Infusoria: New Prospects for the History of Life

Infusoria captured the attention and imaginations of naturalists and philosophers in the years at the turn of the nineteenth century. From Georges-Louis Leclerc de Buffon and Denis Diderot through Erasmus Darwin to Gottfried Reinhold Treviranus and Lorenz Oken—a diversity of figures explored, experimentally and conceptually, the presence of vital molecules or simple beings at the boundary of the living and nonliving. Experiments on spontaneous generation were repeated again and again, with each new set of trials calling into question earlier results. It remained unresolved whether infusoria were newly existent beings or vestiges of life already there. Many naturalists regarded infusoria as transitional entities complicating distinctions between the organic or inorganic. Many naturalists also regarded infusoria as the composite parts of more complex organisms, like fragments of polyps, that enabled living beings to transform and to regenerate their form. Infusoria thus became important for imagining the development and evolution of life. This paper looks at the place of infusoria in Gottfried Reinhold Treviranus’s Biology and Lorenz Oken’s Naturphilosophie in particular. It explores how their study of these active and animate material entities introduced new prospects for the history of life.