LIFE OF THE SEA 533 



to the surface to breathe. It cares for its young like other 

 mammals. 



Here, too, are found the jellyfish, the Portuguese man-of- 

 war (Figure 171), some fishes, many crustaceans, a few in- 

 sects, turtles, snakes, and mammals. Most of these animals 

 are lightly built and are well equipped for floating and 

 swimming. Some sea animals, like the oyster, barnacle, 

 and coral polyp, are fixed, and rely upon the currents of 

 the water to bring them their food, while others, like the 

 crab, the lobster, and the fish, move from place 

 to pbce in search of prey. 



In the warmer seas the surface water is often 

 filled with minute microscopical animals which 

 have the power, when disturbed, of emitting 

 light, so that when a boat glides through these 

 waters at night, a trail of sparkling silver, called 

 phosphorescence, seems to follow in the wake. * 



Between the surface and the bottom of the FlGURE 1T1 

 deep ocean there seems to be a vast depth of water almost 

 devoid of life. This region, like the bottom of the ocean, 

 has been little explored and there may be life here which has 

 not been discovered. From the bottom of the sea the 

 dredge has brought up some very curious forms of life. 

 Here under tremendous pressure and in profound darkness 

 have been developed species of carnivorous fishes. 



Some of these have large, peculiarly well-developed eyes 

 and others have not even the rudiments of eyes. As the 

 light of the sun never penetrates to these depths, it would 

 seem at first that eyes could be of no use, but it has been 

 found that some of the animals of the ocean bottom have 

 the power of emitting light in some such way as the glow- 

 worm and firefly do, and it is probable that it is to see 



