The plasmalemma around amoeba is semipermeable and as the water of the pond in which this animal lives hypotonic to the cytoplasm of its body. According to the law of diffusion large amount of water enters the body. If all this water is allowed to remain in the body, the body will swell and ultimately burst.
Hence, a special arrangement is required for the removal of this excess water is amoeba and this is done by the contractile vacuole. The vacuole bursts to the outside disappears and soon reappears. The process goes on continuously. There are two states of contractile vacuole in osmoregulation. 1. Diastole. 2. Systole.
1. Diastole:
During this state many small vacuoles appear.
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2. Systole:
The process of disappearance of contractile vacuoles after bursting is called systole.
In this manner the contractile vacuole performs the function of osmoregulation in ameba. According to some scientists some waste products and carbon dioxide are also excreted by this vacuole. Kitching in 1952 studied the process of osmoregulation in amoeba.