1. Keio Senior High School, Hiyoshi, Kohoku-ku, Yokohama-shi, Kanagawa 223, Japan
2. Department of Biology, Nagoya Jiyugakuin College, Shikatsu-cho, Nishikasugai, Aichi 481, Japan
3. Department of Food and Nutritional Sciences, University of Shizuoka, Yata, Shizuoka-shi, Shizuoka 422, Japan
4. Department of Biology, Faculty of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan