18 THE UNIVERSE. 



regions of the ocean, abound equally in the muddy waters 

 of our rivers and ponds, and without being aware of it we 

 daily swallow myriads of them in the fluids we drink. If, 

 with the aid of the microscope, we were to scrutinize every- 

 thing that a single drop of water sometimes contains, there 

 would be seen enough to frighten many people. 



Every one who has sailed at night upon the sea, or passed 

 along its shores, is acquainted with the phenomenon of phos- 

 phorescence, which for a long time puzzled the sagacity of 

 the learned. It was .attributed to very different causes, but 

 is now known to depend upon the presence of a multitude 

 of animals. Sometimes, when of small extent, it is caused 

 by fish traversing the w r aves like a flaming arrow ; at other 

 times it is owing to the presence of Medusae, the brilliant 

 discs of which are seen calm and motionless in the depths of 

 the waters ; or to the Physophora, trailing behind them 

 their tresses all spangled with stars like those of Berenice 

 in the firmament. Certain molluscs too, though enveloped 

 in their shells, are nevertheless phosphorescent. Even Pliny 

 remarked that the mouths of persons who had eaten Pho- 

 lades were quite luminous. 



This phenomenon, however, is most frequently seen in 

 places where the sea is in movement ; every wave then 

 rolls with luminous foam against the prow of the ship, and 

 the billows gleam like the starry sky. These myriads of 

 phosphorescent particles, which make the sea sparkle, are 

 only Microzoa of extreme minuteness, but of which the size 

 is increased a hundred-fold by their splendor. 



The ocean produces these animalcules in almost every 

 part. Each bed of it, says Humboldt, is peopled with 



