$0 CLASS IV. ORDER I. 



creased probably from five to ten fold within the 

 last century. Probably the encrease of animal 

 substances, along the river and its tributary 

 branches, which are perpetually washed into it, 

 furnishes an immense addition to the stock of 

 food suited to their natures. 



Most fish feed on both animal and vegetable 

 substances. Some species will live many years 

 in a vessel of mere water. Whether they possess 

 the power of decomposing water and forming new 

 compounds fit for food, or -whether the water ab- 

 sorbs organized matter from the atmosphere suf- 

 ficient to support them, or on what other principle 

 their lives arc prolonged in this situation, is not 

 determined. But the same difficulties present 

 themselves in regard to the leach and numerous 

 other avertebral animals ; excepting that the lat- 

 ter have a less complicated organization. 



ORDER 1. APODES.* 



Gill-membranes (if any} with long rays ; ven- 

 tral fins none. 



ANGUILLA, (eel,) head smooth ; nostrils tubu- 

 lar ; eyes covered by the common skin ; gill-mem- 

 branes 10-rayed ; body roundish, smooth, mu- 

 cous ; dorsal, caudal, and anal fins united ; spi- 

 racles (breathing holes) behind the head or pecto- 

 ral fins. 



MURAENA, (feel, serpent-eel,) body eel-form ; 

 pectoral fins none ; spiracle on each side of the 

 neck. 



* I prefer the orders of Linneus in this class, for reasons given in the 

 preface. Cuvier says the orders of fish are more difficult to define than 

 Ike orders of any other class of animals. 



