Fig. 1. Effect of ions on glycerol-treated sperm. Sperm were incubated in a glycerol solution for 10 s exactly. Then, 1 vol of this suspension was diluted in 40 vol of an activation solution (KCl 100 mmol l^–1, KCl 50 mmol l^–1+NaCl 50 mmol l^–1, KCl 10 mmol l^–1+NaCl 90 mmol l^–1 or NaCl 100 mmol l^–1). Gray bar, percentage motility of intact sperm; black bars, glycerol-treated sperm. Intact sperm showed motility only with 100 mmol l^–1 NaCl. Values are means ± S.D.(N=5).