o the extent we have indicated solely in order to prevent him
from marrying his daughter, when the simple prohibition to marry her
would, so far as we can see, have been equally effective.

Dr Durkheim has suggested that phratries and classes originated
together.

If we start with two exogamous local groups in which the determinant
spouse removes, the result is two groups in which both phratries are
found, as is evident from the following graphic representation. The two
sides represent the local grouping, the letters A and B the phratry
names, and m or f male or female; the = denotes marriage, the vertical
lines show the children, the brackets show that the person whose symbol
is bracketed removes, and the italics that the symbol in question is
that of a spouse introduced from without.

mA=_fB_ mB=fA
_______| |_______
| | | |
[fB] mB=_fA_ _fB_=mA [mB]
_________| |_________
| | | |
[fA] mA=_fB_ _fA_=mB [fB]
_________| |_________
| | | |
[fB] mB=_fA_ _fB_=mA [fA]
etc. etc.

We see from this that the alternate generations are in each group A and
B, whose spouses are in the same alternation B and A, the male remaining
in the group, the female removing in each case, if we assume that the
matrilineal kinship is the rule. The permanent members of each group
therefore, and in like manner the imported members, are by alternate
generations A and B, though of course there is no difference of age
actually corresponding to the difference of generation.

By the simple phratry law that A can only marry B, and may marry any B,
local group mates are marriageable. The law however which forbids the
marriage of phratry mates is on Mr Lang's original theory founded on the
prohibition to marry group mates. If we suppose that the primal law or
the memory of it continued to work, we have at once a sufficient
explanation of the origin of the four-class system. The tribes or
nations in which the instinct against intra-group marriage was strong
enough to persist as an active principle after the law against
intra-phratry marriage had become recogn