=Amœba.=--TECHNICAL NOTE.--_Amœbæ_ are found in stagnant pools of water on the dead leaves, sticks and slime at the bottom. To obtain them, collect slime and water from various puddles in separate bottles and take them to the laboratory. Place a small drop of slime on a slide under a cover-glass. Examine under the low power first and note any small transparent or opalescent objects in the field. Examine these objects with the higher power and note that some are mere granular jelly-like specks, which slowly (but constantly) change their form. These are _Amœbæ_. A teacher of zoology recommends the following method of obtaining a large supply of _Amœbæ_: "For rearing _Amœbæ_ place two or three inches of sand in a common tub, which is then filled with water and placed some feet from a north window; three or four opened mussels, with merest trace of the mud from the stream in which they are taken, are partially buried in the sand and a handful of _Nitella_ and a couple of crayfish cut in two are added; as decomposition goes on a very gentle stream is allowed to flow into the tub, and after from two to four weeks abundant _Amœbæ_ are to be found on the surface of the sand and in the scum on the sides of the tub; small _Amœbæ_ appear at first, and later the large ones." Having found an _Amœba_ (fig. 5) note its irregular shape, and if it moves actively observe its method of moving. How is this accomplished? The viscous, jelly-like substance which composes the whole body of an _Amœba_ is called _protoplasm_. The little processes which stick out in various directions are the "false feet" (_pseudopodia_). Note that the outer portion, the _ectosarc_, of the protoplasmic body is clear, while the inner, the _endosarc_, is more or less granular in structure. Has _Amœba_ a definite body-wall? Do the pseudopodia protrude only from certain parts of the body? Within the endosarc note a clear globular spot which contracts and expands, or pulsates, more or less regularly. This is the _contractile vacuole_. Note the small granules which move about within the endosarc. These are food-particles which have been taken in through the body-wall. Note how pseudopodia flow about food-particles in the water and how these are digested by the protoplasm. If an _Amœba_ comes into contact with a particle of sand, note how it at once retreats. Note within the endosarc an oval transparent body which shows no pulsations. This is the _nucleus_, a very complex little structure of great importance in the make-up of _Amœba_. [Illustration: FIG. 5.--_Amœba_ sp.; showing the forms assumed by a single individual in four successive changes. (From life.)]