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Fig. 10.—Ameba.
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 ameba (also spelled 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).
Movements.—Sometimes while the pseudopods are being extended and contracted, the central portion remains in the same place (this is motion). Usually only one pseudopod is extended, and the body flows into it; this is locomotion (Fig. 11). There is a new foot made for each step.
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Fig. 11.—The same ameba seen at different times.
Feeding.—If the ameba crawls near a food particle, the pseudopod is pressed against it, or a depression occurs (Fig. 12), and the particle is soon embedded in the endoplasm. Often a clear space called a food vacuole is noticed around the food particle. This is the water that is taken in with
