Fig. 5. O/N ratios of Sipunculus nudus body wall musculature, calculated from oxygen consumption and ammonia excretion rates under normo- and hypercapnia, versus different values of extracellular (A) and intracellular (B) pH. ^*O/N ratio significantly different from the respective control value at pHe 7.9. Values are means ± S.D., N=5-6.