is fallacious. The way fertility is calculated is to divide the number of births in a given year by the number of marriages contracted during the same year. Only very few of the births during any one year are due to the marriages during that year, but are from couples married within the preceding twenty-five years. If the number of mixed marriages did not increase, such a division would more or less accurately give us the average fecundity. But as has been shown above, the number of mixed marriages increases regularly in every country considered, so that the births of the year considered represent the fecundity of a smaller number of marriages than have been contracted during this year. A smaller fertility is thus apparently seen among the mixed marriages. I will illustrate this by figures obtained by Ruppin about conditions in Prussia: During 1901 there were 4.2 births to each christian marriage; 2.80 to each Jewish marriage; and only 1.80 to each marriage of a christian to a Jewess and 1.53 to each marriage of a Jew with a christian woman. But recalling that only a few of these births were the results of marriages contracted during 1901, but represent marriages for about twenty-five years, we are led to investigate further. In 1876 only 256 mixed marriages were contracted in Prussia, and during the twenty-five succeeding years they increased annually, reaching 455 in 1901. If we accordingly calculate the birth rate for 1901 on the basis of the average number of marriages during these twenty-five years (1876-1901), the result is entirely different. Ruppin shows that the rates calculated by this method are 5.07 births to each christian marriage, 2.96 to each Jewish marriage, 2.5 to each marriage of a christian with a Jewess and 2.35 to each marriage of a Jew with a christian woman. The difference is thus not much in favor of pure Jewish marriages when compared with mixed. But even this does not give us a clear picture, because in many mixed marriages one of the parties accepts the religion of the other, and the births are then recorded not as the issue of a mixed marriage, but of a pure christian or pure Jewish marriage, as the case may be. Many births resulting from mixed marriages are consequently missing from the official records, thus reducing the average number of births perceptibly. Considering this and, in addition, the fact that most of the mixed marriages occur in large cities, where the birth rates are much lower than in the country, one is bound to agree with Ruppin that the Prussian official statistics do not support the theory that mixed marriages are less fertile than pure manages.
There is very little to be said about the alleged physical deterioration of the offspring of mixed marriages, because it has not been proved
