It is called Amœba (Fig. 1), and although it is hardly a hundredth of an inch in diameter, yet if we devote some time to it we shall find that it is a very remarkable animal. Thus if it wishes to move in any given direction, a portion of the body becomes a seeming leg and protrudes in that direction, the rest of the body following, drawn along in some mysterious manner. If it wishes to eat, it is not obliged to twist around to bring the food or victims opposite the mouth, as a mouth forms there and then; the Amœba merely glides around it and covers it up. We may even notice a difference in the parts. Thus the center calls to mind ground glass; it is blurred or granular, while around the edges is a little border which is transparent, like ordinary window glass. So the Amœba is a minute mass of jelly inclosed in a layer a little clearer. [Illustration: FIG. 1.--_Amœba proteus_, with the pseudopodia (false feet) protruded, enlarged 200 diameters (after Leidy): _n_, nucleus; _c_, contractile vesicle; _v_, one of the larger food-vacuoles; _en_, the granular endosarc; _ec_, the transparent ectosarc; _a_, cell of an Alga taken in as food (other cells of the same Alga are obliquely shaded).] Floating in the granular portion is seen a minute round body called the nucleus, clearer than the fluid in which it rests, and not far away another clear, circular body, which from time to time contracts or sometimes disappears in a marvelous fashion, but always returns. This is called the contracting vesicle, and here our discoveries end, so far as organs and structure are concerned, as these are nearly all that have been found; yet the Amœba eats, doubtless sleeps, and grows. [Illustration: FIG. 2.--Amœba eating: _Pv_, contracting vesicle.] We may watch it at its dinner. When a victim is found, an animal smaller than itself, out shoots a little cape or extension from the clear rim, creeping slowly up the side of the animal; and if we watch very closely, we shall see the thicker portion of the Amœba, that which calls to mind ground glass, running or flowing into it. Then another false foot, as it is called, slowly creeps out on the opposite side and joins its companion, more of the ground-glass matter slides or pours into this, filling it out, and, presto! the two arms merge one into the other. The victim has been swallowed and is now being digested (Fig. 2, _d_). [Illustration: FIG. 3.--Amœba separating.]