228 FOOT-NOTES TO EVOLUTION. 



The coral reef is the metropolis of the fish. The 

 deep sea, the arctic sea, and the isolated rivers — these 

 are the ichthyological backwoods. 



An exception to the general rule in regard to the 



numbers of vertebrae is found in the case of the eel. 



^ . . , Eels inhabit nearly all seas, and every- 



Origin of eels. u ^u u <. u t^u 



where they have many vertebrae. The 



eels of the tropics are at once more specialized and more 

 degraded. They are better eels than those of northern 

 regions, but, as the eel is a degraded type, they have 

 gone further in the loss of structures in which this de- 

 generation consists. 



It is not well to push this analogy too far, but per- 

 haps we can find in the comparison of the tropics and 

 the cities some suggestion as to the development of 

 the eel. 



In the city there is always a class which follows in 

 no degree the general line of development. Its mem- 

 bers are specialized in a wholly different way. By this 

 means they take to themselves a field which others have 

 neglected, making up in low cunning what they lack in 

 humanity or intelligence. 



Thus, among the fishes, we have in the regions of 

 closest competition this degenerate and non-fishlike 

 type, lurking in holes among the rocks, or creeping in 

 the sand ; thieves and scavengers among fishes. The 

 eels thus fill a place otherwise left unfilled. In their 

 way they are perfectly adapted to the lives they lead. 

 A multiplicity of vertebral joints is useless to the typical 

 fish, but to the eel, strength and suppleness are every- 

 thing. No armature of fin or scale or bone is so de- 

 sirable as its power of escaping through the smallest 

 opening. 



