Of six holopelagic polychaete families, the Tomopteridae and Alciopidae are the only ones having representatives that appear to be photogenic. Previous investigators localized the site of photogenic organs to certain parapodial glands in the tomopterids. Photogenic organs have not been demonstrated in the alciopids, but some species have been reported with little substantiation to be luminescent. The structure and function of the photogenic organs and the nature of the luminescent products are incompletely known, exemplifying gaps in the knowledge of the anatomy and life history of pelagic polychaetes.