194< POPULAR HISTORY OF THE AQUARIUM. 



some of the water in a bucket, seen them for a short time 

 illuminate the whole and then disappear." On our own 

 coasts^ this magnificent effect, produced from small causes, 

 has often been witnessed by those who^ during the summer 

 nights, are out at sea. Among the marine animals produ- 

 cing this effect is the beautiful Noctiluca, an excessively 

 minute globular animalcule with a tail setting out from a 

 small indentation, which seems by its jerks to be the organ 

 of locomotion. In the Mediterranean, as well as on our 

 own seas, this creature is seen in myriads, lighting up the 

 waves as they strike against each other or objects in contact 

 with them. 



Spix, the traveller, tried some interesting experiments 

 with sea-water when thus illuminated. He had some of 

 the water placed in buckets, and found that the hand or 

 any other object dipped in the water shone with a phospho- 

 rescent light. "When the water was shaken, the lights 

 seemed to be eliminated like electric sparks. The minute 

 globules, when examined with a microscope, were found to 

 be of various sizes, but all minute, and it does not appear 

 that the whole body of any specimen is illuminated at once, 

 but different parts at different times. It was observed that 

 each one had at one end a small, navel-like opening, within 



