Amoeba is microscopic and a cellular or non-cellular. Structurally, it is unicellular but its one cell performs all the vital activities. Hence, it is called a cellular.
The size of Amoeba Proteus is 0.2 to 0.3 mm (200 to 300 μ). Other species may reach unto 0.5 μ.
The shape of amoeba is irregular as it is not covered by any rigid covering except plasma membrane. Hence, there is no definite anterior and posterior ends.
The amoeba is colorless, translucent and appear like jelly.
The amoeba is polypodial i.e. it forms one to many pseudopodia. The pseudopodia are blunt and are called as lobopodia. The largest pseudopodium is considered to be the anterior end & the opposite end is called as posterior or uroid end. The pseudopodia help in locomotion & ingestion of food.
The amoeba is covered by a plasma membrane (1 to μ thick) which is a selectively permeable membrane.
Internally, the amoeba consists of cytoplasm and nucleus. The cytoplasm is divisible into ectoplasm and endoplasm. The ectoplasm or ectosarc is the outer part which is transparent, homogeneous and without cell orgenelles. It is broadest at the anterior end of main pseudopodium which is called as hyaline cap. The endoplasm is inner substance which is transluscent, heterogenous and consist of all cell orgenelles. It is further divided into outer plasmagel and inner plasmasol (Mast. 1926).
