Biology. (formerly) the theory that the individual, with all its parts, preexists in the germ cell and grows from microscopic to normal proportions during embryogenesis (opposed to epigenesis).
Main Entry: pre·for·ma·tion Pronunciation: "prE-for-'mA-sh&n Function: noun : a now discredited theory in biology that every germcell contains the organism of its kind fully formed and complete in all its parts and that development involves merely an increase in size from microscopic proportions to those of the adult—compare EPIGENESIS —pre·for·ma·tion·ist/-sh&-n&st/noun or adjective
[pree-fawr-mey-shuh
n] 