mily of
those who did marry was less than two children. At Bryn Mawr only 43 per
cent, married, and had 0.84 children each; the average family per
graduate was therefore 0.37. If it be objected that new immigrants and
their children are healthy and vigorous in America, it may be truly
answered that the effects of an unfavourable climate are manifested
fully only in the third and later generations. The argument may be
further supported by the fate of black men who try to settle in Europe.
Their strongly pigmented skin, which seems to protect them from the
actinic rays of the tropical sun, so noxious to Europeans, and their
broad nostrils, which inhale a larger number of tubercle bacilli than
the narrow nose-slits of the Northerner, are disadvantages in a
temperate climate. In any case, of the many thousands of negro servants
who lived in England in the eighteenth century, it would be difficult to
find a single descendant.

But there are other factors in the problem which should make us beware
of hasty generalisations. It is obvious that since the American Republic
contains many climates in its vast area, there may be parts of it which
are perfectly healthy for Anglo-Saxons, and other parts where they
cannot live without degenerating. Very few athletes, we are told, come
from south of the fortieth parallel of latitude. But the decline in the
birth-rate is most marked in the older colonies, the New England States,
where for a long period the English colonists, living mainly on the
land, not only throve and developed a singularly virile type of
humanity, but multiplied with almost unexampled rapidity. The same is
true not only of the French Canadian farmers, but of the South African
Boers, who rear enormous families in a climate very different from that
of Holland. The inference is that Europeans living on the land may
flourish in any tolerably healthy climate which is not tropical.

There are, in fact, two other causes besides climate which may prevent
immigrants from multiplying in a new country. The first of these is the
presence of microbic diseases to which the old inhabitants are wholly or
partially immune, but which find a virgin soil in the bodies of the
newcomers. The strongest example is the West Coast of Africa, of which
Miss Mary Kingsley writes: 'Yet remember, before you elect to cast your
lot with the West Coasters, that 85 per cent, of them die of fever, or
return home with their health permanently wrecked.