Amoeba. The amoeba is a minute unicellular animalcule which lives in ponds, crawling over mud or submerged leaves. It is rarely more than one-fiftieth of an inch in diameter. When examined under a microscope it is seen to be a small
particle of jelly-like Peotoplasm, continually changing its shape by throwing out processes named pseudopodia (Fig. A); hence it is sometimes called the "Protean animalcule." It consists of an outer clear layer known as the ectosarc, enclosing a more fluid granular mass - the endosarc. In the latter are included an endoplast or "nucleus," a spherical or disc-shaped granular body, a contractile under the microscope it is seen to be a small vacuole, which alternately expands and contracts, and fragments of undigested food. The amoeba is the best introduction to the study of biology, as it shows the phenomena of life in one of its simplest forms; thus the amoeba has no special organs - of sense, locomotion, reproduction, or nutrition. It moves by a mere flow of the body, it takes its food at any point, and similarly ejects any innutritions particles; it reproduces its kind by dividing into two, each half growing again to a full-sized amoeba; it is therefore to a certain extent immortal, as death does not enter into the ordinary course of its existence. The amoeba belongs to the class Rhizopoda of the sub-kingdom Peotozoa.