142 DIVISION I. VERTEBRAL ANIMALS.—CLASS IV. PISCES. 
CLASS IV. PISCES. THE FISHES. 
Wer now come to the consideration of the most numerous class of verte- 
brate animals, which, in multitudinous variety, fills the ocean-world with 
life, and the inland lakes and rivers with the perpetual spectacle of a joyous 
existence. They inhabit all depths of the ocean (at least as far below the 
surface as animal life is possible), the different genera occupying different 
strata; and many of them are confined by geographical limits, although 
some, and those generally the most useful to man, range through all oceans, 
and appear to be at home in all seas. Many of them are interesting from 
their extreme beauty and gorgeous colors, and others from their great utility 
to mankind as articles of food. The most brilliant tribes inhabit the milder 
regions of the globe, and flash their splendors among the coral-groves of the 
tropical seas. All the colors of the rainbow are combined in the hues of 
their scaly vesture; and as they dart from branch to branch among the 
reefs of coral, through the clear and silvery water, each movement reveals 
new combinations of tints which no art can ever equal. 
There are over eight thousand species of fishes recorded by naturalists, 
and probably there are thousands more in those distant seas which have 
never yet been visited by civilized man. The fecundity of this class is 
extraordinary. A single cod produces, each year, over nine millions of eggs, 
and a sturgeon more than seven, while most of the other species are propor- 
tionally prolific. And yet, preying upon each other as they do, and exposed 
to numerous enemies besides, among whom is man, who destroys countless 
millions annually, were it not for this remarkable increase, the sea would . 
soon be without inhabitants. 
The age of a fish may be ascertained by an examination of the scales, 
which consist of concentric circles, the number of circles corresponding to 
the number of years it has lived. Where seales are wanting, the age may 
be determined by the number of rings on the articulating surfaces of the 
back bone. The life of a fish is a constant struggle for existence, and the 
ocean is the scene of perpetual warfare ; and, consequently, it is not proba- 
ble that many live out the full term of existence. “But, if only few fishes 
die a natural death, a life of liberty makes them some amends for their vio- 
lent end. The tortured cart-horse and ox would, if they could reflect, 
willingly exchange their hard lot and joyless existence for the free life of 
the independent fish, which, from the greater simplicity of its structure, its 
want of higher sensibilities, and the more equal temperature of the element 
in which it lives, remains unmolested by many of the diseases to which the 
warm-blooded, and particularly the domestic, animals are subject.” 
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