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 has 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 hypothesis 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 () 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 () states that while oxygen is a necessary factor to 
light production in the Lampyride, this does not prove that the 
chemical process is an oxidation. 
Jousset de Bellesme (**) 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 (*) noted that 
Lavoisier held a similar view. The nature of the substance con- 
sumed in this biologic oxidation—the Nocttlucin of Phipson (*”) the 
Luciferine of Dubois (7 1% 2°) and the Photogen of Molisch ()—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; Kélliker (7) and Macaire (“) 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 (’).) 
Of the more recent theories, Dubois (*°) states that the photogenic 
material of Pholas dactylus gives some reactions for a nucleo-albumin, 
while Polimanti () regards the luminous secretion of Pyrosoma 
elegans as of a fatty nature; McDermott (°°) is inclined to regard the 
active substance as a lipoid or phosphatid.!. Golodetz (?*) 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 Lampyride and of Phengodes 
laticollis blacken imtensely 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, 
