[97] Diffloth, Paul, _Le Fin de L'Enigme_, Paris, 1907. [98] The best popular yet scientific treatment of the subject we have seen is _The Dynamic of Manhood_, a book recently written by Luther H. Gulick for the Young Men's Christian Association (New York, The Association Press, 1917). [99] The sympathy which we mentioned as the beginning of the hypothetical love affair does lead to a partial identity of will, it is true; but there is often too little in common between the man and woman to make this identity at all complete. As Karl Pearson points out, it is almost essential to a successful marriage that two people have sympathy with each other's aims and a considerable degree of similarity in habits. If such a bond is lacking, the bond of sympathy aroused by some trivial circumstance will not be sufficient to keep the marriage from shipwreck. The occasional altruism of young men who marry inferior girls because they "feel sorry for them" is not praiseworthy. [100] Ellis, Havelock, _The Task of Social Hygiene_, pp. 208-209, Boston, Houghton Mifflin Co., 1912. [101] G. Stanley Hall (_Adolescence_, II, 113) found the following points, in order, specified as most admired in the other sex by young men and women in their teens: eyes, hair, stature and size, feet, eyebrows, complexion, cheeks, form of head, throat, ears, chin, hands, neck, nose. The voice was highly specialized and much preferred. The principal dislikes, in order, were: prominent or deep-set eyes, fullness of neck, ears that stand out, eyebrows that meet, broad and long feet, high cheek-bones, light eyes, large nose, small stature, long neck or teeth, bushy brows, pimples, red hair. An interesting study of some of the trivial traits of manner which may be handicaps in sexual selection is published by Iva Lowther Peters in the _Pedagogical Seminary_, XXIII, No. 4, pp. 550-570, Dec., 1916. [102] It has been suggested that the same goal would be reached if a young man before marriage would take out a life insurance policy in the name of his bride. The suggestion has many good points. [103] 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.