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Acknowledgments

I would like to thank Prof. Kazuyoshi Miyashita, for providing me the opportunity to study this animal at Chichi-jima Biological Station. His generous advice and friendship throughout the study at the Tokyo Metropolitan University made it possible for me to accomplish the present study.

I am grateful to Dr. Takahiro Asami, who gave me valuable suggestions and reading this manuscript carefully. He is encouraging me for every step in this study. I was impressed with his profound insights and informative answers to my questions. I deeply thank for his advice and criticisms.

I also thank Dr.Tadashi Suzuki, Dr.Tamotstu Kusano, Mr.Shintaro Satou, Dr.Keiichi Masuko, Dr.Fumio Hayashi, Mr.Masatoshi Nakane, Dr.Noriko Tamura, Mr.Kinji Fukuyama, Mr.Takashi Yabe, Miss Mariko Fujimori, Miss Mina Takeuchi, Mr.Teruki Oka, Miss Noriko Miyashita, Mr.Hiroyuki Ishii, and Mr.Eisuke Hasegawa, who have been members of the Laboratory of Animal Ecology. They gave me valuable comments and kind helps on various occasions.

Since I started this study at Chichi-jima Biological Station from the summer of 1987, I have been greatly enlightened and attracted by excellent biologists and naturalists visited the Station while I stadied here. Their serious attitudes toward science, intellectual discussions and devotion researches impressed me so much that it would be difficult for me to summarize what I learned from them in the present article.

Dr.Yoshikazu Shimizu and Mr.Takaya Yasui, who have been investigating plants in Ogasawara. They impressed me with their energetic works and helped me with useful suggestions about the nature in Ogasawara. I thank also to Dr.Mikio Ono, Dr.Tomomi Ito, Miss Akiko Soejima, Mr.Shoko Mishio, Dr.Sumiko Kobayashi, and Dr.Makoto Kato for their suggestions on higher plants there. Dr.Nobumitu Kawakubo and Dr.Masaki Funakoshi often stimulated me with their approaches to questions in their researches and enlightened me with their respectable devotion to field researches. Mr.Yasuhiro Suganuma, Mr.Hiroyuki Tachikawa, Mr.Hayato Chiba, Mr.Fumihiko Sato, Mr.Kaoru Hasegawa, Mr.Fuyuo Nobushima, Mr.Kiyoshi Ozawa, and Mr.Yusuke Inoue gave me valuable comments on the nature and the history in the Ogasawara Islands.

I greatly thank to the following people for helping me for various aspects of the present study. Dr.Seiki Yamane and Dr.Yuji Kishi gave me valuable suggestions and showed me their sincere attitudes to science with frank criticisms on my work. Prof.Takehiko Nakne, Prof.Hideo Tagawa, and Prof.Tadashige Habe encouraged me and gave useful comments. Prof.Junichi Aoki, Mr.Kenichi Numazawa, Mr.Shinji Koyano, Mr.Koji Takeuchi, Mr.Kenichi Kitagawa, Mr.Kunitaka Sotokawauchi, Mr.Masasi Kaneda, Mr.Kenji Totani, Dr.Satoshi Chiba, Mr.Taiji Kurozumi, and Dr.Rei Ueshima provided me with valuable comments about Achatina fulica and other species of land snails.