The theory of generation that Buffon developed in 1749 in the Histoire naturelle générale et particulière was aimed at restoring epigenesis against preformation which had up to then prevailed, but within the framework of a micro-mechanist physiology. Buffon referred to explanatory concepts like "organicmolecule" and "internal mould" which conformed to that methodological trend, but whose purelyconjectural nature was immediately queried by contemporary opponents as well as supporters of epigenesis. In fact, Buffon attempted to unite "by virtue of analogies" the available observational data on reproductive processes and thus reach for general effects expressive of laws governing the phenomena; but, at the same time, he appealed to hypothetical mechanist models to account for the system formed by the induced general effects. This process paralleled the one J.T. Needham would describe in 1750 in the Nouvelles Observations microscopiques. While tradition has tended to include both in the same critique, these systems, based on distinct, if complementary, empirical data, notably diverged. They supposed relatively distinct methodological and theoretical explanatory principles. The way they conceived the forces responsible for the formation, operation and reproduction of living organisms, differed. Buffon and Needham would therefore offer alternative epigenetic frameworks for conceiving the dynamic processes ruling over the production and replication of organic bodies. These alternatives could be related to a certain opposition between mechanist and vitalist models of the living being during the Enlightenment. Starting from the distinct epistemological profiles of Buffon and Needham's theories of generation, might we determine their respective impact on the quest for a unified theory of living beings?The theory of generation that Buffon developed in 1749 in the Histoire naturelle générale et particulière was aimed at restoring epigenesis against preformation which had up to then prevailed, but within the framework of a micro-mechanist physiology. Buffon referred to explanatory concepts like "organicmolecule" and "internal mould" which conformed to that methodological trend, but whose purelyconjectural nature was immediately queried by contemporary opponents as well as supporters of epigenesis. In fact, Buffon attempted to unite "by virtue of analogies" the available observational data on reproductive processes and thus reach for general effects expressive of laws governing the phenomena; but, at the same time, he appealed to hypothetical mechanist models to account for the system formed by the induced general effects. This process paralleled the one J.T. Needham would describe in 1750 in the Nouvelles Observations microscopiques. While tradition has tended to include both in the same critique, these systems, based on distinct, if complementary, empirical data, notably diverged. They supposed relatively distinct methodological and theoretical explanatory principles. The way they conceived the forces responsible for the formation, operation and reproduction of living organisms, differed. Buffon and Needham would therefore offer alternative epigenetic frameworks for conceiving the dynamic processes ruling over the production and replication of organic bodies. These alternatives could be related to a certain opposition between mechanist and vitalist models of the living being during the Enlightenment. Starting from the distinct epistemological profiles of Buffon and Needham's theories of generation, might we determine their respective impact on the quest for a unified theory of living beings?The theory of generation that Buffon developed in 1749 in the Histoire naturelle générale et particulière was aimed at restoring epigenesis against preformation which had up to then prevailed, but within the framework of a micro-mechanist physiology. Buffon referred to explanatory concepts like "organicmolecule" and "internal mould" which conformed to that methodological trend, but whose purelyconjectural nature was immediately queried by contemporary opponents as well as supporters of epigenesis. In fact, Buffon attempted to unite "by virtue of analogies" the available observational data on reproductive processes and thus reach for general effects expressive of laws governing the phenomena; but, at the same time, he appealed to hypothetical mechanist models to account for the system formed by the induced general effects. This process paralleled the one J.T. Needham would describe in 1750 in the Nouvelles Observations microscopiques. While tradition has tended to include both in the same critique, these systems, based on distinct, if complementary, empirical data, notably diverged. They supposed relatively distinct methodological and theoretical explanatory principles. The way they conceived the forces responsible for the formation, operation and reproduction of living organisms, differed. Buffon and Needham would therefore offer alternative epigenetic frameworks for conceiving the dynamic processes ruling over the production and replication of organic bodies. These alternatives could be related to a certain opposition between mechanist and vitalist models of the living being during the Enlightenment. Starting from the distinct epistemological profiles of Buffon and Needham's theories of generation, might we determine their respective impact on the quest for a unified theory of living beings?