irritability — a greater necessity for oxygen—die, almost as soon 

 as taken out of the water — and whose flesh, quickly decomposes. 

 While such as frequent the bottom, have a low degree of 

 respiration — great muscular irritability — less necessity for oxygen 

 -*— live long out of water- — and the flesh, not so soon subjected to 

 decomposition. Thus is each, peculiarly adapted to its general 

 abiding place ; for I need scarcely say, it is a mere vulgar error 

 to suppose that fishes breathe water. Their life is sustained by 

 air, as well as our own. The water taken in, either by the 

 mouth, or by an apparatus fitted for the purpose, in passing 

 through the filaments of the gills, imparts to these, the oxygen of 

 the air it contains ,• receiving carbon in return ; precisely like 

 any of what are popularly considered, air-breathing animals. 

 The water, in its passage through the gills, is not decomposed ; 

 but merely the oxygen extracted from the atmospheric air con- 

 tained in the water. Deprive water of this air, and no fish can 

 live ia it. Now as — especially in cold weather— ^the ground fish 

 are partially, and often wholly, buried in sand or mud, their low 

 degree of respiration, is perhaps necessary to existence; as in such 

 a situation they must obtain a more limited supply of air, than in 

 the free and open water : thus, not A'ery remotely, approximating 

 to the hybernating animals of earth. 



I must close these slight remarks on the Ichthyology of 

 Herefordshire, by adverting to one part of the economy of fished, 

 which remaibs unexplained-'— at least satisfactorily — the aii»- 

 bladder. Its office, is usually supposed to be that of enabling the 

 fish to raise or depress itself in the water, at will, by a sudden 

 and voluntary alteration of its own specific gravity. But this 

 may reasonably be doubted ; for at least one fourth of the race 

 are without it. Were this large proportion, condemned to crawl 

 at the bottom, we might have better reason to believe the air- 

 bladder necessary to empower the fish to rise. It is not so, 

 however. Tho cartilagenous tribes, are deprived of it; and wo 

 have a familiar instance, in our two species of mackerel — both, 

 having bony skeletons ; and both possessed of precisely similar 

 habits ; — yet the one has an air-bladder, and the other has not. 



