This essay aims to shed new light on the relations between physiology and psychology in the late nineteenth and early twentieth centuries by focusing on the use of unicellular organisms as research objects during that period. Within the frameworks of evolutionism and monism advocated by Ernst Haeckel, protozoa were perceived as objects situated at the borders between organism and cell and individual and society. Scholars such as Max Verworn, Alfred Binet, and Herbert Spencer Jennings were provoked by these organisms to (...) undertake experimental investigations situated between general physiology and psychology that differed from the physiological psychology advocated by Wilhelm Wundt. Some of these investigations sought to locate psychological properties in the molecular structure of protoplasm; others stressed the existence of organic and psychological individuality in protozoa. In the following decades, leading philosophers such as Friedrich Nietzsche, Charles Sanders Peirce, and Henri Bergson, as well as psychological researchers like Sigmund Freud, integrated the results of these investigations into their reflections on such problems as the nature of the will, the structure of the ego, and the holistic nature of the reactions of organisms to their environment. (shrink)

In 1853, the young Thomas Henry Huxley published a long review of German cell theory in which he roundly criticized the basic tenets of the Schleiden-Schwann model of the cell. Although historians of cytology have dismissed Huxley's criticism as based on an erroneous interpretation of cell physiology, the review is better understood as a contribution to embryology. "The Cell-theory" presents Huxley's "epigenetic" interpretation of histological organization emerging from changes in the protoplasm to replace the "preformationist" cell theory of Schleiden and (...) Schwann (as modified by Albert von Kölliker), which posited the nucleus as the seat of organic vitality. Huxley's views influenced a number of British biologists, who continued to oppose German cell theory well into the twentieth century. Yet Huxley was pivotal in introducing the new German program of "scientific zoology" to Britain in the early 1850s, championing its empiricist methodology as a means to enact broad disciplinary and institutional reforms in British natural history. (shrink)

Rudolf Leuckart's 1851 pamphlet Ueber den Polymorphismus der Individuen (On the polymorphism of individuals) stood at the heart of naturalists' discussions on biological individuals, parts and wholes in mid-nineteenth-century Britain and Europe. Our analysis, which accompanies the first translation of this pamphlet into English, situates Leuckart's contribution to these discussions in two ways. First, we present it as part of a complex conceptual knot involving not only individuality and the understanding of compound organisms, but also the alternation of generations, the (...) division of labor in nature, and the possibility of finding general laws of the organic world. Leuckart's pamphlet is important as a novel attempt to give order to the strands of this knot. It also solved a set of key biological problems in a way that avoided some of the drawbacks of an earlier teleological tradition. Second, we situate the pamphlet within a longer trajectory of inquiry into part-whole relations in biology from the mid-eighteenth century to the present. We argue that biological individuality, along with the problem-complexes with which it engaged, was as central a problem to naturalists before 1859 as evolution, and that Leuckart's contributions to it left a long legacy that persisted well into the twentieth century. As biologists' interests in part-whole relations are once again on the upswing, the longue durée of this problem merits renewed consideration. (shrink)

Rudolf Leuckart’s 1851 pamphlet Ueber den Polymorphismus der Individuen stood at the heart of naturalists’ discussions on biological individuals, parts and wholes in mid-nineteenth-century Britain and Europe. Our analysis, which accompanies the first translation of this pamphlet into English, situates Leuckart’s contribution to these discussions in two ways. First, we present it as part of a complex conceptual knot involving not only individuality and the understanding of compound organisms, but also the alternation of generations, the division of labor in nature, (...) and the possibility of finding general laws of the organic world. Leuckart’s pamphlet is important as a novel attempt to give order to the strands of this knot. It also solved a set of key biological problems in a way that avoided some of the drawbacks of an earlier teleological tradition. Second, we situate the pamphlet within a longer trajectory of inquiry into part-whole relations in biology from the mid-eighteenth century to the present. We argue that biological individuality, along with the problem-complexes with which it engaged, was as central a problem to naturalists before 1859 as evolution, and that Leuckart’s contributions to it left a long legacy that persisted well into the twentieth century. As biologists’ interests in part-whole relations are once again on the upswing, the longue durée of this problem merits renewed consideration. (shrink)

Throughout the last quarter of the nineteenth century, researchers became increasingly interested in explaining the ways in which mammalian teeth, especially molars, and their complex arrangements of cusps arose along both developmental and evolutionary timescales. By the 1890s, two theories garnered special prominence; the tritubercular theory and the concrescence theory. The tritubercular theory was proposed by Edward Drinker Cope in 1883, and later expanded by Henry Fairfield Osborn in 1888, while the concrescence theory was developed by Carl Röse in 1892. (...) Reviews concerning the evolution of mammalian molar teeth tended to paint the two theories as occupying opposing sides, and debates arose between their main proponents; however, their tenets do not seem logically incompatible. Throughout this paper, I argue that the conflict that arose was due not to the content of the theories, but to a diverse array of commitments Cope, Osborn, and Röse held, which turned into background assumptions within the setting of these theories. This history traces the context in which Cope, Osborn, and Röse developed the tritubercular and concrescence theories, and the ways in which the assumptions that these investigators held influenced their perceptions of their theories. (shrink)

In historical literature, Edouard van Beneden is mostly remembered for his cytological discoveries. Less well known, however, is that he also introduced evolutionary morphology – and indeed evolutionary theory as such – in the Belgian academic world. The introduction of this research programme cannot be understood without taking both the international and the national context into account. It was clearly the German example of the Jena University that inspired van Beneden in his research interests. The actual launch of evolutionary morphology (...) at his University of Liège was, however, also connected with the dynamic of Belgian university reforms and the local rationale of creating a research “school.” Thanks to his networks, his mastering of the rhetoric of the “new” biology, his low ideological profile and his capitalising on the new academic élan in late-19th century Belgium, van Beneden managed to turn his programme into a local success from the 1870s onwards. Two decades later, however, the conceptual underpinnings of evolutionary morphology came under attack and the “Van Beneden School” lost much of its vitality. Despite this, van Beneden’s evolutionary morphology was prototypical for the research that was to come. He was one of the first scientific heavyweights in Belgium to turn the university laboratory into a centre of scientific practice and the hub of a research school. (shrink)