a limit. This cannot go on without end.

[Illustration: FIG. 1.--INCREASE OF POPULATION IN THE
UNITED STATES AND THE PRINCIPAL COUNTRIES OF EUROPE
FROM 1800 TO 1900 (From "Statistical Atlas," Twelfth
Census of the United States.)]

An extremely pertinent fact here has been disclosed by Pearson and is
based upon very extensive observations among several different classes
and nations. It is this--that one fourth of the married population of
the present generation produce one half of the next generation. The
death rate and the ratio of unmarried to married being what they are,
this relation may be stated in this way--twelve per cent of all the
individuals born in the last generation produced one half of the
present generation. "This is not only a general law, but it is
practically true for each class in the community." This conclusion is
based upon data from the English, Danish, and Welsh peoples of
professional, domestic, commercial, industrial, and pastoral classes,
and the per cent of married persons found to be producing one half of
each generation varies from twenty-three to twenty-seven with an
average of twenty-five per cent. We must ask at once--what is the
source of this fourth which is contributing double its quota to the
next generation? Is this twenty-five per cent drawn proportionately
from all classes of society or are some groups contributing
relatively more than others? Is there any relation between this
superfertility and the possession of desirable or undesirable
characteristics? We may answer at once--there is a distinct and
positive relation between civic undesirability and high fertility. We
shall return to this subject at the close of the next chapter; only
the bare fact is to be mentioned at this time.

It is a matter of common notice and remark that to-day, in England at
any rate, there is a dearth of youthful ability. It exists in
commerce, science, literature, politics, the bar, the church. We
cannot dismiss as merely fashionable the statements that the able
classes are not replacing themselves, that men of ability are less
able than formerly. Whether or not this is also the condition in
America to-day, we know that it soon will be the condition unless
steps are taken to bring about a positive relation between civic
desirability and ability and the numerical production of offspring.

Let us turn to data of a somewhat different kind. The United States
Census Reports for the de