1. Department of Zoology, 421 Birge Hall, University of Wisconsin, Madison, Wisconsin 53706, USA
2. Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia V9R 5K6, Canada
3. ‡Deceased autumn 1990
4. Norwegian Polar Research Institute, PO Box 158, N‐1330 Oslo Lufthavn, Norway