as it was for-mulated by the later Driesch. Hence, until 1899, Dri-esch [Driesch, 1899, p. 99] interpreted neovitalism stillvery cautiously: “als diejenige Auffassung, welche inLebensgeschehnissen Vorgange mit der ihnen eigen-thumlichen Elementargesetzlichkeit erblickt” [as theview which characterizes living phenomena as eventsof a specific lawfulness]. Therefore, the Gifford Lec-tures The Science and the Philosophy of the Organism,held at the University of St. Andrews in 1907, unfor-tunately are not included in the critical review. Inthese lectures Driesch explained organismic develop-ment on the basis of the “harmonious-equipotental sys-tem” [Driesch, 1908, p. 90] and the molecular “suspen-sion theory” [Driesch, 1908, p, 472] approximatinglater self-organization theories of genetic evolution.

Two works of Driesch completed before 1899, whichMocek considers very important and highly influential,are the thesis written under Haeckel in 1889 and thetreatise Die mathematisch-mechanische Betrachtungmorphologischer Probleme der Biologie [1891], whichaccording to Driesch’ self-assessment, introduced allthe later works. At the end of 1890 Driesch publishedthe theoretical essence of his experiments on the tec-tonics of hydropolyps in which the growth law was de-

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termined physiologically as the bifurcation of a devel-opmental trajectory (p. 282). To illustrate this nowa-days one could refer, for instance, to the movingboundary problem. The most momentous conceptswere, apart from entelechy, prospective meaning andprospective potency. The former characterizes the mor-phogenetic law as an inherent property of the organismunder study; the latter describes, from an embryonicpoint of view, how an ordered structure can re-establish itself after disturbances (self-regulation).Both are activities of the embryo, which was defined byDriesch as a harmonious-equipotential system inwhich the reaction chains proceed inside specific em-bryonic regions and cells in a branching manner. Thebasis of this terminology was an experiment in 1894/1895 on gastrulating embryos of Sphaerechinus granu-laris which Mocek designates as an experimentum cru-cis for morphogenetic theory of Driesch (p. 315).

Over the next years, Driesch changed his perspectivefrom a causal to a teleological one, a shift that Moceksees as a venture towards a systemic alternative ofdescription. By means of this very perspective Rouxand Driesch differ essentially from each other, even ifthey shared a similar sympathetic attitude towardsmechanicism on which all scientific research has torely. Mocek interprets the neovitalism elaborated byDriesch from 1895 until 1899, as a system-theoreticalvariant and Driesch himself as one of the first theore-ticians of modern self-organization theories (p. 308ff).For Mocek, Driesch had to recognize that his experi-mental data were not compatible with the Weisman-nian theory, which was restricted to nuclear activities.Therefore, he searched for new evidence of the epige-netic process of embryonic development in which thegenetic information is effected during ontogeny. How-ever, Driesch chooses the wrong word for it, namely,entelechy, and not the self-organizing paradigm as thecharacteristics of an epigenetic germ theory. The rea-son for it is obvious; the modern word self-organizationdid not exist yet. Mocek’s arguments that are con-strued, among others, by the wholistic causality (Ganz-heitskausalitat) amount to the assumption that, exceptfor the concept of entelechy, Driesch’s neovitalism fi-nally represents a mechanicism transferred to a sys-tem-theoretical approach (p. 321). That may be: how-ever, it will take some time until the history of biologycan fully appreciate that interpretation. As original asMocek’s statement may sound, it is not really new. Ber-talanffy already named Driesch from the end of the1920s a mechanistic and reductionistic vitalist forwhom development took part in completely isolatedparallel sequences without allowing interactions be-tween the particular developmental stages [Bertalan-ffy, 1930, 1931; q.v. also Driesch, 1891a,b].

The third and last part is devoted, in a rathersketchy way, to connect these conceptions to the mostrecent ones focusing on evolution and marked by theholistic break around the turn of the century. First, thesuccessors including Theodor Boveri, Oscar Hertwig,Edmund Beecher Wilson, among others, are discussedbriefly. Wilson and, therefore, the American variant ofdevelopmental biology differed essentially from its Ger-man counterpart because of its starting point from cell

biology, which finally meant a long overdue break-through for it. With the help of cell morphology thisstarting point postulated that the problem of heredityand development would be solved in the future. Thus,cell biology could combine these disparate domains un-der a single point of view. Now, genetic hypothesescould be controlled by developmental experiments,and, conversely, those experiments could be inter-preted by genetics (p. 334f). For the first three decadesof the 20th century Mocek names the gradient theory ofCharles M. Child (1869–1954), the morphogenetic fieldof Gurwitsch and Weiss, and the organizer of Spe-mann. However, because they could not really solve theissue of emerging form, research on embryonic devel-opment shifted during the 1940s constantly fromphysiology to biochemistry to molecular genetics. Onereason was, of course, that one used other experimentalsystems because of a refinement of experimental meth-ods — a fact the author does not discuss. French de-velopmental biology, with its emphasis on teratology, isdiscussed briefly; and the importance of Roux’s andDriesch’s conception for most recent approaches on ge-netic morphogenesis is pointed out. To sum up approxi-mately, for all three (biomedical) scientists, the embryowas a system that creates ordered structures wherebythe traditional static perspective on morphogenesis be-came dynamic, comparable to modern self-organiz-ing theories. Because all three theories shared the con-viction that the wholistic structure represents a shap-ing, conditioned by function, Roux and Driesch couldhave relied on His, at least from a chronological point ofview. The recognition that the emerging form becamethe pivot of morphophysiology is because of His, asMocek states. However, as far as I can judge, neitherDriesch nor Roux referred explicitly to His who appar-ently did not influence their conceptions.

Mocek’s monograph is recommended because it cor-rects several misinterpretations, partly because of in-correct translations, and because it offers new informa-tion about these three founding fathers of experimentalembryology, e.g., the political liberalism of Driesch,just to mention two important reasons. It will not sur-prise that it contains some minor errors. For instance,Weiss based his theoretical approach on the machinemetaphor; and there existed a developmental biology inEngland [cf., Needham, 1936; Waddington, 1940].Moreover, one misses a concise discussion of the rela-tionship between developmental biology and develop-mental genetics, or a comment on Needham’s classics,which elaborated in an admirably elegant stylistics thestate of developmental biology in those times, or a re-mark about the monograph by Webster and Goodwin[1996], which aimed towards a new theory of biologicalforms (whether new, cannot be pursued here). How-ever, these remarks are minor details. More serious isthe over-strained paradigm of evolutionary self-organi-zation to which the author fits nearly all concepts ofclassical developmental biology, particularly becausethis paradigm is based on physical theories simulatednowadays by the computer, not on experiments withliving organisms. Thus, the author, in effect, some-times negates the specificity of developmental biology.

Nevertheless, the book is recommended to all histo-

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rians and philosophers of biology and to biomedical sci-entists who are researching pattern formation, emerg-ing form, and who are, in general, interested in thehistory of biology. Hopefully, no potential reader will bedeterred by the gushing style, the superlatives, and theexclamation marks scattered over the text in an infla-tionary manner. In view because of the last point, themonograph should be re-issued in a condensed Englishversion as soon as possible and be complemented by asubject index that the German edition omitted.

ACKNOWLEDGMENTS

I thank Lynn K. Nyhart and Nick Hopwood for anexchange about the crucial topic of the history of causalmorphology during the Oaxaca Meeting of theISHPSSB. My special thanks, however, belong to JohnM. Opitz for numerous discussions and the final cor-rections. Supported in part by a grant from the Pri-mary Children’s Medical Center Foundation in supportof the International Clinical Genetics Research andConsultation Program, Division of Medical Genetics,Department of Pediatrics, University of Utah.

REFERENCESBertalanffy L von. 1930. Lebenswissenschaft und Bildung. Erfurt: Kurt

Stenger.

Bertalanffy L von. 1931. Tatsachen und Theorien der Formbildung als Wegzum Lebensproblem. Erkenntnis 1:361–407.

Churchill FB. 1973. Chabry, Roux, and the experimental method in nine-teenth-century embryology. In: Giere RN, Westfall RW, editors. Foun-dations of the scientific method: the nineteenth-century. Bloomington:Indiana University Press. p 161–205.

Counce SJ. 1994. Archives for developmental mechanics. W. Roux, Editor1894–1924. Roux Arch Dev Biol 204:79–92.

Driesch H. 1891a. Die mathematisch-mechanische Betrachtung morpholo-gischer Probleme in der Biologie, Eine kritische Studie. Jena: G.Fischer.

Driesch H. 1891b. Die Stockbildung bei den Hydroidpolypen und ihre theo-retische Bedeutung. Jenaische Zeitung fur Naturwissenschaft 25, NF.18:467–479.

Driesch H. 1899. Die Lokalisation morphogenetischer Vorgange. Ein Be-weis vitalistischen Geschehens. Archiv fur Entwick(e)lungsmechanikder Organismen 8:35–111.

Driesch H. 1908/1921. Philosophie des Organischen (Gifford Lectures). 2ndedition. Leipzig: W. Engelmann.

Gilbert SF, editor. 1991. A conceptual history of modern embryology. NewYork: Plenum.

Gilbert SF, Opitz JM, Raff RA. 1996. Resynthesizing evolutionary anddevelopmental biology. Dev Biol 173:357–372.

Goebel K. 1898. Uber Studium und Auffassung der Anpassungsers-cheinungen bei Pflanzen. Munchen: Verlag der Akademie.

Hamburger V. 1988. The heritage of experimental embryology. Hans Spe-mann and the organizer. Oxford: Oxford University Press.

Herbst C. 1901. Formative Reize in der tierischen Organisation. Leipzig:W. Engelmann.

Herbst C. 1908. Besprechung von J. Loeb, Uber den chemischen Charakterdes Befruchtungsvorganges. Archiv fur Entwick(e)lungsmechanik derOrganismen 25:569.

His W. 1868. Untersuchungen uber die erste Anlage des Wirbelthierleibes.Die erste Entwickelung des Huhnchens im Ei. Leipzig: F. C. W. Vogel.

His W. 1874. Unserer Korperform und das physiologische Problem ihrerEntstehung. Briefe an einen befreundeten Naturforscher. Leipzig: F. C.W. Vogel.

Lenoir T. 1982. The strategy of life. Teleology and mechanics in nine-teenth-century German biology. Dordrecht: Reidel

Loeb J. 1908. Uber den chemischen Charakter des Befruchtungsvorgangsund seine Bedeutung fur die Theorie der Lebenserscheinungen. In:Vortrage und Aufsatze uber Entwick(e)lungsmechanik der Organis-men 2. Leipzig.

Maienschein J. 1991. The origins of Entwicklungsmechanik. In: GilbertSF, editor. A conceptual history of modern development. New York:Plenum. p 43–61.

Needham J. 1936/1968. Order and life. Cambridge, MA: M.I.T. Press.

Nyhart LK. 1987. The disciplinary breakdown of German morphology,1870–1900. Isis 78:365–389.

Nyhart LK. 1995. Biology takes form: animal morphology and the Germanuniversities, 1800–1900. Chicago: Chicago University Press.

Oppenheimer JM. 1967. Essays in the history and embryology of biology.Cambridge: M.I.T. Press.

Oppenheimer J. 1970. Cells and organizers. Am Zool 10:75–88.

Pfluger A. 1883. Ueber den Einfluss der Schwerkraft auf die Theilung derZellen und die Entwicklung des Embryos. Pfluger’s Archiv 32:1–79.

Roux W. 1881. Der Kampf der Teile im Organismus. Biologisches Centr-alblatt 1:241–251.

Roux W. 1893. Entwickelungsmechanik, Anatomische Hefte, 2. Abt.:Ergebnisse der Anatomie und Entwickelungsgeschichte 2(1892):415–445 (In: Gesammelte Abhandlungen uber Entwickelungsmechanik derOrganismen. Bd. 2. Leipzig: W. Engelmann. p 55–94.)

Roux W. 1895. Der zuchtende Kampf der Theile oder die Theilauslese imOrganismus (eine Theorie der funktionellen Anpassung). Ein Beitragzur Vervollstandigung der Lehre von der mechanischen Entstehungdes sogenannten Zweckmassigen. Mit einem Vorwort zum zweiten Ab-druck. In: Gesammelte Abhandlungen uber Entwickelungsmechanikder Organismen. Bd. 1. Leipzig: W. Engelmann. p 139–422.

Sander K. 1991. Landmarks in developmental biology. Roux Arch Dev Biol200–203.

Sander K, editor. 1997. Landmarks in developmental biology, 1883–1924.Heidelberg-Berlin: Springer.

Waddington CH. 1940. Organisers and Genes. Cambridge: Cambridge Uni-versity Press.

Webster G, Goodwin BC. 1996. Form and transformation: generative andrelational principles in biology. Cambridge: Cambridge UniversityPress.

Sabine BrauckmannDepartment of PediatricsUniversity of UtahSalt Lake City, Utah

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