1. Experimental Animal Research Laboratory, Meiji University, Tama-ku, Kawasaki, Kanagawa 214, Japan
2. Zoological Institute, Faculty of Science, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan
3. Department of Endocrinology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113, Japan
4. Laboratory of Animal Breeding, College of Agriculture and Veterinary Medicine, Nihon University, Kameino, Fujisawa, Kanagawa 252, Japan