1. School of Science, Kwansei Gakuin University, Uegahara 1-1-155, Nishinomiya 662, Japan, Faculty of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi, Osaka 558, Japan, and College of Integrated Arts and Sciences, Osaka Prefecture University, Gakuencho 1-1, Sakai-shi 593, Japan