Fish have been divided into different classes: there are those which have bony plates instead of scales, as the Sharks and Rays, and many fishes which exist only as fossils; and those called the "splendid" fish, from the brilliancy of their coats of mail, which lock together like ancient armour. Most of them are extinct species, but the Sturgeon is one of these armoured fishes. Then the Mud-fishes form another class. But by far the most numerous is that to which the Bony-skeletoned fishes, with scales like those of the Salmon, belong. A few species are destitute of any bony or scaly covering; and one of them—the Electric Eel of South American rivers—protects itself by giving a sharp electric shock to any creature that comes in its way!
The eyes of fish are sometimes large, and they can see a long way, and also hear very quickly. Turbot, plaice, and other flat-fish, which have no swim-bladder, lie with one side in the mud at the bottom of the sea or rivers—Can you guess in which side of the head their eyes are placed?
"In the uppermost, and sometimes both eyes are there."
You are right, for there would be no use for an eye in the side turned to the mud.
As far as we know, fish are not clever creatures, but I have heard that some kinds, kept as pets, have learnt to know the sound of the dinner bell just as well as the lions and tigers at the Zoo know their bell; and you have seen how they rush about their cages, and roar with hungry impatience when it rings. I have read that some fishes of various kinds, such as Cod and Ling, kept for the use of the owners in a pond to which the tide came, near a house in Scotland, and regularly fed with limpets by an old woman who had charge of them, knew her voice, and would put out their heads and crowd to the side of the pond when she came near, and even let her take them up and stroke their cold backs; but I doubt that you will find your gold-fish so intelligent and affectionate.
I must not forget to speak of the fishes which make nests, for very few such have been discovered, and they are considered curiosities of fish-life. Perhaps when we know more of the habits of the finny-tribe, we shall find that some others provide for the safety of their young in a similar way, but at present I believe the Stickleback, which not only makes a nest but takes care of his young brood until they are six days old and can "find for themselves," is the only one known in Europe. In Demerara, a fish called the Hassar makes a floating cradle of grass or leaves for its eggs, over which it watches carefully, being ready to defend it bravely when attacked; thus in Australia, an eel called the Jew-fish was one day noticed swimming round and round a clear place among the reeds, and it turned out that it was guarding a nest of stones which it had placed in the river bed.
There are one or two strange fishes which you will not see in any shop; though if you have friends who "follow the sea," they may have told you of the Sun-fish, sometimes caught in the west of Ireland; very large and round it is, of a silvery-white colour, so that on dark nights, when the fishermen have seen it shining as it swam, just under the water, it has seemed to them like the sun shining behind the clouds on a showery day; and they have given it this name.
You may too, have heard strange tales of another round fish, called from its shape the Globe-fish, and from its skin the "Sea-hedgehog"; it is covered with sharp thorns, and has the power, by swallowing air, of so greatly increasing its size (without sharing the fate of the poor toad in Æsop's Fable) that it not only can rise to the surface of the water, but float as long as it pleases. Then there are the blue Flying-herrings, with long fins, which you would see if you took a voyage to Australia. These poor little creatures have enemies both in birds and fishes. When the sharks want to make a meal of them, they leap into the air, using their long fins almost as a bird uses its wings, and are able to keep up for some distance; some say they can fly five hundred feet; but alas! when they are on the fin, the sea-gulls are eager and ready to pounce upon them, and they have to take refuge in the sea again. With all their beauty, they have a hard life of it, constantly escaping away from the sea-gull, into the shark!
And now, when we have time, I think both you and I shall be pleased not only to observe carefully the fishes which we see every day, but to read about others; about the sword-fish, which has neither scales for its protection, nor teeth, but whose snout forms a bone, four or five feet long, set with sharp pointed teeth on each side—somewhat like a double-edged saw; this bone is a most formidable weapon when used against large fish, and is so strong that it has even pierced through the planks of a boat; about the tiny Sea-horse, with its head so curiously like that of a horse, and its wing-like fins; about the Whale, which is not really a fish at all (and why it is not will be something for you to find out), besides a great many monsters of the deep of which I have not time to tell you. We have already had a much longer talk about fish than my children had, although it was while we were speaking about fishing, and how the night is the usual time for it, that we read two accounts of great numbers of fish being caught in the sea of Galilee—not at night, but in broad daylight.
One account is given in the gospel of Luke. You know that—the disciples, Simon and Andrew his brother, and James and John his brother, were fishermen, and used to launch their boats upon the Sea of Galilee, and let down their nets into the deep blue water. It was when they had been fishing all night, and had caught nothing, that they left their boats beside the sea, and were busy washing their nets.