LUMINOUS ANIMALCULE. 253 



experiment was still attached to its sea-weed, and 

 this had not been washed up on the beach, but was 

 growing in its native tide-pool when I plucked it ; 

 it had never been out of water a single minute, and 

 the polypes were in high health and activity both be- 

 fore and after the observation of their luminosity. 



LUMINOUS ANIMALCULE. 



Some weeks afterwards I had an opportunity of 

 becoming acquainted with a minute animal to which 

 a great portion of the luminousness of the sea is 

 attributed. One of my large glass vases of sea-water, 

 I had observed to become suddenly luminous at night 

 on being tapped with the finger ; the light was in 

 minute but brilliant sparks, chiefly at various points 

 on the surface of the water, and around its edge. It 

 is possible, however that the vibration of the glass 

 produced a more powerful effect on the animals in 

 contact with it, than on those in the water at some 

 distance. After the first tap or two, the light was not 

 again produced, and no jarring or shaking of the ves- 

 sel would renew it. I determined to examine the 

 water carefully in the morning. 



In the mean time, however, in the course of 

 examining some polypes from another vessel, I unin- 

 tentionally isolated a minute globule of jelly, which I 

 presently recognized as Noctiluca miliaris. Eemem- 

 bering that this animalcule is highly luminous, I 

 immediately suspected that the luminous points of 

 my large vase might be owing to the presence of this 

 same little creature. I accordingly set the jar in the 



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