Fig. 2. Acidification of digestive vesicles. Digest cells were incubated with 100 µmol l^–1 of globin for 2 h, and then exposed to 50 µmol l^–1 of Acridine Orange for 1 min, washed and observed by fluorescence microscopy. Small (arrows) and large (asterisks) acid digestive vesicles are indicated. Scale bar, 10 µm.