8 
FISHES. 
membrane, more or less transparent, stretched 
over parallel or radiating rays. These rays are 
slender bones, sometimes consisting of a single 
piece, stiff and spinous ; at other times composed 
of several pieces jointed together, and therefore 
flexible ; the latter are frequently divided each 
into two or more branches at the tip. These cha- 
racters of the fin-rays afford a ground for the 
division of one of the Sub-classes into Orders. 
The fins of Fishes are of five kinds, and are 
designated according to their position, as pectoral, 
or breast-fins ; ventral, or belly-fins ; dorsal, or 
back-fins ; anal, or vent-fins ; and caudal, or 
tail-fins. The pectorals and ventrals are arranged 
in pairs, and correspond to the fore and hind 
limbs in other vertebrate animals ; the pectorals, 
for instance, representing the wings of birds, 
the ventrals the feet. The other kinds have 
nothing corresponding to them in the other 
Classes, except it be the web-like expansion of 
skin that fringes the Newts, &c., or the carti- 
laginous dorsal in some of the Cetacea. The dorsal 
runs along the medial line of the back ; it was 
formerly supposed to preserve the body in a per- 
pendicular position in the water, but recent ex- 
periments have shown that it is not necessary for 
that object, though it may be accessory to it. 
Almost all fishes have this fin, and many have 
two ; while a few, as the Haddock and Cod, have 
three dorsals. The anal fin corresponds to the 
dorsal, but is placed beneath the body, just be- 
hind the vent. The caudal is the most important 
fin of all, being the great organ of motion. It is 
the termination of the body, being expanded 
around the posterior extremity. In those fishes 
