ECONOMIC BIOLOGY 395 



600 to 900 feet below the surface. Later they rise into the upper layers of 

 water and slowly move northward. Reaching the latitude of Bermuda, a 

 separation occurs. The larvae of the European species move eastward on 

 the long journey back to their native shores, while their tiny American 

 relatives turn toward the coast line of America. 



During their first summer of life the European larvae are found in the 

 western Atlantic. By the second summer they have reached the central 

 Atlantic, and by the third they have arrived off the coastal banks of Eu- 

 rope. During their two and one-half years in the ocean, they have attained 

 a length of from two to three and one-half inches, but still retain their flat, 

 leaf-like larval form. They are now faced with a new way of life and must 

 be prepared to meet it. In the course of the autumn and winter a meta- 

 morphosis takes place. They cease feeding, lose their larval teeth, shrink 

 in depth and length, and become elvers or little eels. While they are shaped 

 like their parents in miniature, they are still transparent, and so are known 

 as "glass eels." 



Our American eel has a shorter larval history. Here again the timing is 

 perfect, for it reaches its home shores and the elver stage of existence in 

 about one year. 



After the transformation from larva to elver, the females of both species 

 ascend the fresh-water streams of their native land to live their lives in the 

 interior until the moment when the migratory instinct drives them back 

 to the sea. In these journeys upstream they use pipe lines and sewers and 

 clamber over falls and surmount dams to reach their destination. The males 

 however, remain in the brackish waters of lagoons and estuaries, where 

 they grow to maturity, and await the downstream migration of the fe- 

 males. 



As eels have been found in ponds having no outlets or inlets, it is be- 

 lieved they will travel overland to reach these oases, choosing nights when 

 the grass is damp for the journey. As there is no evidence to establish this 

 presumption, their presence in these isolated waters is still something of a 

 mystery. They are also at home in high as well as low altitudes, having 

 been found in Swiss lakes 3000 feet above sea level. 



All eels in the headwaters of large streams are found to be females. As 

 a rule they lie buried by day in the muddy bottoms where there is still- 

 water, and venture to feed abroad at night. Being scavengers and omniv- 

 orous, they will eat almost any available food, either living or dead. They 

 have even been known to eat their own kind. 



Female eels average from two to three and one-half feet in length, but 

 have been known to reach four feet and weigh as much as sixteen and one- 

 half pounds. A4ales average around fourteen to eighteen inches in length, 

 but never grow larger than two feet. The vertebrae of these fish mark the 

 only difference between the American and European species; the former 

 have an average of 107 segments, while the latter averages 1 14. 



