PHOTOGENIC ORGANS OF LAMPYRIDS 165 



The photogenic organs in fireflies (Lampyridae) and the neo- 

 tropical elaters of the genus Pyrophorus are perhaps the most 

 efficient and highly specialized of all photogenic tissues, and for 

 this reason, as well as because of their general abundance they 

 have for years been the favorite objects of study in this field. 



Forster ('82) advanced the hypothesis that the luminous mate- 

 rial of the Lamypridae was phosphorus dissolved in the animal 

 fluids. He found that the Lampyridae shone more intensely in 

 pure oxygen than in air. 



According to Lindemann ('63), Treviranus explained the lumi- 

 nescence in these insects by stating that the fat-body absorbed 

 phosphorus. Treviranus ('18) says, p. 109: "Der Einfluss des 

 Thiers auf das Leuchten geschieht mittelbar, durch das Athem- 

 holem," and further: "Das Ausstrohmen des Lichts hangt daher 

 von der Wilkuhr des Kafers ab." Treviranus found no nerves 

 going to the luminescent mass. 



Another of the older explanations of the phenomenon of light 

 production, is, according to Lindemann, that held in the begin- 

 ning of the nineteenth century, by Monti, Carradori and Bec- 

 caria, who thought that fireflies were light-absorbers (thus com- 

 parable to certain minerals) in having the power to take in the 

 sunlight, and in the night, to give it out again. 



Michael Faraday ('14) made some interesting observations on 

 the luminescence of the firefly and glow-worm. He was of the 

 opinion that the light "has a dependence on the respiration" 

 . . . . and that the light-giving power seemed to depend 

 "more on the chemical nature of the substance than upon the 

 vital powers of the animal." He found no sensible heat accom- 

 panying this production of light. 



From the middle of the last century, with the advance in 

 chemical and physiological research and the perfection of the 

 microscope, the phosphorus theory was soon abandoned, to be 

 replaced to a large extent by one of the oxidation of an albu- 

 minous substance, and this with some modifications is the gen- 

 eral view of the present day. 



As early as 1857, von Kolliker was able to analyze the two 

 component layers of the photogenic organ, the inner or non- 



