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, hj^podermic 

 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 hsematoxylin, 

 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 case of other luminous animals to be of a fatty 

 nature, do not turn black when treated with osmie 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 needles. 



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 hicifenn until it has been possible to 

 determine its atomic structure. — Gomptes Bendus, t. cxvii. no. 3 

 (July 17, 1893), pp. 184-186. 



