Lesson XXXVI

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.

Observations—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?

“I have my world, and so have you,
A tiny universe for two,
A bubble by the artist blown,
Scarcely more fragile than our own,
Where you have all a whale could wish,
Happy as Eden’s primal fish.
Manna is dropt you thrice a day
From some kind heaven not far away,
And still you snatch its softening crumbs,
Nor, more than we, think whence it comes.
No toil seems yours but to explore
Your cloistered realm from shore to shore;
Sometimes you trace its limits round,
Sometimes its limpid depths you sound,
Or hover motionless midway,
Like gold-red clouds at set of day;
Erelong you whirl with sudden whim
Off to your globe’s most distant rim,
Where, greatened by the watery lens,
Methinks no dragon of the fens
Flashed huger scales against the sky,
Roused by Sir Bevis or Sir Guy;
And the one eye that meets my view,
Lidless and strangely largening, too,
Like that of conscience in the dark,
Seems to make me its single mark.
What a benignant lot is yours
That have an own All-out-of-doors,
No words to spell, no sums to do,
No Nepos and no parlyvoo!
How happy you, without a thought
Of such cross things as Must and Ought⁠⁠—
I too the happiest of boys
To see and share your golden joys!”

—“The Oracle of the Goldfishes,” Lowell.