Suggestions.—Amœbas live in the slime found on submerged stems and leaves in standing water, or in the ooze at the bottom. Water plants may be crowded into a glass dish and allowed to decay, and after about two weeks the amœba may be found in the brown slime scraped from the plants. An amœba culture sometimes lasts only three days. The most abundant supply ever used by the writer was from a bottle of water where some oats were germinating. Use ⅕ or ⅙ inch objective, and cover with a thin cover glass. Teachers who object to the use of the compound microscope in a first course should require a most careful study of the figures.
Fig. 9.—Amœba Proteus, much enlarged.
Fig. 10.—Amœba.
cv, contractile vacuole; ec, ectoplasm; en, endoplasm; n, nucleus; ps, pseudopod; ps, pseudopod forming; ectoplasm protrudes and endoplasm flows into it.
Form and Structure.—The amœba looks so much like a clear drop of jelly that a beginner cannot be certain that he has found one until it moves. It is a speck of protoplasm (Fig. [9]), with a clear outer layer, the ectoplasm; and a granular, internal part, the endoplasm. Is there a distinct line between them? (Fig. [10].)
Note the central portion and the slender prolongations or pseudopods (Greek, false feet). Does the endoplasm extend into the pseudopods? (Fig. [10].) Are the pseudopods arranged with any regularity?
Sometimes it is possible to see a denser appearing portion, called the nucleus; also a clear space, the contractile vacuole (Fig. [10]).
Fig. 11.—The same amœba seen at different times.