FISH
The Nature Study lessons must be based upon observations of the living fish, preferably in May or June, September or October. The best place for this is on the bank of a clear stream from which it is possible to observe the fish in their natural environment. Here their life activities, their struggles, their conquests, and silent tragedies are enacted before the eyes of the observer. Many observations may be made in this way which will create a life-long interest in these reticent, yet active creatures. Since this method of study is practicable in but few cases, the study of the living fish in the aquarium is the best available substitute.
The teacher or the boys of the class can catch a few fish of three or four inches in length and carry them in a jar of water to the aquarium. Minnows, chub, perch, catfish, or other common forms will do.
OBSERVATIONS
I
The general shape, and the suitability of the shape for swimming.
The surface of the body and the protection it affords. Note the scales and the slime, the latter a protection against the growth of fungi, etc.
The gills—two openings behind the flaps at the rear of the head. The colours, and their value in concealing the fish. The dark upper surface makes it inconspicuous from above; the light under surface blends with the shadow and dims it.
The divisions of the body—head, trunk, and tail.
Movements of the fish and the part that the various fins play in these movements.
Note that the broad tail fin is the most useful fin for locomotion, the others act as balancers or as brakes, or for causing currents of water near the gills. Observe the movements of the pair of fins nearest the gills, the movements of the mouth, and the currents of water entering the mouth and passing through the gill slits. When a fish is kept in a very small quantity of water, observe the effect produced on the movements of the mouth and gill flaps. What are the uses of these movements? The pupils will thus discover the nature of the respiration of the fish. Why do fish die if many are kept in a jar of water?
II
By supplying various foods learn what kinds are preferred. Find in the actions or habits of the living fish evidences of a sense of smell, of sight, of hearing, and of taste.
Nearly all the following points of detailed study can be observed from the living fish: shape; size; tongue; teeth; gill slits leading from the mouth to the gills; nostrils, number and position; eyes, absence of eyelids; fins, size, build; the arrangement of the scales.
PROBLEMS
Why does the fish require a large mouth?
How are the eyes protected? Compare the shape of the eye with the shape of the eye of a land animal.
Why are there no openings from the surface directly into the ears? Show the suitability of the fins as organs of locomotion in water.
REFERENCES
Silcox and Stevenson: Modern Nature Study
Nash: Fishes of Ontario (from Department of Education, free)
Kellogg: Elementary Zoology