map chap. XVII.), their reluctance to
protrude beyond its limits, and the restricted range and small numerical
strength of such protrusions as occur. This seems to be the conservatism
of the mature race type, which has lost some of its plasticity and shuns
or succumbs to the ordeal of adaptation to contrasted climatic
conditions, except when civilization enables it partially to neutralize
their effects.

[Illustration: PRIMITIVE INDIAN STOCKS OF SOUTH AMERICA (From Helmolt's
_History of the World_. By permission of Dodd, Mead & Co.)]

[Sidenote: Migrations in relation to zones and heat belts.]

In South America, Caribs and Arawaks showed a strictly tropical
distribution from Hayti to the southern watershed of the Amazon. The
Tupis, moving down the Parana-La Plata system, made a short excursion
beyond the Tropic of Capricorn, though not beyond the hot belt, then
turned equator-ward again along the coast.[195] In North America we find
some exceptions to the rule. For instance, though the main area of the
Athapascan stock is found in the frigid belt of Canada and Alaska, north
of the annual isotherm of 0 deg.C. (32 deg.F.) small residual fragments of
these people are scattered also along the Pacific coast of Oregon and
California, marking the old line of march of a large group which drifted
southward into Arizona, New Mexico, Texas and the northern part of
Mexico. The Shoshone stock, which originally occupied the Great Basin
and western intermontane plateau up to the borders of Canada, sent out
offshoots which developed into the ancient civilized tribes of tropical
Mexico and Central America. Both these emigrations to more southern
zones were part of the great southward trend characterizing all
movements on the Pacific side of the continent, probably from an
original ethnic port of entry near Bering Strait; and part also of the
general southward drift in search of more genial climate, which landed
the van of northern Siouan, Algonquin and Iroquoian stocks in the
present area of South Carolina, Georgia, Alabama, Mississippi and
Louisiana, while the base of their territory stretched out to its
greatest width in southern Canada and contiguous parts of the United
States. [See map page 54.][196]

[Illustration: ETHNOGRAPHICAL MAP OF INDIA FROM THE INDIAN CENSUS OF
1901.]

[Illustration: ETHNOGRAPHICAL MAP OF ASIA. Vertical Shading in the
North is Slav.]

[Sidenote: Range of movements in Asia.]

If we turn to the easter