492 RECORD OF SCIENCE FOR 1886. 



tiou, form, and powers of the luiiiiuoiis organs vary slightly in different 

 species, and a few have no such organs. One of the most brilliant is 

 Pyrophorus noctilucus, which has been especially studied by Mr. Du- 

 bois." A preliminary anatomical examination compelled Mr. Dubois to 

 make certain coriectioiis of statements previously current in regard to 

 the situation of the stigmata, the distribution of the tracheae, and the 

 relations of the nervous system to the light producing organs. 



The luminiferous organs are " composed of a special adipose tissue and 

 of certain accessory organs. Histochemical investigation revealed the 

 presence of a body which presents the character of guanin. Intense his- 

 tolysis takes place in the photogenous adipose tissue, the changes being 

 provoked or stimulated by the penetration of blood into the luminous 

 organs; the histolytic process is accompanied by the formation within 

 the photogenic cell of a vast number of small crystalline agglomerations 

 of special optic properties, and especially remarkable for their double 

 refraction." 



The blood, however, is " not indispensable for the production of light, 

 for the ovum is luminous even before segmentation, and the adipose photo- 

 genic cell, when isolated, exhibits the same property: these facts point 

 to a similarity between the substance of the adipose body and that of 

 the vitellus. ^he larvoe, hitherto unknown, have been by the author 

 found to resemble those of other Elateridte, but are luminous. "At 

 first they have but a single luminous organ, but this extends over all 

 the segments, and is localized at the points where histolysis is most 

 active. In the adult insect there are three luminous spots, which are 

 so placed as to aid walking, swimming, and flying in obscurity. The 

 muscles of the luminous organs regulate the supply* of blood to the 

 photogenic organs, and so have an indirect action on the production of 

 light; the nerves act through the muscles; the photoseu si tive reflex 

 action has its seat in the cerebroid ganglia; centrifugal irritation of 

 the ganglia i)roduces the appearance of light, but this is not the case 

 with centripetal stimulation. Eespiration has only an indirect influence 

 on the photogenic function, and this by maintaining the vital conditions 

 of the blood and of the tissues; the nature of the food has no influence 

 on the production of animal light. The cell (the non-segmented ovum, 

 or the adipose cell) ])repares the photogenic principles under the influ- 

 ence of nutrition, but the light is not the direct result of the proper 

 activity of the organized and living anatomical element. When the 

 structure of this anatomical element and its vitality are destroyed, the 

 luminous phenomenon can still be produced by a physico-chemical ac- 

 tion, similar to that which converts glycogen into sugar in the liver. 

 Though the luminous organs of Pyropliorus are the most remarkable 

 known to us, the organic expense is almost insignificant as comjiared 

 with the effect produced ; so, too, the loss of energy is very slight, 

 whereas in artificial light it may be as much as 98 per cent." 



