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4. B. C. Jørgensen, C. Rosenkilde, andK. G. Wingstand,Bertil Hanstrom Zoological Papers (Ed.K. G. Wingstrand; Zoological Institute, Lund, Sweden 1956), p. 184.
5. This work was supported by the Population Council of the Rockefeller Institute, New York. I am indebted to Dr.A. Gorbman, Department of Zoology, University of Washington, for providing all facilities and encouragement.