|1.||Compare preformation the widely accepted theory that an individual animal or plant develops by the gradual differentiation and elaboration of a fertilized egg cell|
|2.||the formation or alteration of rocks after the surrounding rock has been formed|
|3.||alteration of the mineral composition of a rock by external agents: a type of metamorphism|
epigenesis ep·i·gen·e·sis (ěp'ə-jěn'ĭ-sĭs)
The theory that an individual is developed by successive differentiation of an unstructured egg rather than by a simple enlarging of a preformed entity.