Amoebae as Exemplary Cells: The Protean Nature of an Elementary Organism

Amoebae as Exemplary Cells: The Protean Nature

of an Elementary Organism

ANDREW REYNOLDSDepartment of Philosophy & Religious StudiesCape Breton University1250 Grand Lake Road

P.O. Box 5300, Sydney, Nova ScotiaCanada B1P 6L2E-mail: [email protected]

Abstract. In the nineteenth century protozoology and early cell biology intersectedthrough the nexus of Darwin’s theory of evolution. As single-celled organisms, amoebaeoffered an attractive focus of study for researchers seeking evolutionary relationshipsbetween the cells of humans and other animals, and their primitive appearance made

them a favourite model for the ancient ancestor of all living things. Their resemblance tohuman and other metazoan cells made them popular objects of study among mor-phologists, physiologists, and even those investigating animal behaviour. The amoeba

became the exemplar of the new protoplasmic cell concept of mid-century and becauseits apparent simplicity made it widely generalizable it became a popular subject in abreadth of experimental investigations and theoretical speculations. It was able to do

this because ‘‘the amoeba’’ denotes not a particular organism, but a general type ofbehaviour common to the cells of a range of protozoa, simple plants and higher animals.Its status as an exemplary cell also rested upon auxiliary philosophical assumptions

about what constitutes a primitive characteristic and the thesis that evolution is aprogressive development of order from chaos.

Keywords: Amoebae, cell theory, evolution, exemplary materials, protoplasm, WilliamBenjamin Carpenter, Michael Foster, Ernst Haeckel, T. H. Huxley

‘‘Together with echinoderm eggs, amoebae have been among themost important cells used to elucidate the properties of proto-plasm.’’ I. Joan Lorch, 1973, p. 30

‘‘The higher animals, we learn from morphological studies, may beregarded as groups of amoebae peculiarly associated together.’’Michael Foster, 1880, p. 4

Journal of the History of Biology (2008) 41:307–337 � Springer 2007

DOI 10.1007/s10739-007-9142-8

Introduction

From its introduction in the mid-eighteenth century to its developmentin the nineteenth century into one of the most important generaltheories of biology, the concept of the cell has undergone significantmodifications. An important factor in these changes has been thedifferent organic materials which competing investigators took to beexemplary of the cell concept.1 The original notion of the cell as beingakin to a little room with a rigid wall was the result of RobertHooke’s (1635–1703) investigations of dead cork under the microscope(Hooke 1665). Matthias Schleiden (1804–1881) extended this cellconcept to plants generally by emphasizing the presence of distinctwalled units in the structure of plant tissue. Theodore Schwann (1810–1882), by focusing on the cellularized structure of developing cartilagein animal embryos was thereby able to extend the cell concept toanimals and to offer a truly general theory of living organisms. Asother researchers focussed their microscopes on materials such as frogeggs in the process of division and on muscle tissue, the idea of the cellunderwent significant changes, resulting most notably in Max Schu-ltze’s (1825–1874) insistence in the 1860s that the existence of anenveloping wall or membrane was a nonessential feature. Schultzebased his conclusions on his own comparative studies of the sarcodeor protoplasmic material of animal muscle tissue and of rhizopodprotozoans, and on the botanist Anton de Bary’s (1831–1888) study ofslime mould amoebae.2 In such organic material there is little sign of arigid wall or distinct membrane characteristic of the original cellconcept. Schultze reformed the cell theory by redefining the cell as a‘‘naked speck of protoplasm with a nucleus’’.3 With the advent of thisprotoplasmic version of the cell theory, the concept of the cell becameintimately tied to one form of rhizopod organism in particular, theamoeba.4

1 Mendelsohn, 2003.2 De Bary, 1859. Rhizopod (literally ‘root-foot’) refers to the slender pointed pseu-

dopodial processes extended by some single-celled organisms. These can originate eitherfrom a protoplasmic mass situated within a shell or test (e.g. foraminfera) or from a

naked (test-less) amoeba. Pseudopods of the latter tend to be blunter and shorter inlength.

3 See Schultze (1861, 1863).4 I will follow the standard convention of writing ‘‘amoeba’’ to refer to any amoeba-

like organism from a number of distinct genera and Amoeba for the particular genus of

that name.

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The amoeba became a common symbol of the cell, and an exemplarymaterial for many biological studies, because of its unique properties. Itis simple in structure (compared to many other animals, plants, andprotozoa); it was commonly assumed to be the most primitive form ofcell known; it is similar in appearance (depending upon the life-cyclestage at which it is observed) to the eggs or embryonal cells from whichmany animals develop, as well as to cells in what was commonlybelieved to be the most complicated or highly evolved organism, thehuman body. In addition to these more theoretical features, it has theadded practical advantages of being easy to find and to maintain in alaboratory setting.

The combination of the protoplasmic theory of the cell with thetheory of evolution also gave the amoeba special importance. Its pro-tean nature – its ability to assume different forms and to exhibit all thefundamental properties of life – allowed it to play a variety of roles in anumber of different biological questions, serving at once as an ‘‘ele-mentary organism’’ and as an analogue (or even homologue accordingto some evolutionary interpretations) to cells in the complex humanorganism. The amoeba represented a morphological type or form of life,but as Andrew Mendelsohn has argued is true of exemplary materials, itwas also exemplary of a general theory about the nature of life itself.5 Itwas able to do this, I argue, because ‘‘the amoeba’’ actually denotes nota particular, but a type. Throughout the nineteenth century the term‘‘amoeba’’ (and cognates like ‘‘amoeboid’’ and ‘‘amoebiform’’) wereused to refer not to a particular organism (or particular species oforganism), but to a general morphological form and mode of behaviour.This allowed the amoeba, or rather amoebae and amoeboid cells, to bewidely generalizable across a variety of theoretical contexts andempirical investigations.6 While it would be too much to maintain thatthere was universal agreement among biologists about taking amoeba asexemplary of the cell concept and the protoplasmic theory of life, thereis ample evidence showing it to have been a generally acceptedassumption, which even when not explicitly stated, often workedimplicitly to guide biologists’ understanding of the nature of organismsand cells.

5 Mendelsohn, 2003, p. 34.6 Mendelsohn, 2003, p. 16 writes of exemplary materials that ‘‘the particular is

exemplary, in a strong sense of the word. It becomes the general. The thing becomes thetheory, as it were, becomes the identity of the general object cell’’. The point I ammaking is that it was particularly easy for the amoeba to become the general since talk

of ‘‘the amoeba’’ already refers to a general concept or type.

AMOEBAE AS EXEMPLARY CELLS 309

Discovery and Classification of Amoeba

Today when someone talks of an amoeba they typically mean a nakedor shell-less, free-living organism of the genus Amoeba, for instanceAmoeba proteus.7 The first amoeba was observed, oddly enough giventheir ubiquity, not by the discoverer of the microbiotic world, Antonyvan Leeuwenhoek (1632–1723), but by Rosel von Rosenhof (1705–1759), who in 1755 named the organism he observed the ‘‘little Proteus’’(der kleine Protheus) due to its ever changing form (Figure 1). Linneaus(1707–1778) later changed its scientific name to Volvox chaos (1760) andthen later to Chaos protheus (1767). The Danish naturalist Otto Muller(1730–1784) called it Proteus diffluens (1786). It was ChristianEhrenberg (1795–1876) who first introduced the now standard taxo-nomic term Amoeba in 1831, from the Greek ‘‘amoibos’’ for changing,though Bory de St. Vincent (1778–1846) had used the variant spellingAmiba in 1824.8 The characteristic feature of amoebae is their move-ment by the extension of non-permanent pseudopodia from any part ofthe body surface. In this way they are true shape-shifters and it was forthis reason that Rosenhof called the specimen he observed the littleProteus, after the shape-shifting god of Greek mythology. Ehrenbergtook the existence of contractile and water vacuoles for little stomachsand so classified them as polygastria, and conceived the amoebae to be,along with the other infusoria, ‘‘perfect’’ (volkommene) or completeanimals.9 Others rejected this interpretation and considered them to berepresentatives of a much more primitive construction. Albert Kolliker(1817–1905) and Carl von Siebold (1804–1885) argued that they con-sisted of but a single cell, and Ernst Haeckel (1834–1919) grouped at

Kingdom Protozoa

Phylum Protozoa

Subphylum Sarcodina

Superclass Rhizopoda

Class Lobosa

Order Amoebida

Family Amoebidae

Genus Amoeba

Ehrenberg

Species Amoeba proteus

7 Classification of the amoebae is notoriously difficult and in constant flux, but a

common taxonomy, from the Integrated Taxonomic Information System (http://www.itis.gov) is as follows:

8 See Leidy (1879) and Lorch (1973) for histories of the various classifications.9 Ehrenberg, 1838.

ANDREW REYNOLDS310

least some types in which he could see no nucleus within his kingdom ofMonera, the unicellular ‘‘organisms without organs’’.10 There is littlequestion that they give the appearance of being very primitive as theyare lacking in any permanent differentiated parts other than a nucleus.11

This absence of any permanent shape or differentiated structure evokedbeliefs about the primitiveness of that which is without form; hence theearly taxonomic name Chaos. Amoebae are presently considered apolyphyletic group, and ‘‘amoeba’’ is more a descriptive term for a habitof movement and feeding by pseudopod formation and protoplasmic

Figure 1. Redrawings from Rosel von Rosenhof (1755) of the little Proteus. FromJeon 1973, p. 4. Reprinted with permission from Elsevier.

10 Kolliker 1845; Siebold, 1849; Haeckel, 1866.11 Those Haeckel had claimed to be lacking a nucleus, his Protamoeba for instance,

were eventually found to possess this feature by later observers.


streaming applicable to a wide range of cells across several major taxa.12

But it is for this very reason that they could serve as an exemplar of thecell concept in general.

Nineteenth-Century Theories of the Unity of Life and the Type Concept

In light of their apparently primitive nature one would be excused forthinking that no two things could be more different, more distant fromone another, than a human being and a lowly amoeba. Yet according tothat synthetic vision of the organic world expressed by the phrase ‘‘frommonad to man’’, the two were thought by many to be but separate endsof a continuous ‘‘chain of being’’. But more than this, from the unifyingperspective afforded by the nineteenth century theories of evolution andcell theory, human beings, in so far as they were conceived as multi-cellular organisms, could be viewed as ‘‘colonies of amoeba-likeorganisms’’, the amoeba-like organisms being the cells themselves.13 Infact, one of the most influential physiologists of the latter half of thenineteenth century, England’s Sir Michael Foster (1836–1907), waswilling to drop the qualifying ‘‘-like’’ in that phrase: he regarded hu-mans and other animals as ‘‘groups of amoebae peculiarly associatedtogether’’.14 How was it that such an extraordinary-sounding claimbecame respectable enough to be endorsed by one of the leading labo-ratory biologists of the day? The answer takes us deep into the theo-retical assumptions of the life sciences in the nineteenth century.

Stephen Jacyna has explained how the romantic conception of life,with its belief in the unity of organization and function in the organicworld, rendered early-nineteenth century British life scientists wellprepared for acceptance of the cell theory as advocated by the GermansMatthias Schleiden (1804–1881) and Theodore Schwann (1810–1882).15

Jacyna quotes the physiologist Thomas Southwood Smith (1788–1861),who wrote in 1827: ‘‘whatever is once ascertained to be true relative tothe elementary organization and action of a living being of anydescription, will ultimately be discovered to be true of all...’’16 With its

12 Margulis et al., 1990, pp. 8, 15.13 The comparison between the plant or animal body composed of many cells and a

society or state composed of many citizens was a popular one in the nineteenth century.See Weindling (1981), Sapp (2003), especially ch. 8, Reynolds (2007).14 Foster, 1880, p. 4.15 Jacyna, 1984.16 Ibid., pp. 21–22.

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emphasis on the unity of form and function the romantic programmeprepared researchers to identify the essential properties of life in thesimplest instance and to extend it up the scale of organic beings.Richard Owen (1804–92) noted analogies between the lowest infusoriaand human cells as early as 1843, but of ciliates primarily, not rhizopodor amoeboid forms.17 In 1844 Thomas Wharton Jones (1808–1891) gavethe first published description of the similarities between the amoebaeand the white blood corpuscles.18 Jacyna notes that the romantic con-ception incorporated a belief in a parallel between the micro- andmacro-cosms; ‘‘[T]he discovery of the type of a given structure orfunction – conceived as an elemental manifestation of that phenomenonwhich gave access to its universal biological character – was seen as acentral goal’’.19 Many leading life scientists of the nineteenth century(anatomists, embryologists and others) believed that in the cell they hadfound such a type.

The type concept was actually a complex of related notions used bybiologists rather differently in different specialties and at different levelsof organization.20 The morphological-type concept was integral to thepractitioners of comparative anatomy throughout the nineteenth cen-tury. A morphological type need not be a transcendental archetype, norwere those who employed the concept necessarily committed to belief inthe fixity of species or special creation. For those who fashioned the celltheory, the concept of a morphological type was crucial; and thisremained true for the architects of the reformed protoplasmic cellconcept to be discussed below. But whereas the original cell theorysought to unify the phenomena of life through a common morpholog-ical type, the protoplasm theory initially attempted to achieve thisthrough identification of a common substance or material. The amoebaquickly became exemplary of the protoplasm theory and provided abridge between the traditional cell concept (in terms of a morphologicaltype) and the newer protoplasmic concept (in terms of an essentiallyamorphous substance). The revised cell concept, now commonlyexemplified by and identified with the lowly amoeba, also worked wellin the context of evolutionary theories about the community of descentand the rise of complex, orderly creatures from simpler, more primitiveones.

17 See Owen (1855), especially pp. 39–42, 643–648.18 Jones, 1844.19 Jacyna, 1984, p. 41.20 Farber, 1976.


The Protoplasm Theory

The idea of the cell as formulated by Schleiden and Schwann with itsinsistence upon a rigid wall or enclosing membrane became increasinglyunattractive to those who were investigating the lower animals of theprotozoan variety. Although others had begun insisting on the non-essentialness of a cell wall before him, it was the anatomist MaxSchultze who argued most forcefully for a new conception of the cellthat emphasized the protoplasmic contents rather than an envelopingwall or membrane.21 In making the case that the essential type of the cellwas, as he defined it, ‘‘a naked clump of protoplasm with nucleus’’,Schultze drew on his investigations of rhizopods to show the essentialsimilarities between these simple protozoan organisms and the ana-tomical elements of higher animals, such as the Muskelkorperchen or‘‘small masses of protoplasm containing nuclei that occur among oroutside the contractile elements of striated muscle’’.22 In the 1861 paper,‘‘On muscle-bodies and what one should call a cell’’, Schultze asked,‘‘What is the most important criterion of a cell?’’ Noting that cells comein such diverse forms he rephrased the question as ‘‘Which are the mostimportant [wichtigsten] cells?’’ To this question he replied, those cells inwhich lies the greatest potential for the formation of all the varioustissues of the living body. These are the egg cells or ova (Eizellen), for inthem ‘‘rests the future of the entire organism’’.23 Such cells he says canbe characterized as ‘‘membraneless clumps of protoplasm with a nu-cleus’’.24 And a cell so defined, he writes a bit later, is doubtlesslycomparable to an amoeba.25

Schultze’s papers provided a new understanding of what the cell is,less morphological than the original conception of the cell as a struc-tural building block, and more concerned with the unity of substance inplants and animals. Protoplasm became the new unifying idea in biol-ogy, championed most notably in the English-speaking world by Tho-mas H. Huxley (1825–1895), who in a public lecture of 1868 described itas ‘‘the physical basis of life’’.26 Protoplasm became popular because itoffered a threefold means of unifying all the various beings of the

21 See Geison (1969a) for a history of the development of the protoplasmic theory.22 Baker, 1952, p. 165; Schultze, 1861, 1863.23 Schultze, 1987 [1861], p. 137. All translations are my own unless otherwise noted.24 Ibid., p. 138.25 Ibid., p. 139. See Brewer (1994) for discussion of Schultze’s investigations of the

amoeboid properties of white blood cells.26 Huxley, 1968 [1868].

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organic world: a unity of substance (the colourless, albuminoid, pro-teinaceous protoplasmic matter itself); a unity of function (irritability,nutrition, division, movement); and a unity of form (essentially a speckof life-slime or jelly, with the capability of producing formed materialssuch as a cell wall or membrane, flagella, cilia, or hard encasing materiallike shell, bone or nails). In this lecture Huxley mentioned the similaritybetween the colourless blood cells and some of the lowest organisms(e.g. change of form and independent creeping movement), and that thehuman animal begins life as a single cell or unit of protoplasm.Although he did not explicitly mention amoeba the allusions were clear,as was an allusion to Haeckel’s purportedly un-nucleated Monera, ofwhich Protamoeba was the type.27

Yet even before Huxley brought the existence of protoplasm to theattention of the general public, the reformed version of the cell theorywas making its way into textbooks. For example, the fourth edition ofWilliam Benjamin Carpenter’s (1813–1885) influential text, AManual ofPhysiology, Including Physiological Anatomy for the Use of the MedicalStudent, which appeared in 1865, featured a new preface introducing thereader to the protoplasmic theory of the cell. Carpenter explained thatthe new edition was required because:

it now appears to be conclusively established that the Cell, with itsmembranous wall, nucleus, and contents, is no longer to be takenas the primitive type of organization; but that the nearest approachto this type is to be found in the segment of ‘protoplasmic sub-stance’ or ‘sarcode’ which forms the entire body of the lowestAnimals: – and further, that the portion of the fabric of even thehighest Animals which is most actively concerned in Nutrition, is aprotoplasmic substance diffused through every part, its segmentsbeing sometimes isolated by the formation of ‘cell-walls’ aroundthem. Hence the study of the life-history of the Rhizopoda, whichtheir ordinarily minute size and transparence renders compara-tively easy, comes to throw a most unexpected light upon thephenomena which occur in the innermost penetralia of the complexorganization of Man.28

In a later section (IV 2) dealing with ‘‘Cells, as Components of theAnimal Fabric’’ Carpenter introduces various types of rhizopods,

27 See Huxley (1968 [1868], p. 140). Huxley actually alludes here to the purported

Moneron Bathybius haeckeli, which upon further inspection proved to be an artifact ofthe techniques used to preserve dredge samples from the ocean floor.28 Carpenter, 1865, p. vii.


including amoeba, and then writes: ‘‘Between the simple body of thesehumble Rhizopods, and the complex fabric of Man and the higherAnimals, there would seem to be but little in common: and yet it ap-pears from recent researches that in the latter, as in the former, theprocess of Formation is essentially carried on by the instrumentality ofprotoplasmic substance, universally diffused through it in such a manneras to bear a close resemblance to the pseudopodial network of theRhizopod’’.29

Carpenter explains elsewhere in the Manual the revolutionary sig-nificance of the protoplasm theory for a philosophical system of biol-ogy. ‘‘It was formerly supposed that vital action could only be exhibitedby organized structure. But we now know that all the functions of Lifemay be carried on by minute ‘jelly-specks,’ in whose apparently-homogenous semi-fluid substance nothing like ‘organization’ can bedetected’’.30 The striking conclusion of the protoplasm theory, in otherwords, was that life is not the result of organization but that organi-zation is the result of this living, formless, slimy substance, proto-plasm.31 The microscopes of the day were unable to reveal anything thatwould correspond to a structure within protoplasm, so it was commonlybelieved to be a homogenous substance. Some drew from this themechanistic conclusion, that life was ultimately reducible to the physicaland chemical properties of the protoplasmic molecules, rendering anyappeal to a vitalistic life-force or Lebenskraft unnecessary.32

Carpenter describes the similarities between amoebae and the col-ourless blood cells of humans: that they both lack a cell membrane andexhibit amoeboid movement by the extension of pseudopodial pro-cesses.33 He would also note in his later work The Microscope and itsRevelations the amoeba-like phagocytic abilities of white blood cells toengulf and devour foreign particles.34 (Figure 2). In this same work

29 Ibid., 142. This is an evident allusion to Schultze’s work on the foraminifera whoselong slender protoplasmic extensions often blend with one another – anastomosing isthe technical term – to form a complex network.30 Ibid., p. 266.31 Compare ‘‘Life, therefore, is not the result of organization, but the reverse’’.

Haeckel, 1878a, p. 84.32 Geison, 1969. Not every supporter of the protoplasm concept drew from it

mechanistic conclusions. Lionel Beale (1828–1906), for instance, who divided the sub-stance of protoplasm into what he called ‘‘Bioplasm’’ – the living substance – and‘‘formed matter’’ – dead material made by the former, was an avid critic of Huxley’s

‘‘physicalism’’ and an outspoken advocate of vitalism. See Strick (2000, chaps. 2–5).33 Carpenter, 1865, pp. 153, 145–146[0].34 Carpenter, 1881, p. 786.

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(Sect. 405) he also discussed the ability of some amoebae to break upinto smaller pieces, each of which was capable of its own independentexistence. This ‘‘extraordinary power to reproduce the entire organismfrom a mere fragment’’35 was taken as a sign of the fundamental vitalnature of protoplasm, and that the ameoba was itself, in a sense, acomposite organism composed of the basic living stuff, protoplasm.

Andrew Mendelsohn states that exemplary materials are ‘‘exemplaryof something far more general and not of the same kind, such as atheory or law (‘‘The morula is exemplary of cell formation by divi-sion’’)’’ whereas typical specimens are characteristic of a species or kind(‘‘This is a typical morula’’).36 Similarly, we can now begin to see howthe ameoba became exemplary of protoplasm, and so of living matter,and of life in general in all its varied forms, from the lowest single-celledorganism to the most complicated multicellular human. It was throughprotoplasm’s new status as the Urstoff of life that amoeba could be seenas exemplary of cells (and of life) in general.37 The amoeba representedprotoplasm in its simplest form, wall-less, undifferentiated, homoge-nous, formless. Protoplasm theory allowed the formless amoeba tostand as the Type of vital unit because it taught that vital activity is not

Figure 2. Mucus-corpuscle from the mucus of the throat showing time-lapsed amoe-

boid motions. From Carpenter (1865, p. 146).

35 Carpenter, 1881, p. 488.36 Mendelsohn, 2003, p. 34.37 It should be noted however that the existence of some kind of original formless

matter (Urschleim) had been floated by Lorenz Oken (1779–1851) as early as 1809 in his

Lehrbuch der Naturphilosophie.


the result of organization or structure, but just the reverse, that orga-nization (e.g. a highly specialized organ from a higher animal) is theresult of the vital activity inherent in the essentially formless proto-plasmic substance. All the basic and essential vital properties (growth,nutrition, movement, reproduction, irritability) are found in protoplasmand in their simplest forms in the amoeba.

The suitability of the amoeba as a stand in for the cell in general wasaided by the physiologist Ernst Brucke (1819–1892), who proposed inan important paper in 1861 that cells be regarded as ‘‘elementaryorganisms’’.38 If cells are organisms in their own right, then the simplesttype of organism – the amoeba – can easily stand in as exemplary ofthese cell-organisms (notwithstanding the fact that cells may exhibit agreat variety of specialized forms when arranged as sub-units of higherplants and animals). I suggest that some biologists were beginning tothink, at least implicitly, according to the following syllogism: The cell isan elementary organism; the amoeba is an elementary organism; ergo,the amoeba = the cell.

Evolution and the Theory of Common Descent

Recall now the statement of the eminent British physiologist Sir MichaelFoster that ‘‘The higher animals, we learn from morphological studies,may be regarded as groups of amoebae peculiarly associatedtogether’’.39 In order to understand fully how it had become possible forFoster to say this, we need to look at another important bit of nine-teenth century theorizing about the unity of life. This is the theory ofevolution or the community of descent. While Charles Darwin (1809–1882) is to be credited for making this idea respectable among nine-teenth-century scientists, Darwin himself had very little to say on thetopic of cells or their similarities to the protozoa. For this topic we mustturn to Darwin’s most enthusiastic German disciple, the zoologist ErnstHaeckel (1834–1919). Haeckel earned his scientific credentials throughextensive studies of unicellular organisms and other lower (typicallymarine) invertebrates. Haeckel’s synthesis of the Darwinian theory ofdescent with contemporary studies of cells and single-celled organismscan be found in his two large early books, the Generelle Morphologie of1866 and the Naturliche Schopfungsgeschichte of 1868.40 Here one finds

38 Brucke, 1861.39 Foster, 1880, p. 4.40 Haeckel, 1866; idem., 1868.

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much discussion of amoebae and other primitive organisms of whatHaeckel called the Protist kingdom, a third kingdom he proposed wasintermediate between and ancestral to the traditional plant and animalkingdoms. Here one is introduced to Haeckel’s Protamoeba, anorganism so primitive and simple it lacked even the differentiation of anucleus (the class of such organisms Haeckel called the Monera, a moreprimitive subdivision of the kingdom Protista). Such a primitiveorganism, Haeckel proposed, offered the best glimpse of what musthave been the earliest ancestor of all living things. Haeckel first spokepublicly in support of Darwin in 1863, at the Stettin meeting of Germanscientists and physicians, where he surmised that the ‘‘the oldestancestral organisms, from which all others have evolved’’, might havebeen ‘‘a Moner, similar to certain amoeboid organisms, which have yetto achieve the level of organization of a cell’’.41

Haeckel was a tireless promoter of evolutionary morphology, anapproach combining elements of typological theory with the theory ofevolution. For Haeckel and other adherents of this program, types werenot to be construed as the eternal, immutable ideal forms of olderidealistic morphologists like Goethe, Cuvier, or Owen, rather they wereforms of organization shared by organisms closely related throughcommon descent from some earlier ancestral organism. Types did notreflect ideal thoughts in the mind of a divine creator, they reflectedshared genealogies.42

In his Anthropogenie of 1874 Haeckel included a chapter entitled‘‘The Ovum and the Amoeba’’, in which he compared the ova of variousanimals to the form of the amoeba (Figure 3). From the fact that allanimals begin in a unicellular form Haeckel concludes, via his famousbiogenetic law that ‘‘ontogeny is a brief and condensed recapitulation ofphylogeny’’, that all animals are descended from a unicellular form; andthat probably there is one such ancestor for all animals. Are there anyforms of life currently existing, he asks, which spend their whole life as asingle cell and can serve as a clue to the nature of this ancient one-celledancestor? Most definitely, he answers, the protists; but he singles out asespecially relevant the amoeba. For the amoeba is, he says, a ‘‘perma-nent ovum’’.43 He then further draws out the amoeba’s significance:

Hence, although the amoeba is nothing but a simple cell, it isevidently able to accomplish all the functions of the multicellular

41 Haeckel, 1863, p. 27.42 Coleman, 1976; Nyhart, 1995; Breidbach, 2002.43 Haeckel, 1874, p. 109.


organism. It moves, feels, nourishes itself, and reproduces....It is forthe following reasons that we regard the amoebae as the unicellularorganisms which have special phylogenetic (or evolutionary)relations to the ovum....[many lower animals have ova very similar

Figure 3. Ova of various animals, executing amoeboid movements. (A1–A4) Sponge;(B1–B8) parasitic crab; (C1–C5) cat; (D) trout; (E) chicken; (F) human. From Haec-kel (1906, p. 45).

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to amoebae: amoeboid motion, phagocytosis, cell division]. It is,therefore, no audacious hypothesis, but a perfectly sound conclu-sion, to regard the amoeba as the particular unicellular organismwhich offers us an approximate illustration of the ancient commonunicellular ancestor of all the metazoa, or multicellular animals.The simple naked amoeba has a less definite and more original[ursprunglicheren] character than any other cell. Moreover, there isthe fact that recent research has discovered such ameoba-like cellseverywhere in the mature body of the multicellular animals.44

Elsewhere, in a semi-popular treatise on the protists, Haeckel said of theamoeba: ‘‘If we seek among the Protists, an organism which at theheight of its development remains a single cell, and represents, the Ideal[Ideal] of the cell, so to speak, we are led before all others to the famousAmoebae’’.45

In Haeckel’s writings then we see the amoeba serving in two roles: (1)as typical or exemplary of ‘the cell’ in its simplest form, indicating a unityof type, and (2) as representative of the ancient ancestor of all livingplants and animals, indicating a unity of descent. What is it though thatmakes the amoeba ‘primitive’? Its lack of permanent form, lack of dif-ferentiation, lack of structure (no mouth, locomotory appendages,stomach, anus etc.), its lack of organization, its lack of any division ofphysiological labour means it exhibits no specialization, all functionsbeing performed by the entire cell (with the exception of the nucleus inthe higher amoeba, these Haeckel considered true cells in contrast withthe ‘cytodes’, or those lacking a nucleus, such as the Protamoeba), andfinally their appearance of a ‘chaotic’ or un-ordered state.

Such were the popular ideas about the amoebae and their significancefor the phylogeny of man when Foster was writing his textbook ofphysiology. Foster was a younger colleague of T. H. Huxley and the twoworked closely together. Foster acted as a demonstrator for two sum-mers (1871–1872) in Huxley’s famous course in elementary laboratorybiology for schoolmasters at South Kensington before taking up anewly established position in physiology at Cambridge.46 The results ofthis summer course can be seen in Huxley’s popular textbook, A Courseof Practical Instruction in Elementary Biology.47 The methodology

44 Ibid., 1874, pp. 111–112.45 Haeckel, 1878a, p. 19. Italics in original.46 See Geison (1978, 130ff) for details of the Kensington summer school, and the book

in general for a study of Foster’s career and approach in physiology. For a briefer studyof Foster, see Geison (1969b).47 Huxley, 1875.


employed by Huxley was to instruct the student by means of laboratorydissection and experimentation on a series of selected organisms whichwere to serve as morphological types of organic organization, allarranged with a decidedly evolutionary perspective in mind. Startingwith sections on yeast and protococcus (a unicellular alga) the thirdsection is devoted to the ‘‘Proteus Animalcule’’ (or Amoeba) and ‘‘theColourless Blood Corpuscles’’. So similar are these two forms of organiclife, the student is told, that one may easily substitute samples fromone’s own blood if no Amoebae are to be found.48 The student is alsoinformed of the closeness in appearance and behaviour between anAmoeba and the blastula cells which make up an early embryo.49

Foster adopted Huxley’s typological perspective when he wrote hisown influential text book of physiology. The first edition of Foster’s AText Book of Physiology appeared in 1877 and went through six editionsand part of a seventh. It played a significant role in spreading theevolutionary approach to physiology in Britain.50 Foster’s chief topic ofphysiological research concerned the source of cardiac rhythm. In hisattempts to understand how the heart beat arises at the cellular levelFoster was impressed by the presence of similar rhythmic phenomena inthe undifferentiated protoplasm of amoebae, which he called contractileamoeboid waves.51

Foster’s textbook of physiology begins with a prolonged discussionof the amoeba. In the introduction he explained the importance of thissimple single-celled organism: ‘‘It thus lives, moves, eats, grows, andafter a time dies, having been during its whole life hardly anything morethan a minute lump of protoplasm. Hence to the Physiologist it is ofinterest, since in its life the problems of physiology are reduced to theirsimplest forms’’.52 After detailing the basic properties of amoeba Foster

48 In the earlier text Lessons in Elementary Physiology (1870) Huxley also emphasizes

the closeness in nature of the white blood corpuscles and the amoebae. See Huxley(1870, pp. 67–69).49 Huxley, 1875, pp. 19–20.50 Geison, 1978, p. 336. I have only had access to the third and fifth editions of

Foster’s Text Book of Physiology, though quotation from and description of the first

edition by Geison (1978, p. 217), indicates that the relevant passages on the higheranimals as collections of amoebae and the focus on the amoeba as the type of a livingbeing were there from the first. The passage describing higher animals as groups of

amoebae is not however included in the fifth edition of 1888.51 See Geison (1969b, 1978) for details.52 Foster, 1880, p. 1. Recall the statement of the earlier British physiologist Thomas

Southwood Smith who wrote in 1827, ‘‘whatever is once ascertained to be true relativeto the elementary organization and action of a living being of any description, will

ultimately be discovered to be true of all...’’. Quoted in Jacyna, 1984, pp. 21–22.

ANDREW REYNOLDS322

writes ‘‘Such are the fundamental vital qualities of the protoplasm of anamoeba; all the facts of the life of an amoeba are manifestations of theseprotoplasmic qualities in varied sequence and subordination’’.53 Thenext paragraph begins with the sentence: ‘‘The higher animals, we learnfrom morphological studies, may be regarded as groups of amoebaepeculiarly associated together. All the physiological phenomena of thehigher animals are similarly the results of these fundamental qualities ofprotoplasm peculiarly associated together. The dominant principle ofthis association is the physiological division of labour corresponding tothe morphological differentiation of structure’’.54 Protoplasm, he ex-plains, possesses all the essential and basic properties of vital activity,even as found in the higher vertebrates and in man. But the higher upthe scale we go the more we find that physiological labour has beendivided among the cells, and in consequence has arisen the variousforms of specialized cell types. ‘‘Hence, in the evolution of living beingsthrough past times, it has come about that in the higher animals (andplants) certain groups of the constituent amoebiform units or cells have,in company with a change in structure, been set apart for themanifestation of certain only of the fundamental properties of proto-plasm, to the exclusion or at least complete subordination of the otherproperties’’.55

For Foster the principle of physiological division of labour is key,and a lack thereof is a sign of primitiveness.56 Since the amoeba isessentially a naked and homogenous clump of protoplasm performingall the vital activities in one cell, it is primitive. And yet the cells of thehigher tissues and organs possess no new properties unknown to theamoeba, it is only that several of these basic properties have been refinedby the division of labour so that the essentially amoeboid cells havebecome specialists in these particular functions.

Foster was even willing to extend this view to the higher mentalfaculties. As he wrote in 1885: ‘‘The doctrine of evolution compels us toadmit that consciousness must be potentially present in the simpleprotoplasm of the amoeba, and must be similarly present in all thetissues of the highly developed animal, instead of being confined to

53 Foster, 1880, p. 4.54 Ibid.55 Ibid.56 Geison (1978, p. 217, n. 35) thinks Foster learned of the physiological principle of

the division of labour through Darwin’s discussion of it in The Origin of Species (1859).On its introduction to biology by Henri Milne-Edwards (1800–1885) and Darwin’s

familiarity with it see Limoges, 1994 and Schweber, 1980.


some limited portion of the nervous system. Evolution refuses to admita sharp line of demarcation between a ‘‘conscious’’ and a ‘‘non-conscious’’ part, and this decision is increasingly supported as ourknowledge of the nervous system advances’’.57

The imputation of sensibility or a rudimentary awareness to amoebaeand to cells in general was not a new claim, as Haeckel had popularizedthe idea of what he called a ‘‘cellular psychology’’ from the late 1870son, and the idea was put into serious experimental practice by his stu-dent Max Verworn (1863–1923).58 Verworn conducted extensive studiesinto the behaviour of single-celled protists and other lower animals, andhis widely read textbook General Physiology opened with the statementthat ‘‘general physiology can be only cell-physiology’’.59 Verworn wasfully committed to the cell theory and the idea that vital activities andproperties are best investigated through their simplest forms. In hisdiscussion of ‘elementary vital phenomena’, he stated that the ‘‘move-ment of Amoeba can serve as a type’’ since ‘‘[t]his organism is the lowestof all living things, and its formless body holds within itself the wholesecret of life’’.60 The French psychologist Alfred Binet (1857–1911) alsopublished a brief survey of the evidence of ‘‘psychic life’’ among themicro-organisms. Of the collected evidence Binet wrote that ‘‘We shallnot regard it as strange, perhaps, to find so complete a psychology in thehistory of the lower organisms, when we call to mind that, agreeably tothe ideas of evolution now accepted, a higher animal is nothing morethan a colony of protozoans’’.61 Within some higher animals, under theinfluence of the division of labour, Binet wrote, ‘‘the cells of the brainare organisms that have been perfected with reference to psychicalattributes’’.62 In the mid-1890s, Jacques-Raphael Lepine, (1840–1919),professor of clinical medicine, and the histologist Mathias Duval (1844–1907), were even suggesting that activity of neurons could be under-stood by analogy with the extension and retraction of pseudopodialprocesses in amoeboid rhizopods63 (Figure 4).

Michael Foster, who had earlier shared the view that single-celledorganisms were especially suited for the investigation of various vital

57 Foster, 1885, p. 20.58 See Haeckel (1878b) and Verworn (1889).59 Verworn, 1899, p. vii. See Verworn (1889) for protist behaviour.60 Verworn, 1899, p. 235.61 Binet, 1910 [1888], p. vii.62 Ibid.63 On this connection see Black (1981). On the study of protist behaviour and psy-

chology see Schloegel and Schmidgen (2002).

ANDREW REYNOLDS324

properties, later had a change of heart. As he explained in 1895 in areview of Verworn’s text of general physiology:

It is not for me who in my rash youth had wild dreams of buildingup a new physiology by beginning with the study of the amoeba,and working upwards, to say one word against the experimentalinvestigation of the lower forms of life. But experience and reflec-tion have shown me that, after all, the physiological world is wise inspending its strength on the study of higher animals.64

Foster had become convinced by this time that lower organisms likeamoeba actually presented more complicated objects of study preciselybecause they lacked the division of labour which isolated and broughtto the surface, as he put it, the vital activities of interest in the spe-cialized tissue cells of higher animals. Because an elementary organismlike amoeba was busy performing all vital functions within its singlecell it was difficult to focus clearly on how it carried out any singleactivity.

Figure 4. Rhizopod and ganglion cell. From Verworn (1889, pp. 76–77).

64 Review of Verworn’s Allg. Physiol., Nature, Vol. 51, p. 530, quoted in Dobell, 1911,

p. 307.


In addition to the studies already mentioned above, amoebae andother rhizopods, such as the foraminifer Gromia oviformis, wereimportant vehicles for studying the basic properties of protoplasm(Figure 5). They served in the late nineteenth century and later as modelorganisms for the investigation of protoplasmic streaming, amoeboidmovement, and the function of the nucleus via experiments in whichamoebae were bisected into nucleated and anucleated portions.65

An inspection of some of the key text books in general physiology,zoology and cytology from around the end of the nineteenth centuryreveals that when the authors wished to include a general illustration ofa cell, they frequently chose a diagram of an amoeba, and very often ofAmoeba proteus, so that A. proteus often stood as the exemplar of theamoeba-type. This is true of Oscar Hertwig’s (1849–1922) Zelle undGewebe (1893), Max Verworn’s Allgemeine Physiologie (1895), and E. B.Wilson’s (1856–1939) The Cell in Development and Inheritance (1896, 1stedition; 1900, 2nd revised and enlarged edition; 1928, 3rd revised andenlarged edition). It is also true of later texts such as Woodruff’sFoundations of Biology (6th ed., 1941, p. 11).66

In Hertwig (1893) the first figure is of a plant cell but the second is ofA. proteus (after Leidy 1879 taken from R. Hertwig); the context of thefigure is a discussion of the properties of protoplasm (Figure 6). InVerworn (1895), the first example of a single-cell individual is a figure ofStentor, but Verworn uses amoeba as an illustration of the groundsubstance of protoplasm, which in the amoeba ‘‘not rarely is completelystructureless’’.67 Wilson’s (1896) first figure shows cells from a devel-oping salamander embryo, and the second is of A. proteus (Figure 7).The text wherein this figure is mentioned explains that though there isgreat diversity of form and structure among various types of cell, ‘‘cellsnevertheless possess a characteristic type of organization common tothem all’’, and ‘‘...in the lowest forms of life the entire body consists ofbut a single cell (Figure 2)’’. In the first chapter (‘‘General Sketch of theCell’’) Wilson included a generalized diagram of a cell of the sort whichhas become standard in modern texts to accompany his discussion ofthe ‘‘General Morphology of the Cell’’.68

65 See Lorch (1973) for details.66 In fact even one of the most currently popular university biology textbooks con-

tinues the tradition of introducing amoeba as representative of single-celled life forms.See Campbell and Reece (2002, p. 2).67 Verworn, 1895, p. 85, Figure 28.68 See Maienschein (1991) for a discussion of Wilson’s use of diagrams and illustra-

tions in the three editions of The Cell and Droscher (2002) for a more general discussion

of Wilson’s views on cell theory.

ANDREW REYNOLDS326

In the second edition of 1900, Wilson inserted a figure of cells fromthe root-tip of an onion (to illustrate the multicellular condition inplants), making the amoeba now the subject of the third figure. Wilsonremarked that the cells of unicellular organisms and the tissue cells ofhigher plants and animals are of the ‘‘same general type’’ and that‘‘Structurally, therefore, the multicellular body is in a certain sense

Figure 5. Gromia oviformis (after Schultze). From Hertwig (1895, p. 30).


comparable with a colony or aggregation of the lower one-celledforms’’.69

Such comparisons between the body of an amoeba, construed as asingle-cell organism, and the differentiated tissue cells of higher plantsand animals were not without their critics, however, most notably theBritish protozoologist Clifford Dobell (1886–1949).70 Dobell’s positionwas that all living things are composed of protoplasm, and that pro-toplasm is sometimes found to be subdivided into units containing anucleus and cytoplasm, while in other cases the protoplasm may contain

Figure 6. Amoeba Proteus (after Leidy) from Richard Hertwig. From O. Hertwig(1893, p. 15).

69 Wilson, 1900, p. 5. The third edition (1925) remained basically unchanged withrespect to the amoeba illustration and the comparison between cells of unicellularorganisms and tissue cells of plants and animals. See Reynolds (2007).70 Dobell, 1911. See Corliss (1989), Jacobs (1989), and Richmond (1989) for discus-

sion of the debates over the legitimacy of comparing unicellular protozoans to the cells

of higher plants and animals.

ANDREW REYNOLDS328

one or more nuclei and is not subdivided into separate units. In theformer case, encompassing the multicellular plants and animals, Dobellallowed that we may speak of a cellular organization. But in the latter,as is typically found in the Protista, he insisted we do not have a single-celled organization, but a non-cellular organization. A cell must beunderstood to be part of an organism, not a whole organism itself.71

The significance, therefore, of a protist like Amoeba, according toDobell, is not that it represents a primitive organism homologous to thecells of higher plants and animals, but a fundamentally different type oforganization in comparison and contrast to the entire body of a mul-ticellular organism.72 Dobell rejected talk of humans being highlyevolved ‘‘colonies’’ or ‘‘states’’ of supposedly ‘‘primitive’’ unicellularamoebae. But in rejecting this ‘‘Amoeba to Man’’ element of the ‘‘celltheory’’ it was not his intention to denigrate Amoeba, but rather toelevate it to a fully equal status as a successfully evolved organism.73

Another critic of the ‘‘cell theory’’ worth noting here is the Austrian-American anatomist Carl Heitzmann (1836–1896). Heitzmann wasvery interested in morphology and the structure of protoplasm, and

Figure 7. Amoeba Proteus (from Sedgwick and Wilson’s Biology). From Wilson

(1900, p. 7).

71 Dobell, 1911, p. 284.72 Ibid., p. 276.73 Ibid., p. 297f.


anticipated some of Dobell’s criticisms concerning the comparison be-tween amoebae and animal cells. He too rejected the claim that higheranimals are composed of separate, autonomous units in light of evi-dence that these so-called cells are typically connected by numerousprotoplasmic ‘‘bridges’’. Heitzmann interpreted this to mean that thefine anatomical structure of a higher animal resembles more a multi-nucleated syncytium common among the protists. Heitzmann’s criticismis highly instructive for our purposes, however, for although he rejectedthe thesis that plants and animals are aggregates of independent cells, hestill regarded the amoeba as the exemplar of living matter. Man is notanalogous to a colony or state of amoeba-like cells, according toHeitzmann, rather ‘‘Man is a complex amoeba’’!74 For Heitzmann,then, the amoeba was exemplary of the unity of life even without theassumption that it represents a single-celled organism.

The Type Concept and the Unity of Life

We have seen now how some biologists came to view the amoeba ascomparable to, not only immature and structurally simple human cellslike ova and early embryo cells, but also to mature and specialized cellssuch as leucocytes and even neurons, the components of that organwhich was supposed to have reached the pinnacle of evolutionaryprogress and complexity, the human brain. A classic expression of thisattitude is summed up by the invertebrate zoologist George JohnAllman (1812–1898), in his 1879 presidential address to the BritishAssociation for the Advancement of Science. In his talk, ‘‘Protoplasmand the Commonality of Life’’, Allman explained how the modernscience of the day had come to recognize the biological significance ofthe amoeba, having shown that ‘‘in this little soft nucleated particle wehave a body whose significance for the morphology and physiology ofliving beings cannot be overestimated, for in Amoeba we have theessential characters of a CELL, the morphological unit of organization,the physiological source of specialized function’’.75 The amoeba, heclaimed, serves as the very ‘‘type’’ of a cell.76 It was in this way that theamoeba could be made to stand in for the cell in almost any biologicalinvestigation or discussion. For instance, when the British physiologistEdward Schafer (later Sir Edward Sharpey-Schafer) (1850–1935) argued

74 Heitzmann, 1883, p. 36.75 Allman, 1879, p. 237.76 ‘‘...in the body of an Amoeba we have the type of a cell’’. Allman, 1879, p. 238.

ANDREW REYNOLDS330

that the essential part of the cell is neither the wall nor membrane(‘‘reticular substance’’), but what is today called the cytoplasm(‘‘interstitial substance’’), his argument drew upon the lack of a‘‘reticular substance’’ in Amoeba and the ‘‘white blood corpuscle’’.77

The guiding principle of this line of reasoning, though only implicitperhaps, is that whatever is true of the very type of a cell must be true ofall its diverse token instantiations. This principle was, as we saw earlier,a central element of the earlier romantic programme to formulate aunified account of life, and it remained an important element of post-Darwinian morphology. As the English zoologist J. Arthur Thomson(1861–1933) explained, writing as late as 1903, ‘‘the morphologist has tofind unity amid manifoldness ... and to recreate the Systema Naturae,not as a mere classification, but as the chart of history’’.78

To better appreciate the task Thomson was describing, we can con-sider the following. Suppose you were asked to choose one organism torepresent life on earth in all its multifarious forms and variety: whatwould it be? A rose? An elephant? A mushroom? None of these partic-ular organisms are general enough to do the job. They all possess fea-tures too specific to represent Life in general. But both the cell theory andthe protoplasm theory were designed by synthesis-seeking biologists withjust this purpose in mind. Consider their tenets: All living things arecomposed of cells/protoplasm; all life properties are properties of cells/protoplasm; all cells/units of protoplasm come from prior cells/units ofprotoplasm. The problem is: which sort of cell, of all the various plantand animal tissue cells, and all the various single-celled organisms, is fitto represent life in general? What features would one look for in such anexemplar? It ought to share essential similarities with all known forms oflife. But in order to do this the exemplar can hardly be a particular itself,its nature must be general. What is needed is a type, an ideal, a kind of‘‘average’’ organism. The amoeba was able to fill this role because it is infact a general, a type, rather than a specific individual or token; it isn’teven a particular species or genus of organism. This is because ‘‘being anamoeba’’ really designates a form of life or habit, viz. crawling about bythe extension of changing pseudopodial processes, and this is a featureshared by many cells across all the major kingdoms.79 Just as there is no

77 Anonymous, 1887. Schafer’s contribution to the Encyclopaedia Britannica article

on Histology also begins with a discussion of the amoeba as an example of the‘‘undifferentiated living substance termed ‘protoplasm’’’. See Schafer (1885, p. 4).78 Thomson, 1903, p. 330.79 Even some ‘‘lower plants’’ (the now defunct division Thallophyta, e.g. algae, fungi,

lichens and bacteria) possess reproductive ‘‘swarmer’’ cells or myxamoebae with

amoeboid features.


‘‘the cell’’, there is no ‘‘the amoeba’’. Both are types, and this allowed theconcept of the amoeba (often instantiated by an individual from any oneof a number of different species of the genus Amoeba or any one of anumber of different ‘‘amoeboid’’ cells) to be exemplary of the concept ofthe cell.

The French biologists Yves Delage (1854–1920) and Edgard Herou-ard (1858–1932) attest to this point in their general zoology text of 1896.In their discussion of the class Rhizopodia [sic] and its morphologicaltype (Type Morphologique), the authors explained, ‘‘The being whichsums up the general characters of the Rhizopods is, in the widest sense ofthe word, the amoeba [amibe]: not the genus Amoeba, but the amoeba ingeneral, the ideal form [forme ideal], which we call amibe for short, in thefeminine and without capital or italics to distinguish it from the genusAmibe (Amoeba), taken as is usual, in the masculine’’.80 It was this ‘‘idealform’’, this ‘‘amoeba in general’’, that many biologists found to be afitting illustration of the protoplasmic cell concept. However, to illustrateit through a material figure required selecting a particular amoeba, andoften Amoeba proteus was chosen for this purpose.81

It is worth noting, perhaps, that evidence from modern molecularbiological studies suggests that amoebae are not the most primitive ofthe protozoans (nor are they a monophyletic group); they are in factbelieved to be derived from an earlier flagellated organism.82 What thismeans is that their apparent ‘‘primitiveness’’, their formlessness, theirmotion by the extension of pseudopodia, is really a derived specializa-tion, an adaptation from a more ‘‘organized’’ and ‘‘complex’’ form oflocomotion (by flagella). This turns on its head in an interesting andinstructive way the popular nineteenth-century conviction that theamoeba represents the starting-point in the evolution of ‘‘order out ofchaos’’.83

80 Delage and Herouard, 1896, Vol. 1, p. 59.81 Consider, by contrast, how modern biology texts often employ artistic illustrations

of ‘‘typical’’ plant and animal cells. These are obviously ideal types, not specificorganisms or organism cells meant to stand as exemplars of a broader class or group.82 Simpson et al., 2002.83 Not all biologists however assumed the amoeboid type to be the most primitive

form of life. Otto Butschli (1848–1920), for instance, specified the flagella-bearingamoebae, or Mastigophora, as the original type. See Butschli (1881). When evolu-tionists spoke of the origin of life or the most ancient life forms they typically turned

to amoeba, not to bacteria, which are recognized today to be the more ancient group.Because bacteria possess a regular shape and many have differentiated locomotorystructures (flagella) they didn’t evoke the same associations of primal chaos as does

the amoeba.

ANDREW REYNOLDS332

Conclusion

A concerted effort to devise a unified theory of life took form in theearly nineteenth century, and with it came debates over which particularmaterials were best suited to exemplify it.84 I have tried to show how,and why, in the latter half of the nineteenth century, the amoeba becamethe exemplary material for the protoplasmic version of the cell conceptand the associated protoplasmic theory of life. Its strengths were itsapparent simplicity and its great generalizability. In its amorphous,protean body a general morphological type and an associated theoryabout the evolution of complexity from primitive homogeneity foundmaterial instantiation. ‘‘The amoeba’’ served as a suitably plasticmedium between the concrete world of living organisms and the idealrealm of concepts and theories about life in general.

Acknowledgments

I would like to thank John T. Bonner, Alastair Simpson, Tom Doak,Alana MacIsaac, Jim Strick for their responses to questions and/orcomments on earlier drafts, and Paul Farber and three anonymousreviewers for their very helpful suggestions. I am grateful to ChristieMacNeil and Kellie White for arranging the image files. Financialsupport for this project was provided by research grants from theSocial Sciences and Humanities Research Council of Canada andCape Breton University.

References

Anonymous, 1887. Report on the 1887 Manchester meeting of the BAAS, Section D –Biology, ‘‘A discussion upon. The Present Aspect of the Cell Question.’’ Nature,p. 592.

Allman, G.J. 1879. ‘‘Protoplasm and the continuity of life.’’ Reprinted in George

Basalla, William Coleman and Robert Kargon (eds.), 1970. Victorian Science: a self-portrait from the Presidential addresses to the British Association for the advancementof Science. Garden City, N.J.: Doubleday & Inc.

Baker, John R. 1952. ‘‘The Cell-theory: A Restatement, History, and Critique. Part III.The Cell as a Morphological Unit.’’ Quarterly Journal of Microscopical Science 93(2):157–190.

Bary, Heinrich Anton de. 1859. ‘‘Die Mycetezoen. Ein Beitrag zur Kenntniss der nie-dersten Thiere.’’ Zeitschift fur wissenschaftliche Zoologie 10: 88–175.

84 Mendelsohn, 2003, p. 34.


Binet, Alfred 1910. The Psychic Life of the Micro-Organisms: A Study in ExperimentalPsychology, second reprinted edition, Chicago: Open Court Press. [Original French

publication in 1888.].Black, Sandra E. 1981. ‘‘Pseudopods and Synapses: the amoeboid theories of neuronal

mobility and the early formulation of the synapse concept, 1894–1900.’’ Bulletin of

the History of Medicine 55: 34–58.Breidbach, Olaf. 2002. ‘‘The former synthesis – Some remarks on the typological

background of Haeckel’s ideas about evolution.’’ Theory in Bioscience 121: 280–296.

Brewer, Douglas B. 1994. ‘‘Max Schultze and the Living, Moving, and PhagocytosingLeucocytes: 1865.’’ Medical History 38: 91–101.

Brucke, Ernst. 1861. ‘‘Die Elementarorganismen.’’ Sitzungsberichte der kaiserliche

Akademie der Wissenschaften. 44. Bd. II.: 381–406.Butschli, Otto. 1881. ‘‘Protozoa’’. in Bronn’s Klassen und Ordnungen des Thierreichs Bd. 1.

Leipzig: C. F. Winter.Campbell, Neil A. and Reece, Jane B. 2002. Biology, 6th ed. Toronto: Benjamin

Cummings.Carpenter, William Benjamin. 1865. A Manual of Physiology, Including Physiological

Anatomy for the Use of the Medical Student, 4th ed. London: John Churchill ([First

edition 1846]).—— 1856. The Microscope and Its Revelations. London: John Churchill.Coleman, William. 1976. ‘‘Morphology between Type Concept and Descent Theory.’’

Journal of the History of Medicine and Allied Sciences 31: 149–175.Corliss, John O. 1989. ‘‘The Protozoon and the Cell: A Brief Twentieth-Century

Overview.’’ Journal of the History of Biology 22: 307–323.Delage, Yves and Herouard, Edgard. 1896. Traite de Zoologie Concrete, Tome I: La

Cellule et Les Protozoaires. Paris: Schleicher.Dobell, C. Clifford. 1911. ‘‘The Principles of Protistology.’’ Archiv fur Protistenkunde

23(3): 269–310.

Droscher, Ariane. 2002. ‘‘Edmund B. Wilson’s The Cell and Cell Theory between 1896and 1925.’’ History and Philosophy of the Life Sciences 24: 357–389.

Ehrenberg, Christian. 1838. Infusionthierchen als vollkomene Organismen. Leipzig:

Leopold Voss.Farber, Paul Lawrence. 1976. ‘‘The Type-Concept in Zoology during the First Half of

the Nineteenth Century.’’ Journal of the History of Biology 9(1): 93–119.

Foster, Michael. 1880. A Text Book of Physiology, 3rd ed., revised. New York: Mac-Millan and Co.

—— 1885. ‘‘Physiology.’’ Encyclopaedia Britannica, 9th ed., Vol. XIX, New York:Scribner’s & Sons, pp. 8–23.

Geison, Gerald L. 1969a. ‘‘The Protoplasmic Theory of Life and the Vitalist-MechanistDebate.’’ Isis 60: 273–292.

—— 1969b. ‘‘Michael Foster.’’ entry in the Dictionary of Scientific Biography, 4: 79–84.

—— 1978. Michael Foster and the Cambridge School of Physiology: The ScientificEnterprise in Late Victorian Society. Princeton: Princeton University Press.

Haeckel, Ernst. 1863. ‘‘Uber die Entwickelungstheorie Darwin’s.’’ reprinted in

Gesammelte Populare Vortrage aus dem Gebiete der Entwickelungslehre. Bonn:Strauss, pp. 1–28.

—— 1866. Die Generelle Morphologie der Organismen. Allgemeine Grundzuge derOrganischen Formen-Wissenschaft, mechanisch begrundet durch die von Charles

Darwins reformierte Deszendenz-Theorie, 2 Bde. Berlin: Georg Reimer.

ANDREW REYNOLDS334

—— 1868. Naturliche Schopfungsgeschichte.Gemeinverstandliche wissenschaftlicheVortrage uber die Entwicklungslehre im Allgemeinen und diejenige von Darwin, Goethe

und Lamarck im Besonderen, uber die Anwendung derselben auf den Ursprung desMenschen und andere damit zussamenhangende Grundfragen der Naturwissenschaften,2 Bde. Berlin: G. Reimer.

—— 1870. Biologische Studien: I Heft: Studien uber die Moneren und andere Protisten,

nebst einer Rede uber Entwickelungsgang und Aufgabe der Zoologie. Leipzig: WilhelmEngelmann.

—— 1874. Anthropogenie oder Entwicklungsgeschichte des Menschen. Gemeinverstan-

dliche Vortrage uber die Grundzuge der menschlichen Keimes- und Stammes-Ges-chichte, 2. Bde. Leipzig: Wilhelm Engelmann.

—— 1878a. Das Protistenreich: Eine populare Uebersicht uber das Formengebiet der

niedersten Lebewesen. Leipzig: Ernst Gunther’s Verlag.—— 1878b. ‘‘Zellseelen und Seelenzellen.’’ Vortrag gehalten am 22 Marz 1878 in der

concordia’’ zu Wien, In Gesammelte Populare Vortrage aus dem Gebiete der Ent-wickelungslehre. Bonn: Emil Strauss.

—— 1906. The Evolution of Man: A Popular Scientific Study. Translated from the 5thenlarged edition of Anthropogenie, edited by Joseph McCabe. New York: PeterEckler.

Heitzmann, Carl. 1883. Microscopical Morphology of the Animal Body in Health andDisease. New York: J. H. Vail & Co.

Hertwig, Oscar. 1893. Die Zelle und die Gewebe, Grundzuge der Allgemeinen Anatomie

und Physiologie. Jena: Gustav Fischer.—— 1895. The Cell: Outlines of General Anatomy and Physiology. Translated by M.

Campbell and edited by Henry Johnstone Campbell. London: Swan Sonnenschein &

Co.Hertwig, Richard. 1902. ‘‘Die Protozoen und die Zelltheorie.’’ Archiv fur Protistenkunde

1: 1–40.Hooke, Robert. 1665. Micrographia: Or Some Physiological Descriptions of Minute

Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon.London: Martyn & Allestry.

Huxley, T.H. 1968 [1868]. ‘‘On the Physical Basis of Life.’’ Collected Essays, Vol. 1.

New York: Greenwood Press, pp. 130–165.—— 1870. Lessons in Elementary Physiology, 4th ed. London: MacMillan and Co.—— 1875. A Course of Practical Instruction in Elementary Biology. London:

MacMillan.Jacobs, Natasha X. 1989. ‘‘From Unit to Unity: Protozoology, Cell Theory, and the

New Concept of Life.’’ Journal of the History of Biology 22(2): 215–242.

Jacyna, L.S. 1984. ‘‘The Romantic Programme and the Reception of Cell Theory inBritain.’’ Journal of the History of Biology 17(1): 13–48.

Jones, Thomas Wharton. 1844. ‘‘Report on the changes in Blood in Inflammation andon the Nature of the Healing Process.’’ British and Foreign Medical Review 18: 225–

280.Kolliker, Albert. 1845. ‘‘Die Lehre von der thierischen Zelle und den einfacheren

thierischen Formelementen, nach den neuesten Fortschritten dargestellt.’’ Zeitschrift

fur wissenschaftliche Botanik 1(2): 46–102.Leidy, Joseph. 1879. Fresh-water Rhizopods of North America. Report of the United

States Geological Survey of the Territories. Washington: Government Printing

Office.


Limoges, Camille. 1994. ‘‘Milne-Edwards, Darwin, Durkheim and the Division ofLabour: A Case Study in the Conceptual Exchanges between the Social and the

Natural Sciences.’’ I.B. Cohen (ed.), The Natural Sciences and the Social Sciences.Boston Studies in the Philosophy of Science. Dordrecht: Kluwer, pp. 317–343.

Lorch, I. Joan. 1973. ‘‘Some Historical Aspects of Amoeba Studies.’’ Jeon Kwang W.

(ed.), The Biology of the Amoeba. New York: Academic Press, pp. 1–36.Maienschein, Jane. 1991. ‘‘From Presentation to Representation in Wilson’s The Cell.’’

Biology and Philosophy 6: 227–254.

Margulis, Lynn, Corliss, John O., Michael, Melkonian and Chapman, David J. 1990.Handbook of Protoctista: The Structure, Cultivation, Habitats and Life Histories ofthe Eukaryotic Microorganisms and Their Descendants Exclusive of Animals, Plants

and Fungi; A guide to the algae, ciliates, foraminifera, sporozoa, water molds, slimemolds and other protoctists. Boston: Jones and Bartlett.

Mendelsohn, J. Andrew. 2003. ‘‘Lives of the Cell.’’ Journal of the History of Biology36: 1–37.

Nyhart, Lynn K. 1995. Biology Takes Form: Animal Morphology and the GermanUniversities, 1800–1900. Chicago: University of Chicago Press.

Owen, Richard. 1855 [1843]. Lectures on the Comparative Anatomy and Physiology of the

Invertebrate Animals, Delivered at the Royal College of Surgeons, 2nd ed. London:Longman, Brown, Green, and Longmans.

Reynolds, Andrew. 2007. ‘‘The Theory of the Cell State and the Question of Cell

Autonomy in Nineteenth and Early Twentieth-Century Biology.’’ Science in Context20(1): 71–95.

Richmond, Marsha L. 1989. ‘‘Protozoa as Precursors of Metazoa: German Cell The-ory and Its Critics at the Turn of the Century.’’ Journal of the History of Biology

22(2): 243–276.Sapp, Jan. 2003. Genesis: The Evolution of Biology. Oxford: Oxford University Press.Schafer, Edward A. 1885. ‘‘Animal Histology’’, section I of Article on Histology.

Encyclopedia Britannica, 9th ed., Vol. XII. New York: Scribner’s & Sons, pp. 4–10.Schloegel, Judy Johns and Schmidgen, Henning. 2002. ‘‘General Physiology, Experi-

mental Psychology, and Evolutionism: Unicellular Organisms as Objects of Psy-

chophysiological Research, 1877–1918.’’ Isis 93(4): 614–645.Schultze, Max. 1987. [1861]. ‘‘Uber Muskelkorpchen und das was man eine Zelle zu

nennen habe.’’ Archiv Anatomische Physiologische wissenschaftlich Medicin, S.1–27:

Reprinted in Klassiche Schriften zur Zellenlehre von Matthias Jacob Schleiden, The-odor Schwann, Max Schultze, eingeleitet und bearbeitet von Ilse Jahn, Leipzig:Akademische Verlagsgesellschaft, Geest & Portig K.-G.

—— 1863. Das Protoplasm der Rhizopoden und der Pflanzenzellen, ein Beitrag zur

Theorie der Zelle. Leipzig: Wilhelm Engelmann (Protozoa, Vol. IV).Schweber, Silvan S. 1980. ‘‘Darwin and the Political Economists: Divergence of

Character.’’ Journal of the History of Biology 13(2): 195–289.

Siebold, Carl von. 1849. ‘‘Uber einzellige Pflanzen und Tiere.’’ Zeitschrift fur wissens-chaftliche Zoologie 1: 270–294 [Reprinted in English translation in Quarterly Journalof Microscopical Science 1(2), 1853, pp. 111–121, 195–206].

Simpson, Alastair G.B. and Roger, Andrew J. 2002. ‘‘Eukaryotic Evolution: Getting tothe Root of the Problem.’’ Current Biology 12: R691–R693.

Strick, James E. 2000. Sparks of Life: Darwinism and the Victorian Debates overSpontaneous Generation. Cambridge, Mass: Harvard University Press.

ANDREW REYNOLDS336

Thomson, J. Arthur. 1903. Progress of Science in the Century, volume XXV in the seriesThe Nineteenth Century. London: Linscott.

Verworn, Max. 1889. Psycho-physiologische Protistenstudien: Experimentelle Unter-suchungen. Jena: Fischer.

—— 1895. Allgemeine Physiologie: Eine Grundriss der Lehre vom Leben. Jena: Fischer.

—— 1899. General Physiology: An Outline of the Science of Life, translated from thesecond German edition and edited by Frederic S. Lee. London: MacMillan and Co.

Weindling, Paul. 1981. ‘‘Theories of the Cell State in Imperial Germany.’’ Charles

Webster (ed.), Biology, Medicine, and Society, 1840–1940. Cambridge: CambridgeUniversity Press, pp. 99–155.

Wilson E.B. 1896. The Cell in Development and Inheritance. London: MacMillan Co.

(2nd ed., 1900; 3rd ed., 1925).


Amoebae as Exemplary Cells: The Protean Nature of an Elementary Organism

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