350 annual, report Smithsonian institution, 1911. 



is associated with the contractility of protoplasm, as a potential 

 property of all protoplasm, whether exhibited or not, and he rather 

 leaves the reader with the impression that he believes that the par- 

 ticles of food materials are actually burned in the living tissues with 

 the production of an incandescent temperature. 



There lias been a good deal of discussion, to and fro, as to whether 

 the chemical processes involved in the production of light by the firefly 

 and analogous forms are really oxidations, and evidence both for and 

 against the oxidation Irypothesis has been offered. At present the 

 great weight of the evidence is that in all cases the fundamental 

 process is an oxidation, though not necessarily the oxidation of the 

 same photogenic substance. Polimanti ( 58 ) has asserted that the 

 luminous process in Pyrosoma elegans can not be an oxidation, and 

 gives several arguments in favor of the nonoxidative nature of the 

 process, one of which is that the light has a greenish tone. In view 

 of the fact that, as mentioned before, a good many chemiluminescent 

 reactions known to be oxidations produce the sensation of green 

 upon the human retina, this argument certainly does not seem to be 

 valid. Lund ( 42 ) states that while oxygen is a necessary factor to 

 light production in the Lampyridse, this does not .prove that the 

 chemical process is an oxidation. 



Joussetde Bellesme ( 33 ) in 1880 stated that he believed the light to be 

 due to the spontaneous combustion of phosphine, liberated by the 

 decomposition of protoplasm, and Sir Humphry Davy ( 8 ) noted that 

 Lavoisier held a similar view. The nature of the substance con- 

 sumed in this biologic oxidation — the Noctilucin of Phipson ( 57 ) the 

 Luciferine of Dubois ( 17 > 18 ' 20 ) and the Photogen of Molisch ( 53 ) — has 

 been variously regarded by different authors. Many seem to have 

 regarded it as a fat or a fat-like substance; Phipson, who apparently 

 isolated and analyzed a culture of photogenic bacteria, concluded 

 that it contained nitrogen; Kolliker ( 37 ) and Macaire ( 43 ) believed it 

 to be an albuminous body. Embryologically, it appears to be an 

 extension of the fat layer in many, though not in all cases. (See 

 Dahlgren and Kepner ( 7 ).) 



Of the more recent theories, Dubois ( 20 ) states that the photogenic 

 material of Pholas dactylus gives some reactions for a nucleo-albumin, 

 while Polimanti ( 58 ) regards the luminous secretion of Pyrosoma 

 elegans as of a fatty nature; McDermott ( 50 ) is inclined to regard the 

 active substance as a lipoid or phosphatide Golodetz ( 26 ) has shown 

 that the blackening of fats by osmic acid is due to the presence of the 

 oleic (or other unsaturated) acid radical; the present interest in this 

 point is that the luminous tissues of the Lampyridse and of Phengodes 

 laticollis blacken intensely on exposure to osmic acid, indicating 



1 However, it must be said that both Dubois (private communication) and the author have failed to 

 extract a photogenic lipoid with the usual lipoid solvents. 



