1. Marine Biological Laboratory, Woods Hole, MA 02543, U.S.A.
2. Department of Physiology, Boston University School of Medicine, Boston, MA 02118, U.S.A.
3. asic Research Laboratories, Corporate Technical Division, Chisso Corporation, Yokohama 236, Japan.
4. Department of Chemistry, Harvard University, Cambridge, MA 02138, U.S.A.