No evolution, no heredity, just development-Julius Schaxel and the end of the Evo-Devo agenda in Jena, 1906-1933: a case study.

Julius Schaxel is an almost forgotten figure in the history of early twentieth century biology. By focusing on his life and work, I would like to illustrate several central developments in that period of history of biology. Julius Schaxel was an early representative and organizer of theoretical biology, discussing and criticizing both Wilhelm Roux's mechanism and Hans Driesch's vitalism. In addition to his theoretical work, Schaxel also did experimental research on developmental issues to support his critique. In this paper, special emphasis is made on the negotiating practice of Schaxel, which he used to establish a new area of biological research and a new audience for that area. In contrast to these new fields, Schaxel can be also portrayed as the endpoint of a research tradition investigating ontogeny and phylogeny together, which today is called Evo-Devo. Following Garland Allen's dialectical processes that led to the decline of the Evo-Devo research agenda, Schaxel's example is used to investigate these processes.