THE CHEMISTRY OF LIGHT PRODUCTION 101 



volves something more than respiration, an oxidation of 

 a very definite and particular kind. 



Since Spallanzani's observation that the luminous 

 material of medusas could be dried, and upon moistening 

 would again give light, many confirmatory observations 

 have been made on other forms. Pyrosoma, Pholas, Phyl- 

 lirrhoe, fireflies, Pyrophorus, copepods, ostracods, pen- 

 natulids, fungi, and bacteria can all be dessicated and 

 the photogenic material preserved for a greater or less 

 time. In a dessicator filled with CaClg, dried luminous 

 bacteria lose, after a few months, their power to give light 

 on being moistened. On the other hand, ostracods and 

 copepods will still luminesce after years of dessication. 

 The luminous material in the latter case appears capable 

 of indefinite preservation, but it is possible that the quick 

 loss of photogenic power with dried luminous bacteria 

 is merely an indication that they contain very little pho- 

 togenic substance and that the dried ostracods would also 

 in time lose their power to luminesce. It is certainly 

 a fact that the amount of luminous material in a single 

 gland cell of an ostracod is vastly greater than that in 

 the same mass of bacterial colony. 



When the dried powdered luminous material of an 

 ostracod is sprinkled over the surface of water, it goes 

 into solution and leaves luminous diffusion and convection 

 trails plainly visible in the water. Many luminous 

 marine forms give off a phosphorescent slime when they 

 are handled, which adheres to the fingers. It is not sur- 

 prising that this luminous matter should have early re- 

 ceived a name. In 1872, Phipson called it noctilucin and 

 described some of its properties, He regarded the lumi- 

 nous matter which can be scraped from dead fish (luminous 



