Source : Webster's Revised Unabridged Dictionary (1913)

Kenogenesis \Ken`o*gen"e*sis\, n. [Gr. ? new + E. genesis.]
   (Biol.)
   Modified evolution, in which nonprimitive characters make
   their appearance in consequence of a secondary adaptation of
   the embryo to the peculiar conditions of its environment; --
   distinguished from palingenesis. [Written also
   {c[ae]nogenesis}.]

Source : WordNet®

caenogenesis
     n : introduction during embryonic development of characters or
         structure not present in the earlier evolutionary history
         of the strain or species (as addition of the placenta in
         mammalian evolution) [syn: {cenogenesis}, {kenogenesis},
         {cainogenesis}, {kainogenesis}] [ant: {palingenesis}]