"Essential force" and "formative force": Models for epigenesis in the 18th century

Abstract

For almost a century (1672-1757) at the heart of the scientific revolution the science of the living was quasi exclusively dominated by preformationist theories of generation: these would counter any model implying selforganization of the living and discard any force accounting for the emergence of complex structures1. Preceded by such attempts as Buffons and Maupertuiss, the real restoration of epigenesis came about in 1759 with the Theoria generationis of Caspar Friedrich Wolff (1733-1794). My first objective is to spell out the reasons that enticed Wolff into recasting embryogenesis in accordance with epigenetic concepts. In their own time, Wolffs theses had two consequences: (1) they elicited a decline of classical preformationism; (2) they themselves underwent a "vitalist", or rather "teleomechanist"2, recasting which mitigated their drastic bent. Secondly, I shall focus on this metamorphosis as it came about when Johann Friedrich Blumenbach (1752-1840) set up his vitalist interpretation of epigenesis in ber den Bildungstrieb und das Zeugungsgeschfte (1781)3.© 2006 Springer. Printed in the Netherlands.