[Caspar Friedrich Wolff (1734-1794). The concept of epigenesis and the problem of spontaneous generation].

The link between the notion of epigenesis and that of spontaneous generation does not seem complicated when it is viewed in theoretical terms or when it is approached in a pure model form. However, once any of its particular manifestations in the history of biology is analysed, the interrelationship between the two notions ceases to be unequivocal. One example of that comes with the first fully-fledged concept of epigenesis, based on careful observation of embryonic development, presented by Caspar Friedrich Wolff in the 18th century. The process of development that an act of spontaneous generation has given rise to cannot, of course, be anything else but one of epigenesis. In this sense, epigenesis constitutes a necessary condition for spontaneous generation, but is not a sufficient condition, i.e. not every process of development through epigenesis has at its source an act of spontaneous generation. Evidence that Wolff was inclined towards the concept of spontaneous generation comes from the presence in his works of a notion described by the Latin term ortus (emergence). That notion--together with that of an organic body--is subject to detailed analysis in the current paper. If the process of spontaneous generation is understood as a process of emergence in nature of what is animate and organic, from what is inanimate and non-organic, and as a process in which living beings are not involved, but a living being is its outcome, then the notion of ortus is close in meaning to the notion of spontaneous generation. However, the deistic and theological philosophical foundation of Wolff's concept of epigenesis is in conflict with the notion of spontaneous generation. It seems that Wolff's notion of ortus can be interpreted in two ways. Firstly, it can be interpreted as as result of the theoretical extrapolation in time applied by Wolff to the usual way in which organic bodies emerge (the process is always given rise to by a nonorganic body, supplied by another organic body), all the way back to that the distant moment when the first organic body in time was to emerge; this extrapolation has been reconstructed in detail in the current paper. Secondly, the notion of ortus can be also interpreted as a special kind of heterogenesis, a process which is given rise to by an organic body, but which produces living beings that do not deserve the name of organic bodies--beings that are poorly differentiated in terms of morphology and organization, and thus devoid of distinct species membership, such as simple algae, moulds, internal parasites etc. If that is a correct interpretation, then in neither case would Wolff's ideas have anything to do with real spontaneous generation in the strict sense.