S. T. Darling 
233 
well as Necalor this will suggest their having come to this continent by way 
of the sea from those countries in Asia where A . duodenale and Necalor are found 
to be infecting the natives, i.e. Japan and China. - 
A careful hookworm survey of existing Indian tribes may disclose the 
presence of more than one primitive stock. In other words: (a) a stock free 
from hookworms derived from Asiatic trans-Behring ancestors, (b) a stock 
harbouring both A. duodenale and Necalor derived from Asiatic trans-Pacific 
ancestors, and (c) a stock with a pure Necalor infection derived from Poly¬ 
nesian or Indonesian trans-Pacific ancestors. 
If the Indian races or some of them living in regions unvisited by strangers 
are found to be free from hookworms this would furnish some grounds for 
supposing that the races in question had been derived from ancestors who 
had crossed from Asia by way of Behring Straits. 
Surveys of all ethnic groups of people are urgently required before there 
occurs that mixing of stocks which will efface the individualities of species 
formulas. 
Surveys are particularly desired in America among various North, South 
and Central American tribes, in Asia (subtropical), the Philippines, in 
Melanesia, Micronesia, Polynesia, Australia and in Madagascar and Easter 
Island. 
