Fig. 6. A series of pictures of four (labelled 1–4 in frame 0) membrane vesicles derived from the contractile vacuole complex of a P. multimicronucleatum cell, showing shrinkage and subsequent fusion when exposed to an increased external osmolarity produced by adding 0.5 mol l^–1 sorbitol solution. Numbers on frames correspond to the time (s) when the picture was taken after the start of the increase in external osmolarity. p, a micropipette for application of the sorbitol solution. Scale bar, 10 µm.