416 Miscellaneous. 
afforded by Orya barbarica, in which the luminous substance is 
secreted by special organs and can be collected in a state of purity. 
This substance is formed in pyriform, unicellular, hypodermic 
glands, measuring from eight to ten hundredths of a millimetre in 
length and from five to six in breadth. In sections one hundredth 
of a millimetre thick, stained with methylene blue or hematoxylin, 
there can be distinguished in the granular protoplasm of the gland 
numerous rounded or ovoid droplets, which are met with again in 
the excreted matter. These droplets, which have been considered 
by observers in the ease of other luminous animals to be of a fatty 
nature, do not turn black when treated with osmic acid, and exhibit 
the histo-chemical characters of protoplasm or of condensed albu- 
minoids. Immediately after their contact with the atmosphere a 
very refringent spot is observed to arise at their centre; they then 
possess the form which caused me to bestow on these little bodies, 
which are found in all luminous organs, the name ‘ vacuolides.” 
This refringent point becomes the centre of a crystal, or, rather, of 
a group of crystals. The protoplasmic matter excreted thus passes 
from the colloidal to the crystalloidal condition under the eyes of 
the observer, while the light is produced. After a certain time the 
preparation is entirely filled with magnificent groups of crystals in 
the shape of ferns, or arranged in long fasciculate prismatic needies. 
Contact with the air is necessary and stimulates the luminosity, 
but contact with water is no less essential. 
This is due to the fact that the phenomenon is not merely one of 
oxidation, for if the matter be rubbed between the fingers or dried 
the light speedily disappears ; but the substance is capable of re- 
gaining all its brilliancy on being moistened with a little water. 
Moreover the excretory product is distinctly acid, which confirms 
the inaccuracy of Radzizewski’s hypothesis, which sought to explain 
animal photogeny as being due to a slow oxidation in an alkaline 
medium. 
Oxygen permits the respiration of the protoplasmic corpuscles 
passing from the colloidal to the crystalloidal condition, that is to 
say, from life to death. This respiration is really active only in 
protoplasm suitably hydrated, and water is necessary in order that 
the crystallization may take place under conditions favourable for 
the emission of light. The oxygen serves to produce the crystalli- 
zable substance with the assistance of water, and the water enables 
the photogenous crystallization to take place. 
It was these two successive conditions of the photogenous matter 
that formerly led me to believe that there were two distinct sub- 
stances reacting one upon the other. 
In reality there are only two successive stages of one and the 
same substance, which is modified by oxygen and water, and for 
which I shall retain the name luciferin until it has been possible to 
determine its atomic structure.—Comptes Mendus, t. exvii. no. 3 
(July 17, 1893), pp. 184-186. 
