CONTRACTILITY AND PHOSPHORESCENCE. 



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nous property is left to the choice of the organism itself. The 

 best way to deal with an organism of this nature is to expose it 

 to the fumes of ammonia, or add a few drops of strong ammonia 

 to the sea-water in which it lives. Even the most obstinate of 

 phosphorescent organisms may be made to reveal their luminous 

 property by this method. Another and perhaps a simpler 



Fig. 2. — Nyctiphcines norvegica. lAiminous organs are shown by dark dots. 



method is to extract the tissue of the suspected organ, and 

 crush it or tease it and expose the contents freely to the air, 

 in the presence of moisture. If the tissue is really photogenic, 

 it will shine when thus separated from the inhibitory control of 

 the organism, and the direct access of oxygen to the tissue is 

 thus artificially made possible. A small and slender phosphor- 



i w Oil 



Fig. 3. — Scopetus Rafiiiesgiiii. (After Liitken.) Luminous organs are shown by dark dots. 



escent earthworm which inhibited the emission of light in a 

 most obstinate way, when gently crushed between two slides 

 and exposed to the air or thrown into water, shone like the 

 filament of an incandescent lamp.^ 



^ The presence of water seems to exercise quite a marked influence upon the 

 luminous oxidation of the substance, although water does not appear to take any 



