198 The Under-Water World 



such as the loss of teeth and the acquire- 

 ment of a barrel-shaped instead of a leaf- 

 like form. The glass elvers, as they are 

 then called, enter most of the great tidal 

 rivers in immense numbers during their 

 third spring, at which time huge quan- 

 tities are netted for food. At first rely- 

 ing on microscopic food, the growing eels 

 soon acquire a taste for almost anything 

 they can swallow. Fish of all kinds, 

 crayfish, and even water rats and aquatic 

 birds, all find acceptance by a hungry eel. 

 The fish penetrate to the sources of 

 almost every river. Their gill chambers 

 can retain sufficient water to permit 

 them living ashore for long periods, 

 and this combined with great muscular 

 strength helps them to make lengthy 

 trips overland, travelling as far as some 

 of the Swiss lakes, situated several thou- 

 sand feet above sea level. After some 

 years in fresh water the eel returns to 

 its birthplace in the sea, covering the 



