Studies of the development of nervous systems in diverse animals are critical for understanding evolution of the nervous system. Although our understanding of neurogenesis in vertebrates and arthropods is quite extensive, a huge gap remains in our knowledge of cellular and molecular mechanisms that govern neurogenesis of a centralized, adult nervous system in a large group of animals, the spiralians. Capitella offers several advantages as a model for neurogenic studies, most notably that its nervous system undergoes both embryonic and adult neurogenesis, and it exhibits robust adult regeneration of its nervous system. We study the cellular origins and cell behaviors of the neuronal precursors of the brain by utilizing a combination of DiI lineage tracking, immunohistochemistry, analysis of cell division patterns, gene expression, and functional genomics. Our studies have revealed some fundamental differences compared with similar processes in insects, but several similarities with non-insect arthropod and vertebrates. More recently, we have extended our studies to include the development of the nervous system in the context of regeneration. We are also investigating sensory systems at distinct life history stages, specifically the relationship between the larval and the adult eye in Capitella.