XII. _Chordata_ _Adelochorda_ (Balanoglossus) _Balanoglossus_, _Ptychodera_, _Glossobalanus_ _Urochorda_ (Ascidians) _Larvacea_ _Appendicularia?_ _Thaliacea_ _Salpa_, _Doliolum?_ _Ascidiacea_ _Pyrosoma_, _Phallusia_ Acrania (Amphioxus) Cyclostomata (Cylostomes) _Pisces_ (Fishes) _Elasmobranchii_ _Centroscyllium_, _Spinax_, _Paracentroscyllium_, _Isistius_, _Læmargus_, _Euproctomicrus_, _Benthobatis?_ Holocephalii Dipnoi _Teleostomi_ _Stomias_, _Chauliodus_, _Melanostomius_, _Pachystomias_, _Bathophilus_, _Dactylostomius_, _Malacosteus_, _Astronesthes_, _Ophozstomias_, _Idiacanthus_, _Bathylychnus_, _Macrostomius_, _Gonostoma_, _Cyclothone_, _Photichthys_, _Vinciguerria_, _Ichthyococcus_, _Lychnopoles_, _Diplophos_, _Triplophos_, _Valenciennellus_, _Maurolicus_, _Argyropelecus_, _Sternoptyx_, _Polyipnus_, _Ipnops? Neoscopelus_, _Myctophum_, _Halosausus_, _Xenodermichthys? Macrurus? Photoblepharon_, _Anomalops_, _Porichthys_, _Leuciocornus_, _Mixonus? Bassozetus? Oneirodes_, _Ceratias_, _Gigantactis_, _Chaunax_, _Malthopsis_, _Halicmetus_, _Monocentris_, _Lamprogrammus._ Amphibia (Frogs, Toads, Salamanders) Reptilia (Snakes, Lizards, Turtles) Aves (Birds) Mammalia (Mammals) The only groups of the plant kingdom which are known to produce light are some of the bacteria and some of the fungi and the dinoflagellates (_Peridineæ_) if one is to include them among the plants. Many different species of phosphorescent bacteria have been described, differing in cultural characteristics and structural peculiarities and grouped in the genera, _Bacterium_, _Photobacterium_, _Bacillus_, _Microspira_, _Pseudomonas_, _Micrococcus_, and _Vibrio_. Specific names indicating their light-producing power such as _phosphorescens_, _phosphoreum_, _luminosum_, _lucifera_, etc., have been applied. All the fungi which are definitely known to produce light belong to the _Basidiomycetes_, the largest and most highly developed of the true fungi. Either the mycelium alone or the fruiting body alone, or both, may be luminescent. Among animals the best known forms are the dinoflagellates; _Noctiluca_; hydroids; jelly-fish; ctenophores; sea pens; _Chætopterus_ and other marine worms; earthworms; brittle stars; various crustaceans; myriapods; fireflies and glowworms, the larvæ of fireflies; _Pholas dactylus_ and _Phyllirrhoë bucephala_, both molluscs; squid; _Pyrosoma_, a colonial ascidian; and fishes.