THE FRESH WATERS 165 



of the room, apparently dead ; however, when 

 returned to the water they swam about 

 apparently none the worse for their excursion." 

 Once settled down in suitable quarters the 

 elvers begin to feed and to grow, and are now 

 known as " yellow eels." Their food consists 

 at first of worms, larvae, and small fishes, but 

 as they grow they become very voracious, and 

 will attack water-voles and water-fowl, and 

 even larger fishes, among which they do serious 

 damage. There is even a case on record of 

 an eel, 5 feet long, which attacked a swan ! 

 The owner saw the swan struggling violently, 

 with its head under water. He went to its 

 assistance and found that its head had been 

 seized by a large eel, which held on so 

 obstinately that it allowed itself to be caught 

 and landed. 



About the third summer of an eel's life in 

 fresh water its scales begin to grow. It is an 

 interesting fact that naturalists can tell the age 

 of an eel, or at least the length of time it has 

 spent in fresh water, by examining its scales 

 under the microscope. Each scale is arranged 

 in little zones or rings studded with tiny, limy 

 knobs, separated by narrow rings of smooth 

 material. "This structure is due to the fact 



