POPULATION AND ENVIRONMENT.—Dr. S. M. Shirokogoroff has published, through Messrs. Edward Evans and Sons of Shanghai, under the title “Ethnical Unit and Milieu,” a valuable study of population problems, in which he lays down a number of pro-positions supported by examples drawn mainly from his studies of the peoples of north-eastern Asia. In a community, if an increase of population exceeds the possibility of nourishment, the excess of population must perish or the natality must be regulated by some means, medical, artificial, social, etc. Increase of population is regulated by the extent of territory and by the growth of culture; the more intensive the exploitation of territory, the larger the population it may nourish, as, for example, in an agricultural as contrasted with a hunting community. Maintenance of the level of numerical value must be understood relatively to the variation of culture and territory, a conclusion which has a direct bearing upon the question of degeneracy and decline of any given people. Variation of some aspects of the cultural complex is followed by variation in the whole complex and entails a period of cultural disequilibrium. Physical degeneracy may be either a process of extinction or a substitution of one anthropological type for another; in both cases there is an ethnical disequilibrium. Limitations being imposed upon the possibility of variation in the factors of culture, territory and density of population, which are interdependent, the general conclusion follows that there will be a degeneration or decline and an end of the present species of man. It is probable that the greater part of the way to absolute density of population is already covered, and that mankind is at present near its culmination.