THE PERCH. 301 
on, or preceded by, strong, sharp spines, capable of 
inflicting a severe wound, and forming a very efficient 
weapon of defense, so that the boldest and most vora- 
cious of fishes rarely venture to seize them. All the 
genera have two dorsal fins—the first, or foremost, of 
which is invariably supported on spines, as opposed to 
soft branched rays ; while the second, or hindmost, is of 
soft texture, preceded by one or more hard spines—two 
pectoral fins, both soft-rayed—one ventral, and one anal, 
each of which is often preceded by one or more spines 
—and one caudal; or tail fin, which is the main propell- 
ing power of the animal. On the number of the hard 
spines supplementary to the soft fins, are founded the 
different families; and on the number of spines in the 
first dorsal, the dental system, and some other parts of 
the bony structure, the lesser, or individual distinctions. 
On color, as distinctive of genera, or even varieties, 
little or no reliance can be placed, unless confirmed by 
distinct variations in the bony formation; since in all 
fishes there is observed to exist a great range of hues, 
shades, and even positive colors, arising sometimes from 
mere casual influences operating on individual speci- 
mens, sometimes from accidents of light or shade affcct- 
ing peculiar situations, and most frequently of all fiom 
the soil and character of the feeding-grounds, and from 
the various mineral or earthy substances held in solution 
by the waters they frequent. 
These latter influences frequently modify the same 
