Within the depth-psychology corpus, ontogenesis occupies a distinctly contested theoretical space, functioning simultaneously as a biological concept, a philosophical operator, and a methodological framework. Simondon provides the most sustained and rigorous treatment, insisting that ontogenesis must be understood not merely as embryological development but as the very process by which individuation constitutes being: to study the individual is already too late unless one has first grasped the ontogenetic operation that brings it forth. For Simondon, ontogenesis names the unfolding resolution of a pre-individual metastable tension, encompassing physical, vital, psychical, and collective registers. The study of ontogenesis must, he argues, precede both logic and ontology. Neumann approaches ontogenesis through its classical pairing with phylogenesis, reading individual psychological development as a recapitulation of the evolutionary history of consciousness — a methodological premise that grounds his entire comparative mythology project. Schore invokes ontogenesis in its strictly neurodevelopmental register, tracking how sensory-modal shifts in early infancy produce concrete changes in ontogenetic adaptations of the maturing organism. Jung mentions the ontogenesis-phylogenesis dyad indexically, as an organizing background assumption rather than a theorized object. Thompson engages the term within the biology of autopoiesis and developmental systems theory. The central tension across these voices is whether ontogenesis designates a closed developmental program or an open, creative individuation that exceeds any pre-given form.