20
Woods, Frederick Adams, Heredity in Royalty, New York, 1906.
21
Beeton, Miss M., Yule, G.U., and Pearson, Karl, On the Correlation between Duration of Life and the Number of Offspring, Proc. R. S. London, 67 (1900), pp. 159-171. The material consisted of English and American Quaker families. Dr. Bell's work is based on old American families, and has not yet been published.