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THE FOURTH CLASS OF VERTEBRATED ANIMALS. 1 
THE FISHES— (PISCES). 
[Fishes are the proper vertebrated inhabitants of the waters ; and they are formed 
and organized for living, moving, and in general finding their food, wholly within this 
element. The nature of their locality necessarily makes their history obscure, because 
human observation extends to only a very limited portion of the waters, and in that 
portion to only a trifling depth ; but when we consider that, exclusive of lakes and 
rivers, the seas occupy full seven-tenths of the earth’s surface, that those seas yield 
food as far down as the rays of the sun can extend their life-giving energy, and that 
there is no obstacle in the water to bar the motions of the fish, we can at once see 
that, of all vertebrated animals, they must be the most numerous, and probably they 
I exceed in numbers the whole of the other three classes of the same grand division of 
animated nature. They inhabit, stratum super stratum, as it were, — one species near 
the surface, another near the bottom, and others, again, range through the intermediate 
j depth. What may be the absolute depth of the ocean waters at which life ceases, and 
j the profound of death and darkness begins, we have no direct means of ascertaining, j 
j It varies, of course, with the latitude, being greater as the rays of the sun are more 
j direct, and less as their obliquity increases ; and it probably also varies with the nature 
I of the bottom. In correspondence with the vast range of pasture which is assigned to 
the Fishes, their productive powers are enormous, — the young produced by one Cod-fish, j 
at a single deposit, being ascertained to be not much less than four millions, while in the I 
. common Flounder they are not fewer than one hundred and fifty thousand. A fertility 
so enormous, as compared with anything we are acquainted with on land, of itself 
shows the importance of the Class, and how well they are adapted for supplying each 
other with food. But, interesting as it is, the space to which we are restricted, forbids 
any disquisition on their physiology; and all that we can accomplish, is to render the 
text of the last edition of Cuvier’s great work, as faithfully in substance, and as briefly 
in expression, as we possibly can. Our own original remarks must necessarily be few; 
and we shall inclose them in brackets, the same as this introductory paragraph, to dis- 
tinguish them from the substantive part of the genuine text of Cuvier, which, in the | 
way of systematic arrangement, has received no improvement, since the science of 
Zoology was deprived of that foremost of its cultivators.] 
Fishes are oviparous Vertebrata, with a double circulation, and respiring through the 
medium of water. For this purpose they have, on each side of the neck, branchiae, or 
gills, consisting of arches of bone attached to the os hyoides, or bone of the tongue ; 
and to these arches the filaments of the gills are attached, generally in a row upon 
each, and having their surfaces covered by a tissue of innumerable blood-vessels. The 
water taken in by the mouth passes through among the filaments of the gills, and 
escapes by the gill- openings towards the rear. In its progress through the filaments 
of the gills, the water imparts to these the oxygen of the air which it contains [and 
receives carbon in return, the same as in the lungs of an air-breathing animal. The 
gills of a fish do not decompose water, so as to derive oxygen from it, but merely sepa- 
u 
