Contractile vacuole a spherical clear pulsating vacuole filled with watery fluid is present in endoplasm near nucleus. It is called contractile vacuole. It is enclosed in unit membrane which is surrounded by many mitochondria and vesicles. It makes part is respiration and excretion but its more important function is to control the amount of water in the cytoplasm since water continuously enters the body of amoeba by osmosis. The excess water accumulates in contractile vacuole and when it becomes full it comes the surface and burst and disappears. This process is known as osmoregulation.
Food vacuoles :- A number of spherical vacuoles large and small, containing water, food and digestive juices are present in the endoplasm. These are food vacuoles. They are meant for temporary storage of food and serve as temporary stomach. Sometime they are called gastric vacuoles.
Water Vacuoles :- These are spherical and scattered throughout the endoplasm. They do not change their shape like contractile vacules.