Apparently the only great biological theory generated 

 in the seventeenth century was the theory of preformation. 

 According to that theory, the embryonic organism is minute 

 at the earliest period of its existence. (10) One of the 

 earliest defenders of this theory was Marcello Malpighi, 

 who considered that in the egg, in a coagulated condition, 

 there is a completely prepared animal which needs for its 

 unfolding a flow of nutrition. 



The preformationists explained that the difficulty or 

 impossibility of seeing parts of the adult creature in 

 the embryo occurs because the organisms are small in number, 

 transparent, and rolled up like balls of thread. The 

 transformation from the apparently uniform homogeneity of 

 the microscopically small embryo to the perceptible 

 polymorphism of the formed organism, i.e. development, was 

 interpreted by the preformists as a thickening of parts and 

 organs, and their development (evolutio) was the untangling 

 of the clew. The etymology of "development" (the origin of 

 this word has been completely lost) undoubtedly finds its 

 origin in preformationist representations. 



Malpighi' s preformationist theory was keenly received 

 by his contemporaries. Embryological works and philosophical 

 writings appeared, their conclusions coinciding to a degree 

 with Malpighi 's. The factual data for supporting preformation 

 was achieved by Jan Swammerdam (1637 - 1685); he reached his 

 conclusions from investigation of metamorphosis in insects 

 and some other arthropods. Apparently, Swammerdam was one 

 of the first to revive the idea of generations of embryos 

 enclosed one within the other. 



The logical consequence of the preformation theory, the 

 doctrine about "enclosing" of embryos, is not considered a 

 creation of the seventeenth century. Its sources can be 

 traced back to the fourth century of our era.^ The philosophers 



The Russian word "razvitie" for "development" (also Latin, 

 "evolutio"; German, "Entwicklung"; English and French, 

 "development" and "developpement"; Italian, "svillupo") 

 means unrolling of anything which was originally wrapped up. 

 See A. D. Nekrasov, 0PL0D0TV0RENIE V ZHIVOTNOM 

 TSARSTVE. ISTORIYA PROBLEMY (Fertilization in the 

 animal kingdom. Historical problems), Moscow, 1930, p. 67. 



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