describe a well-controlled experiment to find out if the rise in internal free calcium observed in the cytoplasm of unfertilized sea urchin eggs in the presence of A23187 is due to influx of calcium from seawater. Comprise experimental treatments, controls, and in brief describe experimental methods.

Note: As illustrated in the lab manual, the calcium concentration in seawater is 10mM while the concentration in unfertilized egg cytoplam is bigger that 10-6 M. Instantly after fertilization or in unfertilized eggs treated with A23187 the internal calcium concentration rises.