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 €ffect 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 rhaking 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 for 
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 to 
shine by their own light. Of the most remarkable of the molluscs 
met with are several species of Pyrosoma, which present the 
