be by marriage with a member of the community, the new
arrival comes to occupy a definite status. Thus, in a Plains
Indian myth a young boy finds a strange girl whom he
adopts as his sister; automatically she becomes the sister of
his brothers, who accordingly are prohibited from marrying
her. In real life these implications are consistently carried
out, so that the stranger would be a daughter to her adop-
ters' parents, a sister-in-law to their wives, and so forth.
In short, she would be classified for the entire family circle
and her social relations would be regulated thereby.

It is largely the character of these kinship usages that dif-
ferentiates family life among different tribes and divides
its operations in primitive society from those of our own;
and they are so numerous and diversified that a special chap-
ter must be devoted to the matter. They involve both duties
to relatives and claims on their help and property; both
strict prohibitions as to intercourse and sanctions of ex-
travagant forms of intercourse. The systematic study of
the subject, which owes much to the energy of Dr. Rivers,
is still in its infancy; yet something of value may already
be extracted from the vast array of detail.

Certain peculiar relations with the maternal and paternal
kin must profoundly affect social intercourse. For example,
where a mother's younger sister is likely to become the
father's second wife through the sororate, the initial atti-
tude of the children towards her is bound to be influenced
by the circumstance, and vice versa. Correspondingly, the
levirate creates a bond between a father's brother and his
brother's son to which there can be nothing analogous in
civilized society. There are functions connected with other
maternal and paternal relatives equally far-reaching in their
effects.

Ethnologists describe under the heading of avunculate

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