Fig. 1. (A) Steady-state intracellular pH values of Sipunculus nudus isolated body wall tissue under normo- and hypercapnia, measured after long-term exposure to media of different pH. ^*pHi significantly different from the control value at pHe 7.9. (B) Intracellular bicarbonate concentrations of isolated tissue exposed to media of different pH and bicarbonate concentrations. Values are means ± S.D., N=5-6, except for extracellular bicarbonate levels, which are media concentrations, used to set the specific pHe, and therefore given without S.D.