Bilateral symmetry in morphogenesis of embryos.

It is suggested that differentiated embryonic cells have a high specificity of molecular constitution as regards the surface layers surrounding their cellular membranes. Correspondingly, specific interface energies may characterize the early contacts between different cell types. The question is raised whether the morphology of the developing embryo may be understood in terms of cellular arrangements which minimize the total interface energy. Bilateral symmetry prevalent in early embryonic development of higher animals might be understood on the basis of the adoption of such a minimum energy principle if, in addition, one assumes that embryonic development is uniquely determined for a particular species.