338 EARTH TRESPASS BBS. 



Eel, indeed, such a structure is absolutely necessary, 

 and that for the same reason which makes it useful in 

 the climbing perch. 



Although the Eels live much in rivers, they find a 

 larger supply of food in ponds and ditches than in 

 rivers; and accordingly, such places are generally 

 well stocked with Eels. For example, not far from 

 my house there is a little^ muddy, narrow ditch, 

 scarcely seven or eight feet wide, running parallel 

 with the Thames, and only divided from it by the 

 river wall. This ditch is a favourite resort for Eels, 

 which find their way into it through the channels by 

 which the ditch communicates with the river ; and, 

 being there, prefer their new quarters. 



Such fortunate Eels as these would not need to 

 migrate. Being able to exist in salt water as well as 

 in fresh, they do not feel themselves discommoded 

 by the sea water which flows into their ditches every 

 tide. They have plenty of frogs and aquatic inhabit- 

 ants for food ; and, owing to its connection with the 

 river, the ditch never runs dry. 



But it is a different business when the Eel gets 

 'into ponds unconnected with springs, or into ditches 

 that have no communication with rivers. In a time of 

 lengthened drought they are sure to dry up, and then 

 the Eels must perish, unless they could find some way 

 of travelling to the water. Accordingly, the power of 

 existing without water for a time is given to them by 

 the modification of the breathing organs ; while the 

 means of transit is afforded by the sinuous movement 

 of the snake-like body. 



On Cut 1 7, two species of Eel are shown, the upper 



