PISCES. 
so conveniently at any object with both 
eyes at the same time. The crystalline lens 
in fishes is a complete sphere, and more 
dense than in terrestrial animals, that the 
rays of light coming from the water might 
be sufficiently refracted. As fishes are con- 
tinually exposed to injuries in the uncertain 
element in which they reside, and as they 
are in perpetual danger of becoming a prey 
to the larger ones, it was necessary tliat 
their eyes should never be shut ; and as the 
cornea is sufficiently washed by the element 
they live in, they are not provided with pal- 
pebrae ; but, as in the current itself the eye 
must be exposed to several injuries, tliere 
was a necessity that it should be sufficiently 
defended ; which, in effect, it is, by a firm 
pellucid membrane, seeming to be a conti- 
nuation of the cuticula stretched over it : 
the epidermis is very proper for this pur- 
pose, as being insensible, and destitute of 
vessels, and consequently not liable to ob- 
structions, and thus becoming opaque. In 
the eye of the skate tribe there is a digitated 
curtain which hangs over tlie pupil, and 
which may shut out the light when the ani- 
mal rests, being somewhat similar to the 
tunica adnata of other animals.” 
We now proceed to notice the motion of 
fishes, for the celerity of which tlieir shape 
is admirably adapted : hence, vessels de- 
signed to be navigated in water are made to 
imitate, in some degree or other, the shape 
of fish ; but the rapidity of a ship in sailing 
before the wind is not to be compared to 
the velocity of a fish. The largest fishes 
are known to overtake a ship in full sail 
with the greatest ease, to play round it 
without effort, and to surpass it at pleasure. 
Every part of the body seems formed for 
dispatch : tlie fins, the tail, and the motion 
,of the whole back-bone assist in the busi- 
ness ; and it is to that flexibility of body 
which mocks the efforts of art, that fishes 
owe the great velocity of their motions. 
The chief instruments in a fish’s motion are 
its fins, air-bladder, and tail; with two 
pair, and three single fins, it will migrate a 
thousand leagues in a season, and without 
indicating any visible symptoms of languor 
or fatigue. The fins serve not only to assist 
the animal in progression, but in rising and 
sinking, in turning, and even in leaping out 
of the water. The pectoral fins serve to 
push the animal forward, 'and to balance the 
head when it is too large for the body, and 
prevent it from tumbling to the bottom, 
which it infallibly would if the fins were cut 
off. The ventral fins, which always lie flat 
in the water, serve rather to raise or de^ 
press the body, than to assist its progressive 
motion. The dorsal fin acts as a poiser, in 
preserving the animal’s equilibrium, while it 
aids the forward movement ; and the anal 
fin is designed to maintain the vertical po- 
sition of the body. By means of the air 
bladder, fishes can increase or diminish the 
specific gravity of their body. When they 
contract it, and press out the air, the bulk 
of the body is diminished, and the fish sinks 
as far as it pleases : on relaxing the opera- 
tion, the bladder acquires its natural size, 
the body becomes specifically lighter, and 
the fish is enabled to swim near the surface. 
The tail, in the last place, may be regarded 
as the rudder, directing the motions of the 
fish, to which the fins are only subser- 
vient. 
With respect to the nourishment of fishes ; 
they are mostly carnivorous, though they 
seize upon almost any thing that falls in 
their way, and not uncommonly devour 
their own offspring : tliey seem, indeed, to 
manifest a particular predilection for what- 
ever they can swallow possessed of life. 
They often meet with each other in fierce 
opposition, and the victor, without scruple, 
devours his antagonist. Thus are they irri- 
tated by the continual desire of satisfying 
their hunger ; and the life of a fish, from 
the smallest to the greatest, is but one 
scene of hostility and violence. The smaller 
species, which stand no chance in the un- 
equal combat, resort to those shallows where 
the larger are unable to approach. There 
they become invaders in their turn, and live 
on the spawn of large itishes, which they 
find floating on the water, till at length they 
are imprisoned, and leisurely devoured by 
the mussel, oyster, &c. which lie in ambush 
at the bottom. Fishes can, however, not 
withstanding their natural voracity, live 
long, apparently, without food ; but they, 
perhaps, in vases and other ornamental ves- 
sels, feed on insects too small for the human 
eye to see ; or, it has been thought, they 
may have the power of chemically decom- 
posing water. We now proceed to the sub- 
ject of reproduction. 
In most, if not in all fishes, there is a difi 
ference in sex, though Bloch and others 
make mention of individuals, which seemed 
to unite the two sexes, and to be real her- 
maphrodites. The number of males, it has 
been remarked, is about double that of 
females ; and were it not for this wise pro- 
vision of nature, a large proportion of the 
extruded eggs would remain unfecundated. 
