Larvaceans, common members of marine plankton communities, filter-feed with renewable, external, mucous houses. The houses of some species of Oikopleuridae produce endogenous bioluminescent flashes upon mechanical stimulation and may contribute significantly to surface luminescence. To determine which members of the Oikopleuridae are luminescent, we examined several species for stimulable luminescence and for morphological features responsible for or associated with light production. Luminescence is newly reported from house rudiments and from clean, particle-free houses of Oikopleura rufescens and Stegosoma magnum. In these species, light emanates from previously undescribed fluorescent inclusions in the house rudiment. Neither fluorescence nor luminescence were detected from other parts of the body. Both species also possess oral glands, which apparently are not directly involved in light production but serve as a convenient taxonomic marker of luminescence. All six known luminescent species of larvacea...