"Had I like fish, with fins and gills, been made,

Then might I in your element have play'd;

With ease have dived beneath your azure tide."-FAWKES.

MISCELLANEOUS.

1132. How is the breathing of fishes conducted?

The breathing of fishes takes place by gills. The water, which is impregnated by atmospheric air, is taken in by the mouth, and forced out again by the apertures on each side of the neck. It is thus made to pass between the gills, which form a set of comb-like vascular fringes, supported upon a system of bones termed the branchical arches, and during this passage the air is absorbed by the blood of the fish.

These fringes are generally four in number on each side, and are attached by one extremity to an intermediate chain of bones situated opposite the middle of the neck, behind the hyoid bone, while by their opposite extremity they are joined by ligaments to the under surface of the skull.

1133. Why is the flesh of fishes white?

Because the oxidized blood is chiefly confined to a few internal organs, as the heart, liver, kidneys, lungs, and gills; the flesh is consequently white and apparently bloodless.

1134. Why do fishes swallow their food hastily, and without mastication?

Because they are obliged unceasingly to open and close the Jaws for the purpose of respiration, and cannot long retain food in the mouth when quite shut.

1135. Why are the teeth of fishes slightly curved inwards? Because this form is best adapted for taking a firm hold of prey, which is frequently alive, and which without such a provision would, in its struggles, easily escape from the mouth of the captor.

1136. Why does a fish gasp violently when taken out of the water?

Because it endeavours to separate the gill filaments, by which

"See how she gasps, and struggles hard for life."-LLOYD.

it is supplied with breath, and which adhere together when deprived of their natural element.

1136. Why are certain species of fish constituted to live for a long period out of water?

Because they inhabit ponds and streams in warm countries, where, in many situations, there is an ample supply both of food and water for fish during the rainy season; but a complete deficiency of both when this is succeeded by a periodical drought. Such receptacles can only be tenanted by fish which are furnished with the peculiar apparatus for keeping the gill moist; since, when one pond or stream is dried up, they can migrate in search of another. In the course of these journeys, they climb up steep banks, and even trees; and, by a remarkable instinct, they seem always to travel to the nearest water.

1137. Why is that part of the fish's eyes known as the crystalline lens, much rounder than in the eyes of the terrestrial animals?

Because the rays of light, in passing from water into the eye, require to be refracted by a more convex surface than when it passes out of air into the eye.

1138. As an illustration of the instances adduced here, of the adaptation of the fish's eye to the medium in which it lives, we may observe that the power in the human eye, for example, of drawing the pencil of rays to a focus, and producing an accurate image upon the retina in the bottom of the eye, depends principally upon two circum

brought into operation. In the eye of an animal living in the atmosphere, the lens

"The sounds and seas, with all their finny drove,

Now to the moon in wavering morrice move."-MILTON.

is removed backwards, and resembles the optician's double convex lens; but in the fish it is a sphere, and being brought in contact with the transparent cornea, it not only has the power to concentrate the rays of light coming through the water, but by its altered position it increases greatly the sphere of vision (fig. 2). It may be added that it is not exactly the cornea that is deficient in the fish, but the aqueous humour behind it. An aqueous fluid being thus both behind and before the cornea, and that membrane being in a very slight degree thicker in the centre than in the margin, this part of the organ which is so efficient in the atmosphere is rendered useless in water. A man diving, for example, sees imperfectly, somewhat in the condition of an aged person who requires spectacles.

1139. Why does a fish lie with his head against the stream?

Because when a fish is situated with his head down the stream, he is compelled to travel more rapidly than the waters, or the latter will find its way into the gills, and, by becoming stationary, suffocate him.

1140. A trout may be seen lying for hours stationary, while the stream is running past him; and it sometimes appears to remain so for whole days and nights. In salmon-fishing the fly is played upon the broken water in the midst of a torrent, and there the fish shows himself, rising from a part of the river where men could not preserve their footing, though assisted by poles, or locking their arms together.

1141. Why do the jack and stickleback keep up a continual motion of the fins nearest their gills?

Because they frequent still shallows, and require the water to be perpetually brought to their gills. In this case, the water does not come of itself, and, therefore, the fish moves his pectoral fins continually to create a perpetual change in the water, propelling that which has already passed through the gills, bringing fresh in its place, and thus keeping up a constant current.

1142. Neither to the jack nor the stickleback does the motion appear to cause any exertion; it seems natural to them, and a distinct function apart from the motion of the fins for swimming purposes. It is, in fact, somewhat analogous to the perpetual motion of the heart, lungs, and internal viscera in the human body.

"A man may fish with the worm that hath eat of a king; and eat of the fish that hath fed of that worm."-SHAKSPERE.

1143. Why do fishes which suim vertically inhabit near the surface, while those which swim bottom?

horizontally keep to the

The fish which swims on edge has the tail much more effectively formed as a swimming organ, and the fins much firmer, as well as more produced; they are, therefore, rapid swimmers, and rather discursive in their motion. From an opposite development,

fishes swimming on the flat of their bodies can only progress slowly, and do not, on that account, range far.

1144. Why will a fish which has broken away with a hook, frequently take another hook immediately afterwards?

Because the mouths of fishes are usually cartilaginous, and furnished (at least in the part where the hook strikes) with few nerves, or they are altogether absent. In such a case the fish experiences little inconvenience from the presence of a hook, and boldly strikes at a fresh bait.

1145. Sir Humphrey Davy says:-"I have caught pike with four or five hooks in their mouths, and tackle which they had broken away with only a few minutes before; and the hooks seemed to have had no other effect than that of serving as a sauce piquante, urging them to seize another morsel of the same kind."*

1146. Why do wounds in fish heal rapidly, and why do they appear to be generally exempt from disease?

Because the temperature of the medium in which they reside is uniform, and they are consequently not subject to those alterations of the atmosphere, which are a fruitful source of morbidity to other portions of the animal creation.

"Salmonia."

"Being moody, give him line and scope; till that his passions, like a whale on ground, confound themselves with working."-SHAKSPERE.

1147. Why may a fish be "drowned" when being "played" by an angler?

Because fishes breathe by passing water, which always holds common air in solution, through their gills, by the use of a series of muscles connected with them.

When a fish is hooked in the upper part of the mouth, it is scarcely possible for him to set the muscles in action which move the gills, while the rod is applied as a lever to the line, so that no aërated water can be respired.

1148. A fish, hooked in a part of the mouth where the force of the rod will render his efforts to respire unavailing, is much in the same state as that of a deer caught round the neck by the lasso of a South American peon, who gallops forwards dragging his victim after him, which is killed by strangulation in a very short time. When fishes are hooked foul-that is, on the outside of the body, as in the fins or tail-they will often fight for many hours, and in such cases very large salmon are seldom caught, as they retain their powers of breathing unimpaired; and if they do not exhaust themselves by violent muscular efforts, they may bid defiance to the temper and the skill of the fisherman.*

1149. Why is the migration of fishes of great importance to mankind?

It is by these migrations that the blessings of fish diet are periodically bestowed upon the inhabitants of shores remote from each other. If such fishes were constant residents in any one locality, we might feed on them to satiety; but, by a temporary privation, we learn to estimate the value of the treat, and to hope for the periodical return.

1150. Why do fishes generally spawn in shallow waters?

Because a certain degree of solar heat and light is necessary for quickening the eggs into life; and also because the young fry are thereby protected from large fish.

1151. Why does the sea sometimes exhibit a luminous appearance?

Because of the great numbers of medusa, or jelly animalculæ, which, being congregated in one part, under certain conditions emit a phosphorescent light.

"Salmonia."

N