* 
94 ZOOLOGY. 
body being brought to bear in its stroke. The fins on the back are 
called dorsal fins (fig. 70, d, first dorsal ; d?, second dorsal), and that behind 
: di the anus, the anal fin (a, 
fig. 70). Fishes differ 
from all other vertebrate 
animals in having sets 
of bones not connected 
with the backbone or 
the internal skeleton. 
These bones support the 
oS vertical fins, and are 
Fig. 70.—Skeleton of a Fish. thickest at the skin, 
from which they pene- 
trate towards the vertebre. Fishes consume little air in respiration, and 
are cold-blooded animals, having in general a temperature little above that 
of the water in which they live. 
The mouth of fishes is their only organ of prehension. In some 
it is extremely small, in others extremely large; in some destitute of 
teeth, in others furnished with a multitude of very minute teeth, in 
others, again, with a great number of large and strong teeth, In 
some, as lampreys, it forms a sucker, by which the fish can both affix, 
itself and suck up the blood of the animal on which it preys. The 
teeth of fishes are more various in number, form, and position than those 
of any other animals. Some fishes feed on vegetable food, such as the 
leaves of water-plants ; but most of them feed on animal food, of which 
there is no kind that does not seem to be particularly agreeable to some of 
them.—Fishes are generally oviparous, and the multitude of their eggs is 
prodigious, as may be seen in the roe of a herring or a cod; a few kinds 
are ovoviviparous, the eggs being hatched within the body of the parent, 
and the young produced in a living state——Fishes are generally covered 
with scales, which are variously formed and arranged. Some kinds have 
large bony plates instead of scales—Of the uses of fishes to man, by far 
the most important is that of supplying him with food. It is impossible 
here to enumerate the fishes highly valuable in this respect. Some of 
them are to be found inhabiting both salt and fresh waters, in all 
parts of the world. The herring, cod, and salmon are, however, the three 
species of highest economical importance. 
Fishes are divided into two great sections or sub-classes—OssEous? 
FisHEs, which have hard bones, and Cartinaginous FisuEs, of which 
the bones are cartilaginous, and destitute of true bony fibres. The 
Osseous Fishes are far more numerous than the Cartilaginous ; the 

1 From Latin ovwm, an egg, and viviparus, bringing forth its young alive, 
2 Bony, from Latin os, a bone. 

