 Although it is common in philosophy to associate sciences with theories, such that the individuation of a science is dependent on a constitutive theory or group of models, it is uncommon to find presentations of developmental biology that make reference to a theory of development (see discussion in Minelli and Pradeu 2014). Instead, we find references to families of approaches (developmental genetics, experimental embryology, cell biology, and  molecular biology)  or catalogues of “key molecular components” (transcription factor families, inducing factor families, cytoskeleton or cell adhesion molecules, and extracellular matrix components). No standard theory or group of models provides theoretical scaffolding in the major textbooks (e.g., Slack 2013; Wolpert et al. 2010; Gilbert 2010). The absence of any reference to a constitutive theory of development or some set of core explanatory models is prima facie puzzling. Three interpretations of this situation are possible: (a) despite the lack of reference to theories, one can reconstruct a theory (or theories) of developmental biology out of the relevant discourse (e.g., multiple allied molecular models); (b) the lack of reference to theories indicates an immaturity in developmental biology because mature sciences always have systematic theories; and, (c) the lack of reference to theories should be taken at face value.