1. Laboratory of Sensory Physiology, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
2. Department of Physiology, Boston University School of Medicine, Boston, Massachusetts 02118
3. Department of Zoology, University College, Dublin, Ireland
4. Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138
5. Laboratory of Biophysics, National Institute of Neurological and Communicative Disorders and Stroke at the Marine Biological Laboratory, Woods Hole, Massachusetts 02543