Page:First course in biology (IA firstcourseinbio00bailrich).pdf/248

 the particle (Fig. 12). The water and the particle are soon absorbed and assimilated by the endoplasm.

taking food.

Excretion.—If a particle of sand or other indigestible matter is taken in, it is left behind as the ameba moves on. There is a clear space called the contractile vacuole, which slowly contracts and disappears, then reappears and expands (Figs. 9 and 10). This possibly aids in excreting oxidized or useless material. Circulation in the ameba consists of the movement of its protoplasmic particles. It lacks special organs of circulation. Feeling.—Jarring the glass slide seems to be felt, for it causes the activity of the ameba to vary. It does not take in for food every particle that it touches. This may be the beginning of taste, based upon mere chemical affinity. The pseudopods aid in feeling. Reproduction.—Sometimes an ameba is seen dividing into two parts. A narrowing takes place in the middle; the nucleus also divides, a part going to each portion (Fig. 13). The mother ameba finally divides into two daughter amebas. Sex is wanting. , dividing. Source of the Ameba's Energy.—We thus see that the ameba moves without feet, eats without a mouth, digests without a stomach, feels without nerves, and, it should also be stated, breathes without lungs, for oxygen is absorbed from the water by its whole