The following conception is dominant in France. It is sad but true that the number of births hardly shows any excess over the number of deaths--nay, that in certain years the births are fewer than the deaths; hence it happens that the population of the other states of Europe increases much more rapidly than the population of France. It is essential that something should be done to counteract this difference, by which the position of France as one of the great Powers of Europe may ultimately be endangered. Since all the laws and regulations which have been instituted with a view to increasing the birth-rate have remained fruitless, some new method must be found of bringing about a more marked excess of births over deaths. Since excessive mortality among children is the principal cause of a high death-rate, the State and the community must take all the steps in their power to reduce child mortality to a minimum. _Fertility of the Lower Classes._--In the civilised countries of twentieth-century Europe, the mean birth-rate is about thirty; that is, for every thousand inhabitants, there are thirty births each year; France is far below this mean, with a birth-rate of twenty-one, and Russia far above, with a birth-rate of about forty-nine. In the country districts, fertility and the birth-rate are greater than in the towns. Transient variations in the birth-rate depend upon various disturbing factors, such as war, civil disorders, and rise in the prices of the necessaries of life. The lower the type of life, the greater is the insecurity of existence; and it is necessary that this should be counterbalanced by greater vigour of the forces of reproduction, and a consequent increase in the number of the offspring. Thus differences between the different species have a great influence upon the procreativeness of these species, so that there is a direct causal connection between the quality of a species and the number of the individuals of which it is made up. But it remains in dispute whether the rise (or fall) in the quantity, directly gives rise to a decline (or increase) in the quality; whether, within the limits of an individual species, the quantitative differences between the individuals making up that species are of importance; whether, within the limits of a single species, the individual members are more fertile in proportion as they stand at a lower level in development; and, finally, whether the fertility of the individuals of any species diminishes as the species advances in its evolution.