92 
substances (les substances chromogeniques ) concerned in these changes 
consist of a definite, crystallizable substance, the ehromogen proper, 
which has been described by Letellier ( 268 ) (see footnote to Dubois’s 
article), and a ferment. To the former Dubois gave the name 
“ purpurin," and to the latter “purpurase.” Xo special evidence has 
been brought forward by Dubois, or by anyone else for that matter, 
to indicate that purpurase is an oxidizing ferment. Indeed, its con- 
duct toward the ordinary oxidase reagents seems never to have been 
investigated. However, the changes resulting in the production of 
the pigment in the pigment gland of Mu rex brandaris , in which it 
evidently participates, present many close analogies to those oxida- 
tions which are accomplished by oxidases, and hence certain authors 
have been led to put purpurase in the class of oxidizing ferments. 
LUCIFEEASE. 
The production of light by animals and plants has been the subject 
of many researches. In this connection it was long ago pointed out 
by Dubois ( 145 -- 14T ) that the active agent of light production in animals 
and plants is a substance having the general properties of a ferment. 
This enzyme he has called “ lucif erase." According to Dubois ( 146 ), 
the transformation resulting in the production of light in animals and 
plants takes place under the influence of life, water, and a suitable 
temperature. From his earlier researches on the subject he con- 
cluded that physiological fight is not the result of a combustion, nor 
even of a slow oxidation, but a direct chemical act (mais directe). In 
his later investigations, however, he claims to have shown that the 
fixation of oxygen is necessary, the oxidation taking place not directly 
but indirectly, and for the most part, at least, through the action of 
luciferase as an intermediary, which thus conducts itself like an 
oxidizing ferment. In tins connection he observed that the luminous 
organs of the Lampyridse and also the eggs contained in the ovaries 
of the females give a beautiful blue color with tincture of guaiacum. 
So, also, the filtered extract of the luminous mucus from the body of a 
dead fish, prepared with chloroform water, gave a similar reaction. 
Dubois ( 147 ) concludes, therefore, that the photogenic substances con- 
cerned in the production of physiological fight are “lueiferin” and 
‘‘luciferase.” In other words, the light generated by various life 
forms is the result of a chemical change, probably an oxidation, 
brought about by the action of luciferase on luciferin. My own 
experience with the firefly native to the Central and Middle Western 
States, Luciola pennsylvanica, is that the aqueous extracts of the 
luminous organs do not show the guaiacum reaction directly, but 
only after the addition of hydrogen peroxide. The whole subject 
requires further investigation. 
