NCE upon a time, if stories are true, there lived a king called Midas, whose touch turned everything to gold. Whenever I see goldfish, I wonder if, perhaps, King Midas were not a Chinese and if he perchance did not handle some of the little fish in Orient streams. But common man has learned a magic as wonderful as that of King Midas, although it does not act so immediately, for it is through his agency in selecting and breeding that we have gained these exquisite fish for our aquaria. In the streams of China the goldfish, which were the ancestors of these effulgent creatures, wore safe green colors like the shiners in our brooks; and if any goldfish escape from our fountains and run wild, their progeny return to their native olive-green color. There are many such dull-colored goldfish in the Delaware and Potomac and other eastern rivers. It is almost inconceivable that one of the brilliant colored fishes, if it chanced to escape into our ponds, should escape the fate of being eaten by some larger fish attracted by such glittering bait.
The goldfish, as we see it in the aquarium, is brilliant orange above and pale lemon-yellow below; there are many specimens that are adorned with black patches. And as if this fish were bound to imitate the precious metals, there are individuals which are silver instead of gold: they are oxydized silver above and polished silver below. The goldfish are closely related to the carp and can live in waters that are stale. However, the water in the aquarium should be changed at least twice a week to keep it clear. Goldfish should not be fed too lavishly. An inch square of one of the sheets of prepared fish food, we have found a fair daily ration for five medium sized fish; these fish are more likely to die from overfeeding than from starving. Goldfish are naturally long-lived; Miss Ada Georgia has kept them until seven years old in a school aquarium; and there is on record one goldfish that lived nine years.
Too often the wonderful common things are never noticed because of their commonness; and there is no better instance of this than the form and movements of a fish. It is an animal in many ways similar to animals that live on land; but its form and structure are such that it is perfectly adapted to live in water all its life; there are none of the true fishes which live portions of their lives on land as do the frogs. The first peculiarity of the fish is its shape. Looked at from above, the broader part of the body is near the front end which is rounded or pointed so as to cut the water readily. The long, narrow, hind portion of the body with the tail acts as a propeller. Seen from the side, the body is a smooth, graceful oval and this form is especially adapted to move through the water swiftly, as can be demonstrated to the pupil by cutting a model of the fish from wood and trying to move it through the water sidewise.
Normally, the fish has seven fins, one along the back called the dorsal, one at the end of the tail called the tail or caudal fin, one beneath the rear end of the body called the anal, a pair on the lower side of the body called the ventrals, and a pair just back of the gill openings called the pectorals. All these fins play their own parts in the movements of the fish. The dorsal fin is usually higher in front than behind and can be lifted or shut down like a fan. This fin when it is lifted gives the fish greater height and it can be twisted to one side or the other and thus be made a factor in steering. The anal fin on the lower side acts in a similar manner. The tail fin is the propeller and sends the body forward by pressing backward on the water, first on one side and then on the other, being used like a scull. The tail fin varies in shape very much in different species. In the goldfish it is fanlike, with a deeply notched hind edge, but in some it is rounded or square.
The paired fins correspond anatomically to our arms and legs, the pectorals representing the arms, the ventrals the legs. Fins are made up of rays, as the bony rods are called which support the membrane; these rays are of two kinds, those which are soft, flexible, many jointed and usually branched at the tip; and those which are bony, not jointed and which are usually stiff spines. When the spines are present in a fin they precede the soft rays.
Fishes' eyes have no eyelid but the eyeball is movable, and this often gives the impression that the fish winks. Fishes are necessarily near-sighted since the lens of the eye has to be spherical in order to see in the water. The sense of smell is located in a little sac to which the nostril leads; the nostrils are small and often partitioned and may be seen on either side of the snout. The nostrils have no connection whatever with breathing, in the fish.
The tongue of the fish is very bony or bristly and immovable. There is very little sense of taste developed in it. The shape, number and position of the teeth vary according to the food habits of the fish. The commonest type of teeth are fine, sharp and short and are arranged in pads, as seen in the bullhead. Some fish have blunt teeth suitable for crushing shells. Herbivorous fishes have sharp teeth with serrated edges, while those living upon crabs and snails have incisor-like teeth. In some specimens we find several types of teeth, in others the teeth may be entirely absent. The teeth are borne not only on the jaws but also in the roof of the mouth, on the tongue and in the throat.
The ear of the fish has neither outside form nor opening and is very imperfect in comparison with that of man. Extending along the sides of the body from head to tail is a line of modified scales containing small tubes connecting with nerves; this is called the lateral line and it is believed that it is in some way connected with the fish's senses, perhaps with the sense of hearing.
Since fishes must push through water, which is more difficult than moving through air, they need to have the body well protected. This protection is, in most fishes, in the form of an armor of scales which are smooth and allow the body to pass through the water with little friction. These scales overlap like shingles in a roof and are all directed backward. The study of the fish scale shows that it grows in layers.
In order to understand how the fish breathes we must examine its gills. In front, just above the entrance to the gullet, are several bony ridges which bear two rows of pinkish fringes; these are the gill arches and the fringes are the gills. The gills are filled with tiny blood vessels, and as the water passes over them, the impurities of the blood pass out through the thin skin of the gills and the life-giving oxygen passes in. Since fish cannot make use of air unless it is dissolved in water, it is very important that the water in the aquarium jar should often be replenished. The gill arches also bear a series of bony processes called gill-rakers. Their function is to prevent the escape of food through the gills while it is being swallowed, and they vary in size according to the food habits of the fish. We note that the fish in the aquarium constantly opens and closes the mouth; this action draws the water into the throat and forces it out over the gills and through the gill openings; this then, is the act of breathing.
A Study of the Fish
Leading thought—A fish lives in the water where it must breathe, move and find its food. The water world is quite different from the air world and the fish have developed forms, senses and habits which fit them for life in the water.
Method—The goldfish is used as a subject for this lesson because it is so conveniently kept where the children may see it. However, a shiner or minnow would do as well.
Before the pupils begin the study, place the diagram shown on p. 150 on the blackboard, with all the parts labelled; thus the pupils will be able to learn the parts of the fish by consulting it, and not be compelled to commit them to memory arbitrarily. It would be well to associate the goldfish with a geography lesson on China.
1. Where do fishes live? Do any fishes ever live any part of their lives on land like the frogs? Could a salt-water fish live in fresh water, or vice versa?
2. What is the shape of a fish when seen from above? Where is the widest part? What is its shape seen from the side? Think if you can in how many ways the shape of the fish is adapted for moving swiftly through the water.
3. How many fins has the fish? Make a sketch of the goldfish with all its fins and name them from the diagram on the blackboard.
4. How many fins are there in all? Four of these fins are in pairs; where are they situated? What are they called? Which pair corresponds to our arms? Which to our legs?
5. Describe the pectoral fins. How are they used? Are they kept constantly moving? Do they move together or alternately? How are they used when the fish swims backwards?
6. How are the ventral fins used? How do they assist the fish when swimming?
7. Sketch a dorsal fin. How many spines has it? How many soft rays are there in it? What is the difference in structure between the stiff spines in the front of the dorsal fin and the rays in the hind portion? Of what use to the fish are these two different kinds of fin supports?
8. Sketch the anal fin. Has it any spines in front? How many rays has it? How is this fin used when the fish is swimming?
9. With what fin does the fish push itself through the water? Make a sketch of the tail. Note if it is square, rounded, or notched at the end. Are the rays of the tail fin spiny or soft in character?
10. Watch the goldfish swim and describe the action of all the fins while it is in motion. In what position are the fins when the fish is at rest?
11. What is the nature of the covering of the fish? Are the scales large or small? In which direction do they seem to overlap? Of what use to the fish is this scaly covering?
12. Can you see a line which extends from the upper part of the gill opening, along the side to the tail? This is called the lateral line. Do you think it is of any use to the fish?
13. Note carefully the eyes of the fish. Describe the pupil and the iris. Are the eyes placed so that the fish can see in all directions? Can they be moved so as to see better in any direction? Does the fish wink? Has it any eyelids? Do you know why fish are near-sighted?
14. Can you see the nostrils? Is there a little wartlike projection connected with the nostril? Do you think fishes breathe through their nostrils?
15. Describe the mouth of the fish. Does it open upward, downward, or directly in front? What sort of teeth have fish? How does the fish catch its prey? Does the lower or upper jaw move in the process of eating?
16. Is the mouth kept always in motion? Do you think the fish is swallowing water all the time? Do you know why it does this? Can you see a wide opening along the sides of the head behind the gill cover? Does the gill cover move with the movement of the mouth? How does a fish breathe?
17. What are the colors of the goldfish above and below? What would happen to our beautiful goldfish if they were put in a brook with other fish? Why could they not hide? Do you know what happens to the colors of the goldfish when they run wild in our streams and ponds?
18. Can you find in books or cyclopedias where the goldfish came from? Are they gold and silver in color in the streams where they are native? Do you think that they had originally the long, slender, swallow tails which we see sometimes in goldfish? How have the beautiful colors and graceful forms of the gold and silver fishes been developed?