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Summary
In 1979, Robert C. Olby published an article titled ‘Mendel no Mendelian?’, in which he questioned commonly held views that Gregor Mendel (1822–1884) laid the foundations for modern genetics. According to Olby, and other historians of science who have since followed him, Mendel worked within the tradition of so-called hybridists, who were interested in the evolutionary role of hybrids rather than in laws of inheritance. We propose instead to view the hybridist tradition as an experimental programme characterized by a dynamic development that inadvertently led to a focus on the inheritance of individual traits. Through a careful analysis of publications on hybridization by Carl Linnaeus (1707–1778), Joseph Gottlieb Koelreuter (1733–1806), Carl Friedrich Gärtner (1772–1850), and finally Mendel himself, we will show that this development consisted in repeated reclassifications of hybrids to accommodate anomalies, which in the end allowed Mendel to draw analogies between whole organisms, individual traits, and ‘elements’ contained in reproductive cells. Mendel's achievement was a product of normal science, and yet a revolutionary step forward. This also explains why, in 1900, when the report he gave on his experiments was ‘rediscovered’, Mendel could be read as a ‘Mendelian’.
This paper has profited from discussions with John Dupré, Barry Barhnes, Maureen O'Malley, and Hans-Jörg Rheinberger. Staffan Müller-Wille would like to thank the Arts and Humanities Research Board for generous funding, and the ESRC Research Centre for Genomics in Society at the University of Exeter for its hospitality.
Notes
1Michel Foucault, L'ordre de discours. Leçon inaugurale au collège de France prononcée le 2 décembre 1970 (Paris, 1971), 35–37; see also Georges Canguilhem, ‘L'objet de l'histoire des sciences’, In Études d'histoire et de philosophie des sciences concernant les vivants et la vie, 7th edition (Paris, 1994; originally published 1968), 9–23.
2On the various interpretations that historians of science and scientists have provided on Mendel, see Jan Sapp, ‘The Nine Lives of Gregor Mendel’, MendelWeb (1990). Available online at: http://www.mendelweb.org/MWsapp.html (accessed 28 September 2006).
3Vitezslav Orel, Gregor Mendel: The First Geneticist (Oxford, 1996). On Mendel and contemporary biology, see Margaret Campbell, ‘Mendel's Theory: Its Context and Plausibility’, Centaurus 26 (1983), 38–69, Sander Gliboff, ‘Gregor Mendel and the Laws of Evolution’, History of Science 37 (1999), pp. 217–35, and Roger Wood and Vitezslav Orel, ‘Scientific Breeding in Central Europe During the Early Nineteenth Century: Background to Mendel's Later Work’, Journal of the History of Biology 38 (2005), 239–72.
4Robert C. Olby, Origins of Mendelism, 2nd edition (Chicago, 1985); Vitezslav Orel, ‘Constant Hybrids in Mendel's Research’, History and Philosophy of the Life Sciences 20 (1998), 291–99.
6Gregor Mendel, ‘Experiments in Plant Hybridisation’, in Gregor Mendel. Experiments in Plant Hybridisation, with commentary and assessment by the late Ronald A. Fisher, edited by James H. Bennett (Edinburgh, 1965), 7–51 (10). This edition of Mendel's 1866 paper is a reprint of the translation of C. T. Druery, commissioned by the Royal Horticultural Society of Great Britain, and published in its Journal in 1901. The president of the Society at the time was William Bateson, and he reprinted the Druery's translation in his Mendel's Principles of Heredity: A Defense (Cambridge, MA, 1902), pp. 40–95. We will therefore refer to this translation as Bateson's in the following.
5François Jacob, La logique du vivant (Paris, 1970), 201–4. Carl Correns emphasized that Mendel's choice of pea varieties was especially at odds with Carl Nägeli's idea that such varieties were not viable in nature; see Carl Correns, ‘Gregor Mendels Briefe an Carl Nägeli 1866–1873. Ein Nachtrag zu den veröffentlichten Bastardisierungsversuchen Mendels’, in Gesammelte Abhandlungen zur Vererbungswissenschaft aus periodischen Schriften 1899–1924 (Berlin, 1924, originally published 1905), 1233–97 (1234). See also Bentley Glass, ‘Heredity and Variation in the Eighteenth Century Concept of the Species’, in Forerunners of Darwin, 1745–1859, edited by Bentley Glass, Oswei Temkin, and William L. Strauss (Baltimore, MD, 1959), 144–72; Hans Stubbe, Kurze Geschichte der Genetik bis zur Wiederentdeckung der Vererbungsregeln Gregor Mendels, Genetik: Grundlagen, Ergebnisse und Probleme in Einzeldarstellungen 1 (Jena, 1965), 108; Leslie C. Dunn, A Short History of Genetics: The Development of Some of the Main Lines of Thought: 1864–1939 (New York, 1965), 18 (quoting Correns); Peter J. Bowler, The Mendelian Revolution: The Emergence of Hereditarian Concepts in Modern Science and Society (Baltimore, MD, 1989), 99; Robert C. Olby, ‘Mendel, Mendelism, and Genetics’, MendelWeb (1990). Available online at: http://www.mendelweb.org/MWolby.html (accessed 23 October 2006).
7Augustine Brannigan, ‘The Reification of Mendel’, Social Studies of Science 9 (1979), 423–54 (424); Robert C. Olby, ‘Mendel no Mendelian?’, History of Science 17 (1979), 53–72 (67); L.A. Callender, ‘Gregor Mendel: An Opponent of Descent with Modification’, History of Science 26 (1988), 41–75 (72); Floyd V. Monaghan and Alain F. Corcos, ‘The Real Objective of Mendel's Paper’, Biology and Philosophy 5 (1990), 267–92 (268). For a critical discussion of these papers, see Vitezslav Orel and Daniel L. Hartl, ‘Controversies in the Interpretation of Mendels Discovery’, History and Philosophy of Life Sciences 16 (1994), 436–55.
8Olby (note 7), 67.
9Mendel (note 6), 18; cf. Gregor Mendel, ‘Versuche über Pflanzen-Hybriden’, Verhandlungen des Naturforschenden Vereines in Brünn 4 (1865, published 1866), 3–47 (14). For explanations, see note 142 below.
10On this distinction, see Staffan Müller-Wille and Hans-Jörg Rheinberger, ‘Heredity: The Production of an Epistemic Space’, in Heredity Produced: At the Crossroad of Biology, Politics, and Culture, 1500–1870, edited by Staffan Müller-Wille and Hans-Jörg Rheinberger (Cambridge, MA, in press), 3–34 (13).
11Mendel (note 6), 10.
13Carl Linnaeus, Genera plantarum eorumque characteres naturales [. . .] (Leyden, 1737), ‘Ratio operis’, par. 5 (unpaginated). The criterion of constancy had already been used by John Ray (1627–1605) in 1686 to distinguish specific differences from individual variations; see John Ray, Historia plantarum species hactenus editas aliasque insuper multas noviter inventas & descriptas complectens [. . .], 3 vols (London, 1686), I, 40.
12James L. Larson, Interpreting Nature: The Science of Living Form from Linnaeus to Kant (Baltimore, MD, 1996), 61–65.
14Ernst Mayr's claim, that Mendel ‘had little idea what a species was’ must be seen against the background that for Mayr there was one true species concept only: his own biological species concept; see Ernst Mayr, The Growth of Biological Thought: Diversity, Evolution and Inheritance (Cambridge, MA, 1982), 712–13.
15See Wood and Orel (note 3) for a recent overview over the discussions in the Sheep Breeders’ Association and how it influenced Mendel.
16Olby (note 4), 205–7.
17Gliboff (note 3), 219.
18Mendel (note 6), 10.
19Alongside Art, Mendel (note 9) (36–37, 39) also used the expression Species to refer to what he otherwise called ‘good species’ (gute Arten), that is to plant kinds distinguished from each other by a whole set of traits.
20This is especially palpable in the translation edited by Curt Stern and Eva R. Sherwood, where ‘Art’ is almost consistently rendered as ‘variety’, ‘strain’ etc., unless it is clear from the context that Mendel was indeed intending ‘good’ species; see Gregor Mendel, ‘Experiments on Plant Hybrids’, in The Origin of Genetics: A Mendel Source Book, edited by Curt Stern and Eva R. Sherwood (San Francisco, 1966). We are therefore using, with one exception only (note 94), R. A. Fisher's re-edition of Bateson's 1901 translation, which is truer to the original in this respect.
22Linnaeus (1751) 1764 (note 21), 32–33.
21Carl Linnaeus, ‘Disquisitio de sexu plantarum’, in Caroli Linnaei Ammoenitates academicae, seu Dissertationes variae Physicae, Medicae, Botanicae antehac seorsim editae, 2nd edition, edited by Johann Christian Daniel Schreber, 10 vols (Erlangen, 1788–1790), X (1790, essay originally published 1760), 100–31 (126–27); for a detailed reconstruction of this experiment, see Staffan Müller-Wille, ‘“Varietäten auf ihre Arten zurückführen”: Zu Carl von Linnés Stellung in der Vorgeschichte der Genetik’, Theory in Bioscience 117 (1998), 346–76. Olby mentions that Linnaeus produced a second hybrid, Veronica maritima × Verbena officinalis, by manual cross-fertilization, and calls this combination ‘extremely unlikely’ (Olby 1985 [note 4], 4). The source he offers in support for this, a passage translated from Linnaeus’ essay Generatio ambigena (1759), does not provide evidence, however, that this cross was indeed artificially produced (ibid., 142). As a matter of fact, in his first report on the Veronica × Verbena hybrid, Linnaeus only mentions that he had ‘picked it up (lecta)’ not far from the garden beds where the two parent species grew; see Carl Linnaeus, ‘Plantae Hybridae’, in Caroli Linnaei Ammoenitates academicae, seu Dissertationes variae Physicae, Medicae, Botanicae antehac seorsim editae, 7 volumes (Stockholm, 1749–1769), III (1764, essay originally published 1751), 28–62 (35).
23Linnaeus (1751) 1764 (note 21), 30.
24Carl Linnaeus, ‘Metamorphoses plantarum’, in Caroli Linnaei Amoenitates academicae, seu Dissertationes variae Physicae, Medicae, Botanicae antehac seorsim editae, 2nd edition, edited by Johann Christian Daniel Schreber, 10 volumes (Erlangen, 1785–1789), VI (1788, essay originally published 1755), 367–86 (380).
25For instance, in the ‘bigeneric’ case of Veronica spuria (speedwell), allegedly a hybrid of V. maritima and Verbena officinalis, and a few others; see Linnaeus (note 21), nos 1, 3, 6, 4, 18, 23, 29.
26For instance, in the ‘bigeneric’ case of Veronica spuria (speedwell), allegedly a hybrid of V. maritima and Verbena officinalis, and a few others; see Linnaeus (note 21), nos 50.
27For a more detailed account of Linnaeus's classification of hybrids see Müller-Wille (note 21), 366–68.
28Joseph Gottlieb Koelreuter, Dritte Fortsetzung der Vorläufigen Nachricht von einigen das Geschlecht der Pflanzen betreffenden Versuchen und Beobachtungen (Leipzig, 1766), 37; see also Olby 1985 (note 4), 4.
29Conway Zirkle, The Beginnings of Plant Hybridization, Morris Arboretum Monographs, 1 (Philadelphia, 1935), 7–41.
30For a more detailed analysis see Staffan Müller-Wille, ‘Nature as a marketplace: The political economy of Linnaean botany’, in Oeconomies in the Age of Newton, edited by Neil De Marchi and Margaret Schabas, History of Political Economy Supplement 35 (Durham, NC, 2003), 154–72.
31Joseph Gottlieb Koelreuter, Vorläufige Nachricht von einigen das Geschlecht der Pflanzen betreffenden Versuchen und Beobachtungen (Leipzig, 1761), 38.
32Koelreuter must have heard of Linnaeus hybids much earlier already. He had studied natural history with Johan Georg Gmelin at the University of Tübingen, and Gmelin was a close correspondent of Linnaeus, and had devoted his inaugural address in 1749 to the topic of hybridization; see Ernst Mayr, ‘Joseph Gottlieb Koelreuter's contributions to biology’, Osiris, 2nd Series, 2 (1986), 135–76 (136–37). Gmelin, on the other hand, had been inspired to write his essay by Linnaeus, who in 1744 had reported peloric mutations from a wild population of Linaria and had speculated about their hybrid origin. As Linnaeus was unable to reproduce these plants in his garden, they did not play a role in his later writings on hybridization, until 1760, when he finally succeeded in propagating them asexually; see Müller-Wille (note 21) on this.
33Olby (note 4), 9; according to Mayr (note 32), 135, Koelreuters experiments started in 1760 only.
34Koelreuter (note 31), 41–42. In his prize essay of 1760, Linnaeus maintained that he had ‘abraded the pollen [of the seed plant] by hand’ (Linnaeus [1760] 1790 [note 21], 126), while the account from the essay Generatio ambigena, published a year earlier, reported that Linnaeus ‘strongly blew into’ the flowers of the seed plant to remove the pollen; see Carl Linnaeus, ‘Generatio ambigena’, in Caroli Linnaei Amoenitates academicae, seu Dissertationes variae Physicae, Medicae, Botanicae antehac seorsim editae, 7 volumes (Stockholm, 1749–1769), vol. VI (1763, essay originally published 1759), 1–16 (12). If this is true—which is likely, as the essay was composed as a dissertation pro exercitio by Linnaeus’ student Christian Ludwig Ramström who probably witnessed the act—it would have been a ludicrously unreliable method to avoid self-pollination. It is also probable, however, that Koelreuter's suspicion was based on the fact that the plants growing from the seed sent by Linnaeus segregated.
39Koelreuter (note 35), 47–48.
35Joseph Gottlieb Koelreuter Fortsetzung der Vorläufigen Nachricht von einigen das Geschlecht der Pflanzen betreffenden Versuchen und Beobachtungen (Leipzig, 1763), 9.
36Cf. Olby (note 4), 10–18.
37Koelreuter (note 35), 60.
38Koelreuter (note 28), 37.
42Koelreuter (note 31), 44; ‘some’ in all probability indicates Linnaeus.
40Koelreuter (note 35), 58.
41The term Gattung designated species in eighteenth-century German, other than in modern German, where it designates genus. For ‘genus’, Geschlecht was used, while Art, corresponding to ‘species’ in modern German, was used to refer to kinds in general; see Christoph Girtanner, Über das kantische Prinzip für die Naturgeschichte (Göttingen, 1796), 6–10.
46Koelreuter (note 28), 85–86; translation partly based on Mayr (note 32), 170.
43Koelreuter (note 28), 35.
44Koelreuter (note 35), 46; (note 28), 35.
45Koelreuter (note 35), 44.
47Mayr (note 32), 170.
48See ibid., 154–72, and Larson (note 12), 71–76, for detailed accounts of Koelreuter's ‘alchemical’ theory of inheritance.
49Koelreuter employed the same strategy when dealing with an experimental result that formed the inverse of that just discussed. In crossing two kinds of Cucurbita (cucumber), which he had expected to behave like ‘natural’ species and thus to prove sterile, Koelreuter acquired perfectly fertile offspring. He accounted for this by declaring that the parental forms were ‘essentially as little different as a lap-dog and an English mastiff’; see Koelreuter (note 28), 119.
50Koelreuter (note 35), 62.
51Olby (note 4), 25.
52Zirkle (note 29), ch. 3.
53Olby (note 4), 23–26.
54For overviews, see Herbert F. Roberts, Plant Hybridization before Mendel (Princeton, NJ, 1929); Conway Zirkle, Gregor Mendel and his predecessors, Isis 42 (1951), 97–104; Stubbe (note 5); and Larson (note 12), ch. 3. It should be emphasized, that a large amount of observations on hybridizations from the late eighteenth and nineteenth century, in continuing the Linnaean tradition, was probably made in taxonomic and biogeographical literature.
55Augustin Sageret, 1826, ‘Considérations sur la production des hybrides, des variantes et des variétés en général, et sur celles des Cucurbitacées en particulier’, Annales des Sciences Naturelles, 1. Ser., 8 (1826), 294–314 (300–302).
56William Herbert, Amaryllidaceae: Preceded by an Attempt to Arrange the Monocotyledonous Orders, and Followed by a Treatise on Cross Bred Vegetables (London, 1837), 17; on Herbert, see Abigail Lustig, ‘Cultivating Knowledge in Nineteenth-Century English Gardens’, Science in Context 13 (2000), 155–81.
58Carl Friedrich Gärtner, Versuche und Beobachtungen über die Bastarderzeugung im Pflanzenreich (Stuttgart, 1849), 151.
57Carl Friedrich Gärtner, Versuche und Beobachtungen über die Bastarderzeugung im Pflanzenreich (Stuttgart, 1849), x.
59Carl Friedrich Gärtner, Versuche und Beobachtungen über die Bastarderzeugung im Pflanzenreich (Stuttgart, 1849), 163; translation partly based on Olby (note 4), 33.
62Gärtner (note 57), 186.
60Gärtner (note 57), 166.
61Gärtner (note 57), 168.
63Gärtner (note 57), 502–17.
64Gärtner (note 57), 518.
65Gärtner (note 57), 405.
66Gärtner (note 57), 539.
67Gärtner (note 57), 577.
68Gärtner (note 57), 576–77.
69Gärtner (note 57), 578–79.
70See Olby (note 4), 26–31.
71Gärtner (note 57), 581.
72This was also the research programme of Charles Naudin (1815–1899) and Max Ernst Wichura (1817–1866); see Olby (note 4).
73Larson (note 12), 97.
74Gärtner (note 57), 234–35.
75Olby (note 4), 33.
76Gärtner (note 57), 254.
77Olby (note 7), 67.
78Callender (note 7), 41; with varying emphasis, these verdicts have been restated more recently by Monaghan and Corcos (note 7) and B.E. Bishop, ‘Mendel's Opposition to Evolution and to Darwin’. Journal of Heredity 87 (1996), 205–13.
79Mendel (note 6), 7; translation slightly altered. The term ‘Entwicklung’ in early nineteenth-century German covered both ontogeny and phylogeny; see Gliboff 1999 (note 3), pp. 225–26, who suggests to translate it as evolution, in line with English usage at Mendel's time.
80In contrast to what Monaghan and Corcos (note 7), 271, have claimed.
81Gärtner (note 57), 428.
82Gärtner (note 57), 446.
83It should be noted, however, that this step was made possible in the context of a large-scale change in the notion of ‘generation’, which included Gärtner, and comprehended early-nineteenth century biological and social sciences in their entirety. While generation before the nineteenth century signified the procreation of individuals, it came to acquire the subsidary meaning of a population of individuals living at about the same time; see Ohad Parnes, ‘On the shoulders of generations: The new epistemology of heredity in the nineteenth century’, in Heredity Produced: At the Crossroad of Biology, Politics, and Culture, 1500–1870, edited by Staffan Müller-Wille and Hans-Jörg Rheinberger (Cambridge, MA, in press).
84It is in fact easy to identify the different kinds of hybrids that Mendel produced in his experiments by Gärtner's classification: Mendel's ‘hybrids’ (what we would call F1 today) correspond to Gärtner's simple hybrids, Mendel's ‘first hybrid generation’ (what we would call F2 today), resulting from the selfing of hybrids, corresponds to Gärtner's ‘mediated hybrids’. And Mendel's backcrosses would fall under Gärtner's ‘mixed’ and ‘combined’ hybrids, respectively.
85Gärtner himself pointed this out explicitly; see Gärtner (note 57), 516–17.
86Mendel (note 6), 8; translation slightly altered. The term ‘Probe’ (Mendel [note 9], 4) is translated misleadingly in both English translations: as ‘results’ in Bateson's translation (Mendel [note 6], 8) and as ‘attempt’ in Stern's and Sherwood's translation (Mendel [note 20], 2).
88Mendel (note 6), 11; translation slightly altered.
87Mendel (note 6), 10.
91Mendel (note 6), 21.
89Again, this contrasts with what Monaghan and Corcos 1990 (note 7), 271, have claimed with respect to the quoted passage; cf. Raphael Falk and Sahotra Sarkar, ‘The Real Objective of Mendel's Paper: a Response to Monaghan and Corcos’. Biology and Philosophy 6 (1991), 447–51 (449).
90See especially the discussion of the dihybrid series in Mendel (note 9).
92Mendel (note 6), 19; Mendel's emphasis.
93Correns (note 5), 1238. In a similar vein, Mendel emphasized ‘that as an empirical worker I cannot understand anything else by becoming constant as the retention of characters during the period of observation’ (ibid., 1242). Falk and Sarkar (note 88), 449, observe that Mendel neglected properties that are typical of hybrids, namely luxuriance and variegation (heterosis), although he noticed them. In a speculative reconstruction of Mendel's experiments, in the main undertaken to explain why Mendel's results appeared to be ‘too good to be true’ to a number of modern geneticists—a claim going back to Ronald A. Fisher, ‘Has Mendel's Work Been Rediscovered?’ Annals of Science 1 (1936), 115–37—Frederico di Trocchio put forward the hypothesis, that Mendel made his monohybrid crosses ‘just on paper’, extracting the data from experiments, that actually involved polyhybrid crosses throughout; see Frederico di Trocchio, ‘Mendel's Experiments: A Reinterpretation’, Journal of the History of Biology 24 (1991), 485–519. This procedure would have presupposed that Mendel systematically focused on character pairs and neglected all other peculiarities that the individual hybrid plants may or may not have exhibited.
95Mendel (note 20), 15; we have chosen the translation offered by Curt Stern and Eva R. Sherwood in this instance, because William Bateson's translation corrupts the German original. It supposes that it is the seeds that possess ‘one or other of the differing characters’ (Mendel [note 6], 21), while the German original clearly speaks of ‘Hybriden je zweier differierender Merkmale’, that is, in literal translation, ‘hybrids of two differing characters severally’.
94Mendel (note 6), 22–23.
96Callender (note 7), 52. In fact, Callender maintained that Mendel distinguished two laws, ‘(a) “the law of simple combination of characters”, and (b) “the law of combination of different characters”’, the first presumably applying to monohybrid, the latter to polyhybrid crosses. However, Mendel mentions ‘the law of simple combination of characters (Gesetze der einfachen Combinierung der Merkmale)’ with reference to an example of a polyhybrid cross (Mendel [note 9], 32). And the ‘law of combination of different characters’ is a mistranslation in the Bateson translation (on which Callender relied) for ‘law of combination of differing (differierenden) characters’ (Mendel [note 6], 37; cf. Mendel [note 9], 32; Mendel [note 20], 32, provides a correct translation). All in all, Mendel used the term ‘law (Gesetz)’ 15 times in his paper, in one instance qualifying it as a ‘law of development (Entwicklungs-Gesetz)’ (Mendel [note 9], 32). In all instances, the context makes it clear that he was thinking of one law only, the law governing the formation of hybrid offspring which he identified as a desideratum from the outset of his paper, and the law that he did eventually discover to be valid for Pisum. See Gliboff (note 3), pp. 225–28, on Mendel's notion of a ‘law of development’.
97Cf. Monaghan and Corcos (note 7); Orel and Hartl (note 7).
98Mendel (note 6), 21–22. Curt Stern considered this as the first instance in which ‘a problem not only of genetics of individuals and their progeny, but also of a whole population’ was attacked; see Curt Stern, ‘Mendel and Human Genetics’, in G. Mendel Memorial Symposium 1865–1965: Proceedings of a Symposium Held in Brno in August 4–7 1965, edited by M. Sosna (Prague, 1965), 199–218 (204).
99Mendel (note 6), 22–23 (translation slightly altered). We use the technical terms ‘monohybrid’ and ‘polyhybrid’ for the sake of convenience. They were not used by Mendel who referred to mono- and polyhbrid crosses in descriptive terms like the ones contained in the quote.
102Mendel (note 6), 27; translation slightly altered.
100Cf. Orel (note 3), 162–63.
101Cf. Falk and Sarkar (note 88), 450.
104Mendel (note 6), 27–28; Mendel's emphasis.
103This is also the gist of Ivan Fedorovitch Schmalhausen's (1849–1894) summary of Mendel's findings in the formers 1874 dissertation on plant hybrids; see Vitezslav Orel, ‘Response to Mendel's Pisum Experiments in Brno since 1865’, Folia Mendeliana 8 (1973), 199–209. An excerpt from Schmalhausens dissertation is translated in Olby (note 4), 225–26.
105Mendel (note 6), 29 (translation slightly altered).
106Bateson ([note 6], 67) added a footnote to the quoted paragraphs stating: ‘This and the preceding paragraph contain the essence of the Mendelian principles of heredity’.
107Mendel was working with seed characters in the polyhybrid crosses and back-crosses that form the context of his statements on the reproductive cells of hybrids. In this case, the characters of the progeny (F2) do indeed show up ‘in connection with’ the mother-plant (F1) already.
108This does not mean that egg and pollen cells must be identical; they are ‘of like kind’ in so far as their union, all else being equal, invariably brings about the same kind of organism.
109Cf. Olby (note 7), 67.
114Mendel (note 6), 35; Mendel's emphasis.
110Cf. J. Heimans, ‘Mendel's Ideas on the Nature of Hereditary Characters’, Folia Mendeliana 6 (1971), 91–98 (97); Olby (note 7), 58; Orel (note 3), 171–72.
111Mendel (note 6), 31; translation slightly altered. Bateson translation has ‘proving’ for ‘prüfen’, which is simply wrong.
112William Bateson remarked in a footnote to the first English translation of Mendel's paper that Mendel ‘with true penetration, avoids speaking of the hybrid character as “transmitted” by either parent, thus escaping the error pervading modern views of heredity’; see Bateson (note 6), 49. Indeed, according to the law of segregation, hybrids of F1 do produce ‘constant’ forms in F2, and hybridity is therefore not a property that is inherited.
113Callender ([note 7], 53) has maintained that Mendel distorted the views of Koelreuter and Gärtner. While Mendel ascribed to them the statement that ‘hybrids are inclined to revert to the parental forms’, Gärtner and Koelreuter ‘stated categorically that Reversion [sic] was both necessary and inevitable’. Mendel was, however, quoting Gärtner and Koelreuter correctly; see, e.g., Joseph Gottlieb Koelreuter, Zweyte Fortsetzung der Vorläufigen Nachricht von einigen das Geschlecht der Pflanzen betreffenden Versuchen und Beobachtungen (Leipzig, 1764), 82; Gärtner (note 57), 446. The emphasis in speaking about a tendency or inclination to revert was not on denying the necessity of that process, but on stressing its gradual nature, dependent as it were, according to Koelreuter and Gärtner, on the interaction of reproductive forces. We will come back to this point later on.
115Cf. Heimans (note 109); Olby (note 7), 59–62; Orel (note 3), 177.
116Orel and Hartl (note 7), 435–43.
117Mendel (note 6), 43.
119Mendel (note 6), 43.
120Mendel (note 6), 43; Mendel's emphasis.
118In fact, such semi-quantitative statements abounded in the hybridization literature before Mendel; see Roberts (note 54) and Stubbe (note 5) for useful overviews.
121Mendel (note 6), 44–45.
122As pointed out above already, the term for ‘composition’ used by Mendel in the German original—Beschaffenheit—is neutral about what it is exactly that determines this or that ‘composition’. One should not conclude, therefore, that Mendel thought in terms of particulate inheritance. The reproductive cells might differ by overall qualities rather than constituents, for example. This is as true for them as it is for the plants that grow from them.
123As pointed out above already, the term for ‘composition’ used by Mendel in the German original—Beschaffenheit—is neutral about what it is exactly that determines this or that ‘composition’. One should not conclude, therefore, that Mendel thought in terms of particulate inheritance. The reproductive cells might differ by overall qualities rather than constituents, for example. This is as true for them as it is for the plants that grow from them., 48; cf. Gärtner ([note 57], 463) for the original quote.
124Gärtner (note 57), 251; for a translation see to Olby (note 4), 157.
125Gärtner (note 57), 458.
126Mendel (note 6), 49; translation slightly altered.
127Cf. Gärtner (note 57), 14–15, 249–50.
128Mendel (note 6), 51. Mendel mentions ‘Aquilegia atropupurea and canadensis, Dianthus Caryophyllus, chinensis and japonicus, Nicotiana rustica and paniculata’.
129Mendel (note 6), 41–42; Mendel's emphases.
130Mendel (note 6), 25.
131In 1886, C. W. Eichling, a horticulturalist, visited Mendel and asked him how peas growing in the latter's garden had been ‘reshaped in height as well as in type of fruit’. Mendel simply answered: ‘It is just a little trick, but there is a long story connected with it which it would take too long to tell’ (quoted according to Olby [note 4], 90).
132Cf. Callender (note 7), 54–55. To conclude from that, as Callender does (ibid., 72), that Mendel ‘stated clearly that he accepted the general fixity of species’ goes to far, however.
133Mendel (note 6), 45.
134Mendel (note 6), 45; Mendel's emphasis.
135Mendel (note 6), 45. Callender ([note 7], 57) maintained that Mendel was again misrepresenting Gärtner's views here, because the latter added a remark to his list of ‘constant’ hybrids according to which ‘there was always a steady loss of fertility and a general breaking up of the species’ (cf. Gärtner [note 57], 421–22). Callender was wrong, however, to ascribe to Gärtner the general view that ‘species hybrids were invariably sterile’. We demonstrated above that Gärtner was cautious to make such far-reaching empirical claims, and Mendel was therefore right to take the list as Gärtner announced it, namely as a list of ‘exceptionally fertile hybrid plants propagat[ing] themselves with no change of type, like pure species’. The German word that Callender translates with ‘steady’, moreover, is ‘allmählig’, meaning ‘slowly’ or ‘gradually’, rather than steady.
136Mendel (note 6), 47.
137Mendel (note 6), 45–46. Mendel had become acquainted with contemporary cell theory through the teaching of Franz Unger, who relied on the work of Matthias Jacob Schleiden (1804–1881) and Nägeli; see Vitezslav Orel, ‘The teachings of J. M. Schleiden and its possible influence on G. Mendel’, Janus 66 (1979), 33–47, and Olby (note 4), 199–207.
138Mendel (note 6), 46.
139Mendel (note 6), 47; translation slightly altered.
140Mendel (note 6), 46–47; cf. Orel (note 3), 170. Olby ([note 7], 66), has argued that it is in these remarks that Mendel shows himself to be ‘in conflict with classical Mendelian genetics’. We will come back to this point in our conclusions.
141Mendel ([note 6], 46); Mendel's emphasis.
142Mendel to Nägeli, 18 April 1867, translated from Correns (note 5), 1243. This is the second instance in which Mendel used derivatives of the german term ‘erben’ to indicate that something was not inherited. The other instance was in his 1866 paper (Mendel [note 8], 18; cf. Mendel [note 9], 14). There, Mendel stated with reference to the occasional bleaching of green coloration in Pisum seeds:
The cause of this partial disappearance of the green colouring has no connection with the hybrid-character of the plants, as it likewise occurs in the parental variety (Stammpflanze). This peculiarity [bleaching] is also confined to the individual and is not inherited (vererbt) by the offspring.
143Gregor Mendel, ‘Über einige aus künstlicher Befruchtung gewonnene Hieraciumbastarde’. Verhandlungen des Naturforschenden Vereines in Brünn 8 (1869, published in 1870), 26–31 (28).
144Cf. Callender (note 7), 58–59.
145Cf. Callender (note 7), 58–70. Callender's claim, that Mendel also found evidence for the non-constancy of hybrid offspring in Hieracium, although he failed to report this in his published paper (ibid., 63), is based on a misreading, however: where Mendel reported in a letter to Nägeli, dated 4 May 1868, that the hybrid offspring (F2) of H. praealtum and H. stoloniflorum ‘are uniform in structure [. . .] and resemble the hybrid seed plant (Bastard-Mutterpflanze)’ (Correns [note 5], 1259), Callender reads Mendel's ‘hybrid seed plant’ as referring to the ‘maternal parent of the hybrid’. In Mendel's terminology, however, ‘parental species’ are never designated as ‘hybrid’. ‘Hybrid seed plant’ referred to the plants from which the seed for hybrid offspring (F2) was gathered, that is, to what Mendel called hybrids (F1), not to members of the parental generation (P).
146Mendel (note 142), 365. Some handwritten notes from later experiments indicate, that Mendel in the end succeeded to account for the polymorphism of Hieracium hybrids as a result of segregation of multifactorial traits; see Orel (note 3), 187.
147Mendel (note 142), 364.
148Mendel (note 142), 367.
149Cf. J. Heimans, ‘Mendel studying the theorem of the golden section’, Folia Mendeliana 13 (1978), 235–42.
150Mendel (note 6), 47; translation slightly altered.
151Mendel (note 6), 47.
152Mendel (note 6), 48.
153Correns (note 5), 1270.
154Olby (note 4), 254.
155A similar view was expressed by R. A. Fisher in his introduction to Mendel (note 6), 4.
156In a more recent re-assessment of his 1979 paper, Olby distinguishes between methodological and theoretical aspects of Mendel's achievements: ‘By introducing the statistical approach and combinatorial mathematics into the subject of hybridization alongside his concept of the character-pair Mendel surely earned his place’.
157We doubt, therefore, Gliboff's tentative conclusion that ‘to Mendel himself, the goal of the research and the principal message of the paper was the law, not the mechanism’, although we agree with Gliboff that this appeared so to his ‘Austro-Ungerian reader[s]’; see Gliboff (note 3), p. 228.
158Jean Gayon, ‘From Measurement to Organization: Â Philosophical Scheme for the History of the Concept of Heredity’, in The Concept of the Gene in Development and Evolution: Historical and Epistemological Perspectives, edited by Peter Beurton, Raphael Falk and Hans-Jörg Rheinberger (Cambridge, MA, 2000), 69–90 (77–78). On the nineteenth-century conception of heredity as a force, which was especially prevalent among breeders, see Jean Gayon and Doris T. Zallen, ‘The role of the Vilmorin Company in the Promotion and Diffusion of the Experimental Science of Heredity in France, 1840–1920’, Journal of the History of Biology 31 (1998), 241–62.
159See, for example, Onno G. Meijer, ‘Hugo de Vries no Mendelian?’, Annals of Science 42 (1985), 189–232, on de Vries, and Olby (note 4) on William Bateson.
160Frederic L. Holmes, Reconceiving the Gene: Seymour Benzer's Adventures in Page Genetics (New Haven, CT, 2006), ch. 1. Arguably, the various efforts to make sense out of Mendel's paper played a major role in the early history of this struggle. ‘In the achievement of that “progress”’, sociologists of science Barry Barnes, Devid Bloor, and John Henry argue, ‘the misinterpretations of “Mendel's theory” were part of that creative use of the realist mode of speech which engendered adaptation and elaboration of Mendel, movement beyond Mendel, “advance upon” Mendel’; see Barry Barnes, John Henry, David Bloor, Scientific Knowledge: A Sociological Analysis (Chicago, 1996), 96.
161On our reading, then, Mendel's concept of ‘elements’ or ‘factors’ came close to what Lenny Moss has called the preformationist notion of the gene (‘gene-p’), without, however, conflating it with the developmental notion of the gene (gene-d), as many twentieth-century geneticists did; see Lenny Moss, What Genes Can't Do (Cambridge, MA, 2003), ch. 1. On genes as difference makers, see C. Kenneth Waters, ‘What was classical genetics?’, Studies in History and Philosophy of Science 35 (2004), 83–89.
162James Griesemer has argued on this basis that neither Mendel nor his twentieth-century followers ever separated development from heredity as many commentators—most prominently Iris Sandler and Laurence Sandler, ‘A conceptual ambiguity that contributed to the neglect of Mendel's paper’, History and Philosophy of the Life Sciences 7 (1985), 3–70—have maintained. ‘Genetic theories are theories of development’, Griesemer says, ‘but they are theories expressed in terms of developmental invariants’; see James Griesemer, ‘Reproduction and the Reduction of Genetics’, in The Concept of the Gene in Development and Evolution: Historical and Epistemological Perspectives, edited by Peter Beurton, Raphael Falk and Hans-Jörg Rheinberger (Cambridge, MA, 2000), 240–85 (261).
163Gliboff (note 3), p. 223.
164On the diversity of agendas of Mendel's ‘rediscoverers’ Bateson, Correns, de Vries, and Tschermak, see Ilse Jahn, ‘Zur Geschichte der Wiederentdeckung der Mendelschen Gesetze’, Wissenschaftliche Zeitschrift der Friedrich-Schiller Universität Jena, Mathematisch-naturwissenschaftliche Reihe 7 (1958), 215–27, and Olby (note 4), ch. 6.
165Staffan Müller-Wille, ‘Early Mendelism and the Subversion of Taxonomy: Epistemological Obstacles as Institutions’, Studies in History and Philosophy of Biological and Biomedical Sciences 36 (2005), 465–87 (475–77).
166Staffan Müller-Wille, ‘Early Mendelism and the Subversion of Taxonomy: Epistemological Obstacles as Institutions’, Studies in History and Philosophy of Biological and Biomedical Sciences 36 (2005), 70. Callender does not refer to Kuhn. His interpretation of Mendel seems more inspired by viewing history as an eternal struggle between theological and secular world views.
167Olby ([note 7], 55) does not discuss Kuhn's work, but uses the expression ‘paradigm’ to designate the ‘canonical ideas’ invoked by twentieth-century interpretations of Mendel's work. Brannigan ([note 7], 449–51) discusses Kuhn in a long footnote. Brannigan's conclusion that ‘Mendel's work figured as normal science in the hybridist tradition, while in 1900 the revival of Mendel's discovery of segregation constituted a relatively revolutionary achievement’ (ibid., 424) comes very close to our own, with the important difference, however, that we regard the ‘revolutionary achievement’ of Mendel as a product of the ‘normal science’ he was engaged in.
168Thomas S. Kuhn, ‘Second Thoughts on Paradigms’, in The Essential Tension: Selected Studies in Scientific Tradition and Change (Chicago, 1977), 293–319.
169Cf. Hans-Jörg Rheinberger and Staffan Müller-Wille, ‘Gene’, in Stanford Encyclopedia of Philosophy, Winter 2004 edition, edited by E.N. Zalta. Available online at: http://plato.stanford.edu/entries/gene/ (accessed 28 September 2006).
170See, for example, Thomas S. Kuhn, ‘Logic of Discovery or Psychology of Research’, in The Essential Tension: Selected Studies in Scientific Tradition and Change (Chi cago, 1977), 266–92 (272). For an interpretation of Kuhn that emphasizes this aspect, see Barry Barnes, T. S. Kuhn and Social Science (New York, 1982).
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