FISHES. 
Before speaking of tlie habits of the principal kinds of fishes, it is 
desirable to glance at their organization, and npon the manner in 
which they execute their physiological functions. 
Fishes are intended to live always in water, and this circumstance 
has impressed its seal upon their organization. Nevertheless, then- 
forms are very varied ; they are generally oblong, compressed laterally. 
They have no neck, the head being merely a prolongation of the 
trunk. In the majority of instances, the tody is covered with scales, 
generally a thin bony substance developed out of the skin and over- 
lapping each other, like the tiles of a roof. 
Nothing is more remarkable than the variety and brilliancy of 
colour in fishes ; they present almost every gradation, from golden or 
silver, and other dazzling colours, mingling with shades of blue, green, 
re d, and black. 
Fishes are essentially formed for swimming (Fig. 339), and all their 
Members are adapted for this purpose. The anterior members, which 
correspond with the arms in man and the wings in birds, are attached 
to each side of the trunk, immediately behind the head, and form the 
‘Pectoral fins. The posterior members occupy the lower surface of the 
I’ody, and form the ventral fins. The latter, which arc always over 
the ventral line, may be before, beneath, or behind the former. Fishes 
Possess, besides, fins in odd numbers. The fins which erect themselves 
011 the back are called the back or dorsal fins, those at the end of the 
t a il are the caudal fins ; finally, there is frequently another attached 
t ,J the lower extremity of the body, which is called the anal fin. 
