Not only do the wives of the working classes produce individually more children than those of the professional classes, but, owing to these earlier marriages, generations succeed each other with greater rapidity. In order to realise how soon a slight advantage like this tells upon the composition of the race, we will suppose for the nonce that the labourer’s wife A marries at twenty-three, and the lawyer’s wife B marries at twenty-six, and that they have the same number of children, in each case four. In the case of A the population will double, say roughly, every twenty-seven years, and in the case of B every thirty years, allowing in each case four years for the birth of the family. As we shall see by the following table, the population produced by the labourer’s wife A will in 270 years be 2,048, while the population produced by the lawyer’s wife B will be half as much, namely, 1,024 in the same period.[30] ------------+------------------------------ | Years required to produce it. No. of +------------------------------ Population. | A B ------------+------------------------------ 4 | 27 30 5 | 54 60 6 | 81 90 32 | 108 120 64 | 135 150 128 | 162 180 256 | 189 210 512 | 216 240 1,024 | 243 270 2,048 | 270 300 ------------+------------------------------ As regards the men, it is also probable that those who marry at thirty will on the whole be fathers of smaller families than those who marry at twenty-five, even did they mate with women of the same age. Of this, however, I cannot adduce reliable statistical evidence. _Their Infant Mortality is Greater._ The lower classes appear, therefore, to be more fertile; they more frequently marry, and they marry at earlier and more fertile ages. On the other hand it must at once be admitted that they manage to rear a smaller percentage of their off-spring. The mortality amongst the infants and children is often alarmingly great through ignorance and neglect on the parent’s part. While, therefore, the lower classes are undoubtedly the most fertile, it is not certain how far this is counterbalanced by the lower mortality which exists among the children and youth of the upper classes. _Artificial Restriction of the Family._