1. In peritrich ciliates many food vacuoles without visible solid contents may be formed. The water in these vacuoles passes into the general cytoplasm.
2. In fresh-water Peritricha the rate of uptake of fluid in food vacuoles generally amounts to between 8 and 20% of the rate of output of fluid by the contractile vacuole. The greater part of the water evacuated is presumed to enter the animal by osmosis through the general body surface.
3. In marine Peritricha the rate of uptake of fluid by food vacuoles approximately balances the rate of output by the contractile vacuole. The elimination of the water taken in by food vacuoles is believed to be the main function of the contractile vacuole in marine ciliates.