FECUNDAL AND INSTITUTIONAL SELECTION. 207 
Another result from the combined action of these two laws is that, 
an species well adjusted to the environment, the typical, that is the average, 
jorm of the species 1s not only the best adapted, but it ts the most fertile; 
" and this correlation between fertility and adaptation in the average 
form of the species or race is a strongly conservative principle, tending 
to prevent the rapid transformation of the race or species. Giants, 
dwarfs, and extreme departures from the type of other kinds are more 
likely to be sterile than the typical form of the species; and therefore 
if, through change in the environment or in the social conditions, some 
extreme form has an advantage in gaining subsistence, it will usually 
fail of propagating its kind with the relative rapidity of the less-favored 
averageform. Thisisat present true of highly intellectual variations 
of civilized man. ‘Those of moderate capacities are more prolific and 
accordingly persist, though less successful in other respects than the 
intellectual. But so long asthe most successful individuals are those 
surpassing the average in intellectual endowment, so long will the aver- 
age endowment be more or less steadily advancing; for, of intellectual 
families, those that are fairly fertile will leave more impress on succeed- 
ing generations than those that are sterile; and of fertile families, those 
that are above the average in intellect will have the advantage in leav- 
ing descendants to inherit their endowments. 
(16) Institutional selection is a form of exclusive breeding closely re- 
lated to social selection, but differing from it very much as artificial 
selection differs from natural selection. Institutional selection is 
the influence of institutions, customs, and laws in determining what 
classes of individuals have an opportunity to raise children. In most 
civilized countries criminals convicted of important offenses are 
usually so confined as to prevent theiradding tothe population of the 
community during the time of their confinement. This is a method 
of improving the race that might be carried farther than it has been. 
In some countries the insane, the imbecile, and lepers are confined in 
asylums and not allowed to marry, and in other countries eccle- 
siastical and military restrictions prevent certain portions of the 
community from raising families. 
(17) * Prudential selection is due to the delay of marriage and other methods 
of limiting the number of children for prudential reasons. 
(18) Result of the foregoing survey of selectional intenston.—The analy- 
sis we have now completed shows us that certain changes in the form 
of selection are due to changes in the environment and that others are 
*As section (17) does not occur in the original paper, it is printed in different 
form. 
