To speak of a « turning point » and a « historical delay » naturally makes the prehistory of the confluence of cellular theory and reproduction theories all the more interesting. What complicates things for such prehistory is that the basic categories used today for reproductive analysis – especially preformation and epigenesis – cannot simply be moved backwards. As long as the exact nature of the relationship between the fertilized egg and the adult organism was not yet defined, preformation and epigenesis must have meant very different things. As Churchill warned other historians of biology long ago, any analysis of these two slippery terms « must become entangled with these persistent questions about the meaning of `novelty,` `origin,` `becoming,` and `form` in a given period (Churchill, 1970, p. 171). What should be taken, for example, from the fact that William Harvey (1578-1657), so well known for reviving Aristotle`s epigenetic theory of embryonic formation, claimed in his De generatione animalium (1651) that « the plant primordium from which the fetus is made […] exists » (Harvey, 1857, p. 465)? And what about the fact that Réne Descartes, with his notorious penchant for the animal machine, called male and female seeds substances that « serve each other as yeast, » the interaction of which led to the formation of one organ after another (Descartes, 1986-1991, vol. 11, p. 253)? The modern version of cell theory includes the following ideas: The idea that all cells come from pre-existing cells, however, had already been proposed by Robert Remak; It was suspected that Virchow plagiarized Remak and gave him no recognition. .