Disregarding the last class altogether, it is yet evident that while the mother in a wealthy home bears two children, the mother in the slums bears four. It is evident then that in Paris at the present time reproductive selection is changing the mental and moral composition of the population at a rapid rate, which can not be very materially reduced even if it is found that the death-rate in the poorer districts is considerably greater than it is on the more fashionable boulevards.
J. Bertillon has brought together16 in a similar way data from a number of cities, showing the following birth-rates:
| Berlin | Vienna | London | |
|---|---|---|---|
| Very poor quarters | 157 | 200 | 147 |
| Poor quarters | 129 | 164 | 140 |
| Comfortable quarters | 114 | 155 | 107 |
| Very comfortable | 96 | 153 | 107 |
| Rich | 63 | 107 | 87 |
| Very rich | 47 | 81 | 63 |
| — | — | — | |
| Average | 102 | 153 | 109 |
Obviously, in all these cases reproductive selection will soon bring about such a change in the character of the population, that a much larger part of it than at present will have the hereditary characteristics of the poorer classes and a much smaller part of it than at present the hereditary characteristics of the well-to-do classes.
David Heron and others have recently studied17 the relation which the birth-rate in different boroughs of London bears to their social and economic conditions. Using the correlation method, they found "that in