1894.] Zoology. 269 
ZOOLOGY. 
The Irritability of Noctiluca.—M. Jean Massart has been 
conducting a series of experiments to ascertain to what stimulants the 
Noctilucæ respond, as shown by their phosphorescence, and to what 
extent the phosphorescence is modified by exterior agencies. The au- 
thor finds that these organisms are sensitive (1) to a slight agitation of 
the water, (2) to sudden variations in the temperature and density of 
the water, and (3) to a great number of chemical substances. As to 
the first stimulant mentioned, the author discovered, by an ingenious 
experiment, that the agitation of the water produces a deformation of 
the body of the Noctiluca, and it is this deformation which causes the 
phosphorescence, and not a vibration transferred to the animal from the 
water in motion. The experiments testing the effect of certain volatile 
substances upon the organisms are exceedingly interesting. Amyline 
produces hyperesthesia, the light is more intense than in normal indi- 
viduals. This condition lasts for five minutes, then all is dark. At a 
slight blow on the vessel the phosphorescence reappears, showing that 
sensibility has not been lost. Bromoform acts as an anesthetic. For 
about five minutes the Noctiluca subjected to its influence emit a feeble 
light which slowly fades out. At the end of twenty-five minutes the 
light-is almost imperceptible ; anesthesia persists. After twenty hours 
the normal state is recovered. The effect of acetone is similar, but 
more rapid in action. At the end of five minutes the phosphorescence 
disappears entirely, and at the end of twenty-eight minutes a slight 
tap on the vessel causes a diffused light, which persists for some seconds 
showing a return to the normal state. 
Some substances produce anesthesia immediately, without any dis- 
play of irritability (alcohol, methyl and paraldehyde) ; others result in 
the death of the organism without any luminous reaction (piperidine). 
lorhydrate of morphine and metaphosphate of sodium appear to 
ave no effect upon the Noctiluca, which is astonishing since the latter 
sudstance is considered an energetic coagulant of the albuminoids. 
While a slight agitation of the water containing Noctiluca increases 
the phosphorescent light, a violent shaking destroys it: This the au- 
thor believes, is due to a blunting of the sensibility of the organism to 
the shock. A few minutes in quiet and darkness restores the animal 
to its normal irritability. 
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