Fig. 4. Ca²⁺ activities in the CV fluid of P. multimicronucleatum adapted to either 24 mosmol l^-1 (left three bars) or 124 mosmol l^-1 (right three bars). The adaptation solution contained either 2 mmol l^-1 K⁺ (white bars) or 2 mmol l^-1 choline (checked bars) or 1.25 mmol l^-1 Ca²⁺ (black bars). Each column represents a mean value±s.d. for five or six contractile vacuoles, one per cell.