374 | ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
LACK, D. 
1954. The natural regulation of animal numbers. Oxford. 
MULLER, H. J. 
1950. Our load of mutations. Amer. Journ. Human Gen., vol. 2, pp. 111-176. 
Oszorn, F. 
1951. Preface to eugenics. 2d ed. New York. 
SCHMALHAUSEN, I. 
1949. Factors of evolution: the theory of stabilizing selection. Philadelphia. 
THopay, J. M. 
1953. Components of fitness. Symposia of the Society for Experimental 
Biology, vol. 7, pp. 96-118. 
Reprints of the various articles in this Report may be obtained, as long as 
the supply lasts, on request addressed to the Editorial and Publications 
Division, Smithsonian Institution, Washington 25, D.C. 
