IX. 



THE PELAGIC FAUNA AND FLORA. 



The pelagic fauna is made up of very distinct factors. It 

 contains many animals which pass their whole life as wanderers 

 on or near the surface, — probably within a couple of hundred 

 fathoms, — where they drift helj)lessly at the mercy of the 

 winds and waves and currents. While there are stretches 

 of the sea along the line of currents, as, for instance, the 

 course of the Gulf Stream, where the pelagic fauna is more 

 abundant than in other marine regions, there seems to be 

 no portion of the sea from which it is totally absent. The 

 pelagic fauna proper includes representatives of all classes of 

 the animal kingdom, though usually these are of smaller size 

 than their allies on or near the continental shores and beaches. 

 The majority of them are noted for the greater or less trans- 

 parency of their bodies, while their coloring is generally har- 

 monious with that of the surrounding sea. Pale, bluish, and 

 translucent colors characterize the majority of the pelagic ani- 

 mals that live during the day upon the surface of the water. 

 Such are, for instance, the violet or blue tints of the ti-anspar- 

 ent acalephs and siphonophores ; those of the Janthina, which 

 its name describes, of the glassy heteropods and pteropods, and 

 of the iridescent ctenophores, which seem, when touched by the 

 sun, like rainbow frao-ments floatino; in the water. 



The brilliant Sapphirina, the red Daphnia and globigerina, 

 the pinkish or bluish Salpa, are often seen in such masses that 

 they discolor the water for miles, and make the ocean like a sea 

 of milk. By daylight, only the practised eye detects the sep- 

 arate forms which, from their number and delicate texture, melt 

 into each other. But at nio-ht the scene chano-es. The jrreater 

 number of the pelagic animals are brilliantly phosphorescent ; 



