The correlation between fecundity and longevity which Karl Pearson
has demonstrated gives longevity another great advantage as a standard
in sexual selection. See _Proc. Royal Soc. London_, Vol. 67, p. 159.

[104] It is objected that if the long-lived marry each other, the
short-lived will also marry each other and thus the race will gain no
more than it loses. The reply to this is that the short-lived will marry
in fewer numbers, as some of them die prematurely; that they will have
fewer children; and that these children in turn will tend to die young.
Thus the short-lived strains will gradually run out, while the
long-lived strains are disseminated.

[105] Hankins, F. H., "The Declining Birth-Rate," _Journal of Heredity_,
V, pp. 36-39, August, 1914.

[106] Smith, Mary Roberts, "Statistics of College and Non-college
Women," Quarterly Pubs. of the _American Statistical Assn._, VII, p. 1
ff., 1900.

[107] "Statistics of Eminent Women," _Pop. Sci. Mo._, June, 1913.

[108] "Marriage of College Women," _Century Magazine_, Oct., 1895.

[109] Blumer, J. O., in _Journal of Heredity_, VIII, p. 217, May, 1917.

[110] The statistics of this and the following middle west universities
were presented by Paul Popenoe in the _Journal of Heredity_, VIII, pp.
43-45.

[111] _Harvard Graduates' Magazine_, XXV, No. 97, pp. 25-34, September,
1916.

[112] Popenoe, Paul, "Stanford's Marriage-Rate," _Journal of Heredity_,
VIII, p. 170-173.

[113] Banker, Howard J., "Co-education and Eugenics," _Journal of
Heredity_, VIII, pp. 208-214, May, 1917.

[114] _Eugenics: Twelve University Lectures_, p. 9, New York, 1914.

[115] Cf. Gould, Miriam C., "The Psychological Influence upon Adolescent
Girls of the Knowledge of Prostitution and Venereal Disease," _Social
Hygiene_, Vol. II, pp. 191-207, April, 1916. This interesting and
important study of the reactions of 50 girls reveals that present
methods or indifference to the need of reasonable methods of teaching
sex-hygiene are responsible for "a large percentage of harmful results,
such as conditions bordering on neurasthenia, melancholia, pessimism and
sex antagonism."

[116] Gallichan, Walter M., _The Great Unmarried_, New York, 1916.

[117] Sprague, Robert J., "Education and Race Suicide," _Journal of
Heredity_, Vol. VI, pp. 158 ff., April, 1915. Many of the statistics of
women's colleges, cited in the first part of this chapter, are from Dr.
Sprague's paper.

[118] Odin calculat