168 THE HAUNTS OF LIFE 
like many other animals, probably die after 
the eggs are safely deposited, for none of 
them ever reappear at the coasts or in the 
rivers after spawning. 
There are only a few species of eel which 
enter fresh water; the great majority of the 
family spend their whole lives in the sea, 
many of them in deep water. Moreover, 
some individuals, even of the common eel, do 
not enter the rivers, but probably remain 
about the estuaries till it is time to return to 
deeper water. 
On the other hand, some yellow eels do not 
return to the sea. They may have settled 
down in ponds which they found it easy to 
reach when they were little elvers, but dif- 
ficult to escape from later, or they may lack 
the impulse to migrate. Such eels may live 
a long time and grow to a great size, but they 
never produce eggs. 
All these facts justify the conclusion that 
the common eel is descended from ancestors 
which were entirely sea-fish, and that it has 
taken to a fresh-water life. Whether it will 
go farther in the same direction, we have no 
means of knowing. 
We have followed this story at some length, 
