John Rogerson Cotter and Peter Chalmers Mitchell

“ The luminous organs appear to be specialized skin lands which secrete a fluid that becomes luminous on slow oxidation. The essential part of the organ remains a collection of gland cells, but in the more complex types there are blood vessels and nerves, a protecting membrane, an iris-like diaphragm, a reflector and lens. As the distribution and probably the colour of the light varies with the species, these organs may serve as recognition marks. ”

“ It has been shown, however, that a previous exposure to light is always necessary. Sir James Dewar found that if ammonium platinocyanide, Balmain's paint and some other substances are cooled to the temperature of liquid air and exposed to light, they do not phosphoresce, but as soon as they are allowed to warm up to the ordinary temperature they emit a brilliant light. On the other hand, some bodies, such as gelatin, celluloid, paraffin and ivory, are phosphorescent at very low temperatures, but lose the property at ordinary temperatures. ”

“ Closely allied to this form of luminescence is crystalloluminescence, a phosphorescent light seen when some substances crystallize from solution or after fusion. This property is exhibited by arsenious acid when crystallizing from solution in hydrochloric acid.
Chemiluminescence is the name given to those cases in which chemical action produces light without any great rise of temperature. Phosphorus exposed to moist air in a dark room shines with a soft light due to slow oxidation. Decaying wood and other vegetable substances often exhibit the same property. ”

“ The organs consist of a pale transparent superficial layer which gives the light, and a deeper layer which may act as a reflector. They are in close connexion with the tracheae and the light is produced by the oxidation of a substance formed under the influence of the nervous system, and probably some kind of organic fat In the females the phosphorescence is probably a sexual lure; in the males its function is unknown. ”

“ The so-called lantern flies are Homoptera allied to the Cicadas, and the supposed luminous organ is a huge projection of the front of the head, regarding the luminosity of which there is some doubt. The glow-worms and true fire-flies are beetles. Eggs, larvae and adults are in some cases luminous. ”

“ Lenard (Wied. Ann., 1889, xxxviii. 90) , have shown that the phosphorescence of calcium sulphide and other phosphori depends on the presence of minute quantities of other substances, such as copper, bismuth and manganese. The maximum intensity of phosphorescent light is obtained when a certain definite proportion of the impurity is present, and the intensity is diminished if this proportion is increased. ”

“ One of these disks is close to one end of the drum, the other to the opposite end, and the sectors are so arranged that, when the disks are made to rotate, the hole in one end is open while that in the other is closed, and vice versa. If the eye be placed near one hole, and a ray of sunlight be admitted by the other, it is obvious that while the sun shines on an object inside the drum the aperture next the eye is closed, and vice versa. ”

“ The deep-sea Decapod Crustaceans belonging to many families are luminous. A. Alcock observed that in some of the deep-sea prawns a luminous secretion was discharged at the bases of the antennae, but in most cases the luminous organs are numerous eye-like structures on the limbs and body. ”