THE FRESH WATERS 167 



has yet identified the eggs with certainty, nor 

 the very youngest forms of the fish. Minute 

 fry are now known, however, which grow into 

 3-inch long transparent larvae, which feed 

 near the surface of the Atlantic by night, and 

 sink deeper through the day. Some of these 

 " Leptocephalids," which had long been a 

 puzzle to naturalists, were kept in an aqua- 

 rium, and their gradual transformation to the 

 elver stage was observed. Then many of 

 them were taken at different times from the 

 sea, and it was learnt that towards the end of 

 summer they begin to undergo a change into 

 the "glass-eel," or "transparent elver" stage. 

 At the same time, apparently, they begin their 

 migration towards the shore. The process of 

 changing goes on for many months, and, dur- 

 ing that time, they do not feed at all, but live 

 on their own substance. The elver is not only 

 quite different in shape from the earlier form, 

 being now a small eel, but it is fully half an 

 inch shorter. 



As to the last chapter, it is supposed that 

 the silver eels from the British Isles go out 

 to the deep waters of the Atlantic and there 

 deposit their eggs, which rise to the surface 

 and float till they hatch. The eels themselves, 



