The overall aim is to study the differentiation of electrophysiological properties in different excitable tissues, in different animals, in different stages of development and in different genetic mutants of the same animal. The following research is proposed: (1) Action potentials are found in egg cell membrane of echinoderms and tunicates but not those of Drosophila. Changes in excitability associated with tissue differentiation during early development will be studied in these animals as well as other animals such as the frog. (2) The role of Ca and associated membrane changes in secretory cells will be examined in pancreas exocrine cells in primary culture. The exocytotic process of secretion will be studied by monitoring changes in the cell surface area observed as changes in the high frequency AC impedance of the cell membrane. (3) Electrical properties of the echinoderm egg cell membrane during fertilization and early development will be continued. The ionic mechanism of the activation potential and the role of Ca in the formation of the fertilization membrane will be analyzed. (4) The excitability of the wing muscle of the wild type Drosophila melanogaster will be analyzed by 'patch' voltage clamp, and this will be extended to various mutants such as heat sensitive paralytic mutants. (5) Theory for cation permeation during the anomalous or inward rectification will be completed and examined by experiment with the egg cell membrane of a starfish.