2. Race and constitution have a distinct influence upon the age at which menstruation makes its appearance. In women of the Semitic races the menarche occurs earlier than in women of the Aryan races. The average age at which menstruation begins is in Jewish girls, from 14 to 15; in Magyar girls from 15 to 16; in German girls from 16 to 16½; and in Slavonic girls from 16 to 17. In general the menarche is earlier in girls of a sanguine, lively temperament and a powerful constitution than in girls of a phlegmatic temperament and a weakly constitution; further, other things being equal, menstruation appears earlier in brunettes, girls with black hair, thick skin, dark eyes, and a dark complexion, than it appears in blondes, girls with light hair, thin skin, blue eyes, and a fair complexion. 3. The age at which menstruation begins is also affected by the conditions of life and the social circumstances. In the higher circles of society, in the upper, well-to-do classes, menstruation appears earlier than among women of the laboring classes, who are compelled to strive for their daily bread. Amongst upper-class girls the menarche occurs at the age of 14 in one-fourth of their number, whereas among lower-class girls barely one-sixth begin to menstruate at the age of 14. In large towns, again, menstruation appears earlier than in small towns, whilst in the open country the menarche is still further delayed. In the women of Paris the average age at the menarche is 14 years and 6 months, in the women of smaller French towns it is 14 years and 9 months, in French countrywomen it is 14 years and 10 months. How far the mode of nutrition is concerned in the production of these results is not yet determined. 4. The time of the menarche appears to be influenced by inheritance to this extent, that the daughters of women who began to menstruate early begin themselves to menstruate at an early age, whereas in other families we observe that both mothers and daughters began to menstruate late. But this relation is by no means a constant one. _Ploss_ has collected observations made in various countries and towns regarding the age at which menstruation begins, and the mean results of these observations are given below. The average age at which menstruation began was: