페이지 이미지
PDF
ePub
[ocr errors]

Columbus starting on his voyage and people saying, "It can't be done." Another part showed Fulton starting his trial trip with his boat, and the people on the bank saying, "Visionary, impractical." A third part represented the signing of the Articles of Confederation and the people of Europe saying, "It will never be a success. The last scene represented the framing of the Constitution of the League of Nations and the people saying, "It can't be donevisionary-impractical-it will never be a success. Just because the Articles of Confederation led to a stronger union of the states is no sure sign that the League of Nations will act in the same way and lead to a stronger union among nations. The people of the states were bound together by a common sympathy, while each nation has its own selfish interests and desires. How the League works will depend upon the people. It can be made a success if the people of all the nations belonging to the League are determined to make it a success. Each nation must stand by the decisions of the League, and must be willing to furnish aid when force is required to settle any question. Each nation must be willing to take its armed forces outside its own territory to enforce the laws of the League. These things must be done whether the nation is involved in the difficulty or not.

The following oral composition illustrates how a student may select his material from different sources -from what he has heard some one else say about the

subject, from what he has read, and from what he personally knows, and then work these facts into an orderly unit. The student who gave this composition obtained her facts from lectures in the classroom, from her readings, and from her microscopic and experimental work on protozoa.

2. PROTOZOA

2

I am going to talk about the protozoa, the most simple and lowest members of the animal kingdom. I shall take the amoeba as a specific type of the class protozoa. Under the microscope-you can't see this animal unless you use the microscope-it appears like a small, almost transparent, lump of jelly, in which can be distinguished a thin outer rind and an inner substance. The first is known as the ectoplasm, and the latter as the endoplasm, or what is commonly

called protoplasm. The amoeba is a one-celled animal, and all functions are performed in this one cell.

Perhaps you wonder how this small animal eats and how it moves. It has no hands to bring its food to it. It has no neck like a horse to reach out and get its food. And it has no mouth like a fish to swallow its food. But still, it does eat and move, and I'm going to try to tell you how it does both.

In the first place, the animal has the power of continually changing its shape by throwing out projections. On the board I have sketched a few different shapes of the amoeba [see drawings above]. Number 4 of the largest sketch represents a projection. The ectoplasm slowly sends out a projection, and the protoplasm runs into it. Of course the size of the animal is not altered; so

when a process is thrust

out in front, the rest of the animal must follow it by shrinking away behind.

Its digestive system is also unusual. As its habitat is at the bottom of ditches, ponds and stagnant pools, it must feed on the minute plant life and smaller onecelled animals. When an amoeba comes across anything it wants to eat, it sends out a projection on each side of the object, and then the projections unite beyond the object. In this way the object is engulfed in the body of the amoeba, where it is digested. The food is taken up by the protoplasm, which dissolves it. The undigested food is thrown off by means of food vacuoles-as you can see in Number 2. These vacuoles expand and contract. The liquid wastes are

thrown off by a contractile vacuole, which is continually in action. This kind of vacuole is shown at Number 3.

The nucleus, in Number 1, is functional in the process of reproduction. The reproduction is very simple. The animal reproduces by fission and sporu. lation.

In fission, the nucleus divides into two before the body shows any signs of dividing. One nucleus goes to the anterior end and the other to the posterior end. Then the animal splits transversely, and both the daughter and the parent have a nucleus.

Reproduction by sporulation is done only in the dry seasons, when the water evaporates from the ditch or pool and leaves the amoeba exposed to the air. The animal then forms itself into a spherical body with a thick wall, or cyst, around it. Inside the cyst, the animal breaks up into several germs. The cyst is then blown about by the wind, and when it comes in contact with water again, it bursts, freeing the germs. Each germ then takes on the form of a

minute amœba.

The amoeba has a peculiar way of defending itself. It does this by engulfing particles of sand so as to render itself less palatable to larger animals.

At present, this is practically all there is to be said about this animal. Owing to the fact that the amœba was just recently found to be an animal, there is great possibility for the work of future zoölogists.

(1) Are you able to follow this talk? Is it given. in as clear language as such a technical subject could be?

(2) Do you think the illustrations drawn on the board helped the class to understand better?

56. Argumentation.-Avoid too elaborate an argument. Keep in mind the following suggestions:

(a) State the general subject of your talk-"Coeducation," "Government Ownership of Railroads." Then state in the form of a clear-cut sentence the proposition upon which your argument is based; as "I am going to discuss whether the Government should own the Railroads." You had better give this proposition at the beginning, but you do not necessarily have to make known which side of the question you are on. It is often a better policy to let your attitude remain unknown till you have gradually led your hearers over to your way of looking at the proposition.

(b) Keep before you the main points you are trying to prove, whether or not you state each in sentence form.

(c) Discuss each of these points separately.

(d) It is generally best to attempt to destroy the points on the opposing side by dealing with them as they arise in connection with your contentions.

(e) Be as informal as possible. Get away from the debate style.

« 이전계속 »