76 Animal Life by the Sea-shore. 



cause one of the most striking phenomena to be witnessed on a 

 hot summer night — the phosphorescence of the sea. This 

 phosphorescence is caused by many different organisms belong- 

 ing to various divisions, minute jelly-fish and the microscopic 

 crustaceans which form so great a proportion of the surface 

 fauna contributing largely to the phenomenon. On our coasts, 

 however, the luminosity of the sea is due in most cases to an 

 animalcule appropriate!}' termed Nodiluca miliaris, a unicel- 

 lular organism, myriads of which are at times floating at the 

 surface. Nodiluca, which is just large enough to be visible 

 to the naked eye, being one-twenty-fifth of an inch in diameter, 

 is a little gelatinous creature of approximately globular shape ; 

 when seen singly it appears almost colourless, but masses of the 

 animalcule appear of a reddish-brown tint, hence the discolora- 

 tion of the water near the shore which so frequently occurs 

 after a night of magnificent phosphorescence. The cause of the 

 luminosity of these creatures is not known ; the light, however, 

 always shows best when the water containing them is disturbed, 

 as by waves or ripples, the action of a boat, or some animal 

 swimming on the surface. 



