Henry Charlton Bastian's support for spontaneous generation is shown to have developed from his commitment to the new evolutionary science of Darwin, Spencer, Huxley and Tyndall. Tracing Bastian's early career development shows that he was one of the most talented rising young stars among the Darwinians in the 1860s. His argument for a logically necessary link between evolution and spontaneous generation was widely believed among those sympathetic to Darwin's ideas. Spontaneous generation implied materialism to many, however, and it had associations (...) in Britain with radical politics and amateur science. Huxley and the X Club were trying to create a public posture of Darwinism that kept it at arm's length from those negative associations. Thus, the conflict that developed when Huxley and the X Club opposed Bastian was at least as much about factional in-fighting among the Darwinians as it was about the experiments under dispute. Huxley's strategy to defeat Bastian and define his position as "non-Darwinian" contributed significantly to the shaping of Huxley's famous address "Biogenesis and Abiogenesis." Rhetorically separating Darwinism from Bastian was thus responsible for Huxley's first clear public statement that a naturalistic origin of life was compatible with Darwin's ideas, but only in the earth's distant past. The final separation of the discourse on the meaning of Brownian movement and "active molecules" from any possible link with spontaneous generation also grew out of Huxley's strategy to defeat Bastian. Clashes between Bastian and the X Club are described at the BAAS, the Royal Society, and in the pages of "Nature" and other journals. (shrink)

With historical hindsight, it can be little questioned that the view of protozoa as unicellular organisms was important for the development of the discipline of protozoology. In the early years of this century, the assumption of unicellularity provided a sound justification for the study of protists: it linked them to the metazoa and supported the claim that the study of these “simple” unicellular organisms could shed light on the organization of the metazoan cell. This prospect was significant, given the state (...) of cytology circa 1910. In the wake of the major gains made in understanding nuclear division in the last two decades of the nineteenth century, cytology was suddenly confronted with many, seemingly less penetrable, problems. Several aspects of nuclear organization still remained unexplained, and recent research had revealed the presence in the cytoplasm of structures whose functions in cell life were unknown. Classical methods of cytology, relying on descriptive, morphological analysis, seemed ill equipped to resolve these questions.Hertwig's program for protozoology, grounded in the assumption of the fundamental unity of organization in protozoa and metazoa, offered a potential means for investigating these and other problems of cell theory. Linked to mainstream cytology, protozoology was advocated as a means of experimentally investigating key biolobical processes — reproduction, metabolism, and organelle morphology and physiology — less accessible in higher organisms. Protozoa were hailed as prime experimental organisms, in which cell structure and function could be more easily studied. Unlike the metazoan cell, they could be subjected to controlled experiments in which the external environment was modified and the effects monitored. Protozoa offered, in other words, a promising experimental means by which to investigate the cell — its structures and its processes.The success of this program within Germany was soon apparent. In contrast to the rather neglected state of the discipline in 1900, protozoology began to be recognized as more than a somewhat obscure area of study for specialists. In practical terms, this translated into greater numbers of students attracted to the field, increased institutional support for the discipline, and its elevation in status within the biological sciences as new developments, particularly in connection with medical applications, began to draw attention to the field.64The unicellular hypothesis also promoted the internal development of the science. It provided a rationale for introducing the various techniques used in cytology, embryology, physiology, and the new field of biochemistry as suitable research tools for protozoology as well. This vastly extended the research possibilities and facilitated the understanding of, among other things, protozoan organization, modes of reproduction, and evolutionary relationships. The new experimental grounding of the discipline in turn fitted in well with developments in biology at large: in contrast to the descriptive methodology that had predominated in the nineteenth century, this new experimental program placed protozoology at the forefront of the early twentieth-century movement to make biology an experimental science comparable to physics and chemistry.Yet the criticism of the unicellular hypothesis can also be seen as having served a valuable function within the development of the discipline. It focused attention on the study of protists as organisms in their own right, not simply as models for metazoan cells. More generally, it helped to remind biologists of the particular evolutionary assumptions that supported this conception. Dobell and other British critics pointed out, among other things, the association between the theory of recapitulation and the interpretation of protozoa as unicellular organisms. At the time when the recapitulation theory and the germ-layer doctrine were in decline, it was important to stress how these evolutionary ideas also entered into the contemporary concepts of subsidiary specialties. This was as true for protozoology as it was for cell theory itself. The chromidial theory, in its various guises, and the binuclearity hypothesis did in fact contain elements of recapitulationist reasoning, and they were open to criticism for the same kind of overly speculative theorizing that characterized this evolution theory. Dobell's critique forced protozoologists and cell theorists alike to review the theoretical postulates guiding their investigations.In the absence of further historical studies, it is hard to evaluate the consequences of this debate in later years. The issue was not whether protozoa were the precursors of metazoa — both sides accepted this. They disagreed over which particular protozoon had served as the ancestral form, and this, in turn, influenced their stance on the question of unicellularity. The situation is little changed today. Because the former question is still an open one, the latter remains so too. Both of the models for the origin of multicellular organisms — colonies of ciliates versus multinucleate protists — are still presented as possible mechanisms in modern textbooks of evolution. Unable to judge the dispute in terms of the ultimate validity of the competing conceptions, the historian requires other criteria. It perhaps becomes more important to evaluate the issues in the context of the internal and external stimulus they provided the discipline.65 In these terms, and from the present historical vantage point, Hertwig's research program for protozoology, based upon the unicellular hypothesis, appears to have been a successful one. (shrink)

The cell theory—the thesis that all life is made up of one or more cells, the fundamental structural and physiological unit—is one of the most celebrated achievements of modern biological science. And yet from its very inception in the nineteenth century it has faced repeated criticism from some biologists. Why do some continue to criticize the cell theory, and how has it managed nevertheless to keep burying its undertakers? The answers to these questions reveal the complex nature of the cell (...) theory and the cell concept on which it is based. Like other scientific ‘laws’, the assertion that all living things are made of cells purchases its universality at the expense of abstraction. If, however, this law is regarded merely as a widely applicable empirical generalization with notable exceptions, it still remains too important to discard. Debate about whether the cell or the organism standpoint provides the more correct account of anatomical, physiological, and developmental facts illustrates the tension between our attempts to express the truth about reality in conceptual terms conducive to a unified human understanding. (shrink)

In the nineteenth century protozoology and early cell biology intersected through the nexus of Darwin's theory of evolution. As single-celled organisms, amoebae offered an attractive focus of study for researchers seeking evolutionary relationships between 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 to human and other metazoan cells made them popular objects of study among morphologists, physiologists, and even those investigating animal behaviour. (...) The amoeba became the exemplar of the new protoplasmic cell concept of mid-century and because its apparent simplicity made it widely generalizable it became a popular subject in a breadth of experimental investigations and theoretical speculations. It was able to do this because "the amoeba" denotes not a particular organism, but a general type of behaviour 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 a progressive development of order from chaos. (shrink)

The ArgumentMicroscopical consideration played a crucial role in German physiology in the period of, grosso modo, 1780–1830. Specifically, a conception of material change was established, according to which all life is grounded in the process of the generation of microscopical forms out of an amorphous, primitive generative substance. Embryological development, tissue growth, and the generation of microorganisms were all considered to be the manifestation of this fundamental developmental process. In contrast to the common historiography, I try to understand Theodor Schwann's (...) 1838 discovery of the cell theory in terms of the epistemological categories he applied to the prevailing conceptions of life and living matter. I argue that Schwann was able to discern cells not because of any superior microscopical methods, but rather as part of his wider investigative endeavor to explicate life processes according to specific causal agents. I argue that Schwann was able to demonstrate the existence of cells only when he considered animal tissues in terms of a causal relation between specific material agents and their effect, that is, the developmental history of tissue. (shrink)

The cell is not only the structural, physiological, and developmental unit of life, but also the reproductive one. So far, however, this aspect of the cell has received little attention from historians and philosophers of biology. I will argue that cell theory had far-reaching consequences for how biologists conceptualized the reproductive relationships between germs and adult organisms. Cell theory, as formulated by Theodor Schwann in 1839, implied that this relationship was a specific and lawful one, that is, that germs of (...) a certain kind, all else being equal, would produce adult organisms of the same kind, and vice versa. Questions of preformation and epigenesis took on a new meaning under this presupposition. The question then became one of whether cells could be considered as autonomous agents producing adult organisms of a given species, or whether they were the product of external, organizing forces and thus only a stage in the development of the whole organism. This question became an important issue for nineteenth-century biology. As I will demonstrate, it was the view of cells as autonomous agents which helped both Charles Darwin and Gregor Mendel to think of inheritance as a lawful process. (shrink)

The cell is not only the structural, physiological, and developmental unit of life, but also the reproductive one. So far, however, this aspect of the cell has received little attention from historians and philosophers of biology. I will argue that cell theory had far-reaching consequences for how biologists conceptualized the reproductive relationships between germs and adult organisms. Cell theory, as formulated by Theodor Schwann in 1839, implied that this relationship was a specific and lawful one, that is, that germs of (...) a certain kind, all else being equal, would produce adult organisms of the same kind, and vice versa. Questions of preformation and epigenesis took on a new meaning under this presupposition. The question then became one of whether cells could be considered as autonomous agents producing adult organisms of a given species, or whether they were the product of external, organizing forces and thus only a stage in the development of the whole organism. This question became an important issue for nineteenth-century biology. As I will demonstrate, it was the view of cells as autonomous agents which helped both Charles Darwin and Gregor Mendel to think of inheritance as a lawful process. (shrink)

SynopsisThe response to physics and chemistry which characterized mid-nineteenth century physiology took two major directions. One, found most prominently among the German physiologists, developed explanatory models which had as their fundamental assumption the ultimate reducibility of all biological phenomena to the laws of physics and chemistry. The other, characteristic of the French school of physiology, recognized that physics and chemistry provided potent analytical tools for the exploration of physiological activities, but assumed in the construction of explanatory models that the organism (...) involved special levels of organization and that there must, in consequence, be special biological laws.The roots of this argument about concept formation in physiology are explored in the works of Theodor Schwann, Johannes Müller, François Magendie and Claude Bernard among others. (shrink)

The now-classic Metaphors We Live By changed our understanding of metaphor and its role in language and the mind. Metaphor, the authors explain, is a fundamental mechanism of mind, one that allows us to use what we know about our physical and social experience to provide understanding of countless other subjects. Because such metaphors structure our most basic understandings of our experience, they are "metaphors we live by"--metaphors that can shape our perceptions and actions without our ever noticing them. In (...) this updated edition of Lakoff and Johnson's influential book, the authors supply an afterword surveying how their theory of metaphor has developed within the cognitive sciences to become central to the contemporary understanding of how we think and how we express our thoughts in language. (shrink)

We began our survey at a time when Ehrenberg's functional principles concerning the design of all organisms prevailed in interpreting the taxonomic place and internal structure of Infusoria. Other options existed, such as Dujardin's sarcode theory and Siebold's cellular analogy, but these were not persuasive for reasons both relevant to and in addition to the microscopic observations. By mid-century other considerations, including the continuing search for complex life cycles and manifestations of sex, dictated the microscopist's rendering of infusorians. Müller and (...) his students saw spermatozoa and gonads; Stein envisioned alternating generations and generative nuclei; Balbiani found sexual behavior in the events of conjugation; and all interpreted the nuclei and nucleoli as gonads or gonadal products. Evolutionary theory provided a fourth dimension. Obsessed with phylogenies, particularly when joined with the germ-layer theory of development, Haeckel emphasized a structural interpretation and found a considerably altered cell theory ready to fill the breach.By the mid-1870s advances in cytology secured Siebold's original analogy. Infusorians now became single-celled organisms, the first in a long phylogenetic sequence that led to the “highest” metazoans. The analogy allowed Bütschli to invoke another biological principle, the physiological division of labor, to reinterpret the origin of the bisexual state. The ghost of Ehrenberg's polygastric theory had completely vanished. (shrink)