The Chemistry of Light-Production in Luminous Organisms. 193 



tannic and phosphotungstic acids, the light returns after first disap- 

 pearing, even without diluting. 



20. HCl between n/2000 and n/4000 and NaOH between n/250 and 

 n/500 extinguish the light, and the effect is reversible upon neutrali- 

 zation. It can be shown that both HCl and NaOH affect the photo- 

 genin more readily than the photophelein and that the effect of NaOH 

 especially is more readily reversible. 



21. KCN does not inhibit Ught-production even in strong concen- 

 tration. 



22. Saturation with (NH4)2S04, NaCl, or cane-sugar extinguishes 

 the light most readily in the order named, and the effect is reversible 

 except in case of (NH4)2S04 (due to acidity). 



23. In the natural secretion of Cypridina or in the whole animal 

 there is always enough photogenin to completely use up the photo- 

 phelein. The photogenin from one animal will use up a large addi- 

 tional amount (at least 100 times the concentration in one animal) of 

 photophelein, but not an indefinite amount, so that photogenin is not 

 a true enzyme in the strict sense of the word, unless it be an enzyme 

 poisoned by its own reaction products. The photogenin-photophelein 

 system resembles the zymase-cozymase system to a remarkable degree, 

 but it is best for the present to regard photogenin not as an enzyme but 

 only as a substance auto-oxidizable only in presence of photophelein. 



STUDIES ON FIREFLIES. 



DESICCATION AND EXTRACTION WITH FAT SOLVENTS. 



The experiments recorded herein have been made during a period of 

 two years on several different species of firefly — the American Photuris 

 pennsylvanica and Photinus pyralis, the Japanese Luciola vitticollis and 

 L. parva, and the West Indian "cucullo," Pyrophorus noctilucus and 

 P. havaniensis. All the species are essentially similar in behavior, and 

 in general the statements apply to all. 



Contrary to the condition in Cypridina, the photogenic substance is 

 burnt within the cell which forms it and is found there in the form of 

 granules scattered through the cytoplasm. The histological struc- 

 ture of the luminous tissue has been well described by many observers 

 [Townsend (is), Lund (3), Dahlgren (19), Vogel (43), Bongardt (44), 

 Geipel (45), Williams (46)] and need not be considered here. 



The old observation that firefly luminous tissue can be dried and 

 ground up and will phosphoresce when water containing oxygen is 

 again added, gives a simple chemical method of investigating the nature 

 of the photogenic material. The dried material may be extracted with 

 water-free solvents (since the photogen does not oxidize in absence of 

 water) and extracted material as well as the residue from evaporation 

 of the filtrate may be tested for phosphorescence by adding water. 

 The results indicate that a large number of fat solvents will extract 



