Abstract
The presence of potassium in the bathing solution is necessary to maintain a basal rate of beating in Sphaerium transversum. There is a significant difference in the response of small and large specimens to: (1) short- and long-term responses to various concentrations of potassium; (2) removal and subsequent addition of potassium; (3) variation of maintenance dosage of potassium in the washing solution; (4) lag period of response to a specific dose. The results suggest that an intracellular transmembrane potential change (surface effect) is necessary to activate ciliated cells of small clams. This latter change in small clams would account for the relatively short lag period for potassium activation.
