Gilbert Gottlieb's formative role in establishing a science of experimental behavioral embryology is described. His experimental program on the development of species identification served as a model for developmental psychobiologists seeking alternatives to the nature-nurture dichotomies prevalent in the 20th century. Two of the major concepts included in his theory of probabilistic epigenesis, the bidirectional nature of structure-function relationships and the developmental manifold, had profound effects on developmental science during the second half of the 20th century. The recent rise of developmental systems theory as an integrated view of development, heredity, and evolution owes much to Gottlieb's sustained experimental and theoretical work in this broad domain.