12 THE OCEAN WORLD. 



an oar will often excite their luminosity, and sometimes, after the ebb 

 of tide, the rocks and seaweed of the coast will be found glowing 

 with them. Various other tribes of animals there are which con- 

 tribute to this luminous appearance of the sea. M. Peron thus 

 describes the effect produced by Pyrosoma atlanticum, on his voyage 

 to the Isle of France : " The wind was blowing with great violence, 

 the night was dark, and the vessel was making rapid way, when what 

 appeared to be a vast sheet of phosphorus presented itself floating 

 on the waves, and occupying a great space ahead of the ship. The 

 vessel having passed through this fiery mass, it was discovered that 

 the light was occasioned by organised bodies swimming about in the 

 sea at various depths round the ship. Those which were deepest in 

 the water looked like red-hot balls, while those on the surface 

 resembled cylinders of red-hot iron. Some of the latter were caught : 

 they were found to vary in size from three to seven inches. All the 

 exterior of the creatures bristled with long thick tubercles, shining 

 like so many diamonds, and these seemed to be the principal seat of 

 their luminosity. Inside also there appeared to be a multitude of 

 oblong narrow glands, exhibiting a high degree of phosphoric power. 

 The colour of these animals when in repose is an opal yellow, mixed 

 with green ; but, on the slightest movement, the animal exhibits a spon- 

 taneous contractile power, and assumes a luminous brilliancy, passing 

 through various shades of deep red, orange green, and azure blue." 



The phosphorescence of the sea is a spectacle at once imposing 

 and magnificent. A ship, in plunging through the waves, seems to 

 advance through a sea of bright flame, which is thrown off by the 

 keel like so much lightning. Myriads of phosphorescent creatures 

 float and play on the surface of the waves, so as to form one vast 

 field of fire. In stormy weather the luminous waves roll and break 

 in a silvery foam. Glittering particles, which might be taken fox 

 sparks of living fire, seem to pursue and catch each other lose their 

 hold, and dart after each other anew. From time immemorial, the 

 phosphorescence of the sea has been observed by navigators. The 

 luminous appearance presents itself on the crest of the waves, which 

 in falling scatter it in all directions. It attaches itself to the rudder, 

 and dashes against the bows of the vessel. It plays round the reefs 

 and rocks against which the waves beat, and on silent nights, in the 

 tropics, the effects are truly magical. This phosphorescence is due 

 for the most part to the presence of a multitude of Noctiluca, larval 

 crustacean forms, some few Molluscs and Acalephes, which seem 10 

 shine by their own light. Of the most remarkable of the molluscs 

 met with are several species of Pyrosoma which present the 



