Fig. 1. Simultaneous measurements of the changes in cGMP and IP₃ contents of A. crassispina (A) and H. pulcherrimus (B) eggs, compared with [Ca²⁺]_i, after insemination. cGMP (red) and IP₃ (blue) values at each point after insemination were obtained on the same aliquot of egg suspension, and [Ca²⁺]_i (broken line) is an average over five independent experiments for A. crassispina or nine for H. pulcherrimus. Arrows indicate the onset of the fertilization potential. Scales for cGMP are on the left axis in each panel, and scales for InsP₃ and [Ca²⁺]_i are on the right axis.