. A civic biology : presented in problems. Biology; Sanitation. 170 SINGLE-CELLED ANIMALS AS ORGANISMS ^2^'$fcr '""" •—\r\\ vr portant organ is difficult to see, except in cells that have been stained. Although but a single cell, still the amoeba appears to be aware of the existence of food when it is near at hand. Food may be taken into the body at any point, the semifluid protoplasm simply rolling over and engulfing the food material. Within the body, as in the paramcecium, the food becomes inclosed within a fluid space or vacuole. The protoplasm has the power to take out such
. A civic biology : presented in problems. Biology; Sanitation. 170 SINGLE-CELLED ANIMALS AS ORGANISMS ^2^'$fcr '""" •—\r\\ vr portant organ is difficult to see, except in cells that have been stained. Although but a single cell, still the amoeba appears to be aware of the existence of food when it is near at hand. Food may be taken into the body at any point, the semifluid protoplasm simply rolling over and engulfing the food material. Within the body, as in the paramcecium, the food becomes inclosed within a fluid space or vacuole. The protoplasm has the power to take out such material as it can use to form new protoplasm or give energy. Circulation of food material is accomplished by the constant streaming of the protoplasm within the cell. The cell absorbs oxygen from the water by osmosis through its delicate mem- brane, giving up carbon dioxide in return. Thus the cell " breathes " through any part of its body covering. Waste nitrogenous products formed within the cell when work is done are passed out by means of the contractile vacuole. The amoeba, like other one- celled organisms, reproduces by the process of fission. A single cell divides by splitting , XT v / <r swc I \ A 11 FTv^ : ' J^^^cT^^^p- <M" '$. Amoeba, showing the changes which take place during division of the cell. The dark body in each figure is the nu- cleus ; the transparent circle, the con- tractile vacuole; the large granular masses, the food vacuoles. Much magnified. into two others, each of which resembles the parent coll, except that they are of less bulk. When these become the size of the parent amoeba, they each in turn divide. This is a kind of asexual reproduction. When conditions unfavorable for life come, the amoeba, like some one-celled plants, encysts itself within a membranous wall. In this condition it may become dried and be blown through the air. Upon return to a favorable environment, it. Please note that these images are extracted from
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