The idea that activity and interaction among structures and functions is necessary to embryonic development. In the theory of embryological development by Wilhelm Roux (1850-1924), which he referred to as mosaic development, the developing organism proceeds through a stage of independent development directed almost independently of other embryonic regions (i.e., self-differentiation), to be followed by a stage of dependent development during which functional connections are made, and which is dependent on complex interactions between internal and external factors (i.e., dependent differentiation).
See Differentiation (embryology), Epigenesis, Self-differentiation