Specific Gravity and Luminescence in Noctiluca, etc. 253 



11. Noctilucas injured by puncturing with a needle or by a strong 

 induced current respond to mechanical or electrical stimulation. If 

 completely broken to pieces by pressing through cheese-cloth, the 

 filtrate gives a constant glow, but there is no flashing on stimulation. 



12. The luminescence is traceable to points of light coming from 

 granules (photogenin) in the protoplasm. No photophelein could be 

 demonstrated. 



13. Noctilucas may be anesthetized by m/8 ether, 1/3 saturated 

 chloroform, 1/16 saturated thymol, 1/8 saturated chloretone, m ethyl 

 and m/8 butyl alcohol, so that they fail to give a flash on stimulation, 

 but they always give a very faint glow; this disappears and the normal 

 response returns on removing the anesthetic. Light-production is 

 dependent on the consumption of oxygen. Whether the anesthesia 

 of luminous cells is due to the fact that oxygen can not pass through 

 the membrane, or to the fact that it can not be used, was tested by an 

 experiment in which the cell-substance of anesthetized cells was per- 

 mitted to come into contact with dissolved oxygen. Narcotized cells 

 were broken up by shaking with sand and it was found that they pro- 

 duced only a faint light, whereas normal cells so treated became very 

 briUiant. The anesthetic must therefore attack the mechanism of the 

 utilization of oxygen in the cell, and not the permeability of the cell- 

 membrane for oxygen. 



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