1. The Population Council (E.T.S., J.C.H.L., J.G., C.Y.C.), New York, New York 10021
2. the Department of Zoology, University of Hong Kong (E.T.S., J.C.H.L., W.M.L.), Hong Kong, People’s Republic of China
3. the Department of Pharmacology of Natural Substances and General Physiology, University of Rome La Sapienza (B.S.), Rome 00185, Italy