epigenesis noun. 
[ɛpɪ'dʒɛnɪsɪs] M17.[from EPI- + -GENESIS.]Biology (now 
Hist.). (A theory of) the development of an organism by progressive differentiation of an initially undifferentiated whole (freq. opp. 
preformation). Also (earlier), formation by successive accretion of parts. 
 [TahlilGaran] English Dictionary ▲