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PHOTOGENIC ORGANS OF LAMPYRIDS 167 



stances, the first he calls luciferase, resembling an enzyme and 

 resulting from the granular degeneration of bioproteon in the 

 photogenic cells, the second substance he calls luciferine, which 

 he obtained in an impure state (and had not then analyzed) he 

 thinks occurs in the blood throughout the body, and considers 

 it to be non-living material, inasmuch as it can withstand tem- 

 peratures incompatible with life, with the addition of oxygen 

 and water. (Later ('11) Dubois abandoned these two terms, 

 which he states were provisional and which gave rise to disputes 

 of a compromising nature.) As a passageway for the blood 

 carrying the luciferine to the photogenic organ he figures large 

 spaces or cracks in the latter. The existence of such spaces 

 seems improbable, as they do not appear to have been observed 

 by any of the subsequent students. Lund ('11) believes that 

 the spaces are " nothing but the region of the vertical cylinders 

 and tracheae which sometimes do not stain readily." Dubois 

 bases his conclusions largely on the luminous bivalve mollusc, 

 Pholas dactylus L. 



Wielowiejski ('82) thought that the tracheal end-cells in the 

 luminous layer, as well as their tracheal matrix were analagous 

 to the red blood-corpuscles of vertebrates. The oxygen of the 

 air going into the tracheal capillaries would be absorbed and 

 given over to the proper photogenic cell. The nervous system 

 would excite the parenchyma (photogenic) cells to secrete, and 

 photogeny would be a process of simple oxidation. 



Bongardt ('03) repeated the various experiments of Dubois 

 but obtained somewhat different results. He holds that Dubois' 

 experiments were often of too short duration, and perhaps the 

 gases used too impure to give trustworthy results. Bongardt 

 made an extensive study of the physiology and the finer struc- 

 tures of the photogenic organ. He found many nerve processes 

 entering the photogenic layer, following the tracheae, but unlike 

 Owsjannikow, never found nerves penetrating the cells them- 

 selves, although he did find them penetrating the tracheal end- 

 cells. He considers the luminescence in the Lampyridae to be 

 a secondary phenomenon. 



Kuhnt ('07) suggests that possibly the light produced by 

 Lampyridae is bacterial. 



