52 The Production of Light by the 



are now lifted out of the water to the air, the light immediately 

 becomes bright again. This is not due to stimulation of the fish in 

 handhng, because the same amount of stimulation while the organ 

 is under sea-water containing less than the proper amount of oxygen 

 does not increase the intensity of the light. It is interesting to note, 

 in this connection, that strong, interrupted, induced electrical shocks 

 will not cause a luminous organ, dim from insufficiency of oxygen, to 

 glow more brightly. This shows that, for this material at least, the 

 cell is able to absorb all the oxygen available and that electrical stim- 

 ulation can not cause additional oxygen to enter as a result of increased 

 permeability from stimulation. 



Second, if a luminous organ is removed from a fish and laid face 

 down on a piece of glass, the light, as observed through the glass, 

 disappears almost instantly, except about the edges of the organ in 

 contact with air. On lifting from the glass the organ glows brightly 

 over its whole surface. The glass keeps the air away and the light 

 then disappears with extraordinary rapidity. 



Finally, if one makes an extract of the organ by grinding in sea- 

 water with quartz sand and places the extract in a test-tube, the light 

 quickly disappears, except at the surface of the extract in contact 

 with air. Shaking the tube causes its contents to glow throughout. 



In these experiments it is the rapidity with which the oxygen is 

 used up that is astonishing. Similar experiments can be performed 

 with an extract of Cypridma or pennatulids, but oxygen is not con- 

 sumed nearly so rapidly. The situation is exactly as if one had, in 

 sea-water, an emulsion of luminous bacteria, which also use up 

 oxygen with extraordinary activity. The difference between lumi- 

 nous bacteria and extracts of Cypridina lies in this, that the bacteria 

 use oxygen not only for light-production but also for respiration. 

 Large amounts of oxygen are necessary for the latter. The extract 

 of these fish behaves like an emulsion of luminous bacteria and fur- 

 nishes an additional fact in favor of the view that the light is really 

 of symbiotic bacterial origin. 



DESICCATION. 



If the light-organs of Anomalops or Photoblepharon are cut out, 

 carefully freed of adherent sea-water, and placed in a desiccator, 

 they dry to a hard, leathery mass which is powdered only with diffi- 

 culty in a mortar. On adding water, there is no light, or at most 

 a faint light, if the tissue has been dried very rapidly by placing it 

 very near lumps of CaCl2. No doubt a vacuum desiccator would 

 give better results, but certainly there would be no fight after drying 

 to compare with the great intensity before drying. In this respect 

 these fish behave as luminous bacteria, which give light on moisten- 



