The Principles of Kinship indirect, general or special, immediate or deferred, explicit or implicit, closed or open, concrete or symbolic, it is exchange, always exchange, that emerges as the fundamental and common basis of all modalities of the institution of marriage. If these modalities can be subsumed under the general term of exogamy (for, as we have seen in Part I, endogamy is not opposed to exogamy, but presupposes it), this is conditional upon the apperception behind the superficially negative expression of the rule of exogamy, of the final principle which, through the prohibition of marriage within prohibited degrees, tends to ensure the total and continuous circulation of the group's most important assets, its wives and its daughters. The functional value of exogamy, defined in its widest sense, has been specified and brought out in the preceding chapters. This value is in the first place negative. Exogamy provides the only means of maintaining the group aa as a group, of avoiding the indefinite fission and segmentation which the practice of consanguineous marriages would bring about. If these consan guineous marriages were resorted to persistently, or even over-frequently, E they would not take long to fragment the social group into a multitude of families, forming so many closed systems or sealed monads which no pre-established harmony could prevent from proliferating or from coming into confict. The rule of exogamy, applied in its simplest forms, is not entirely sufficient to the task of warding off this mortal danger to the group B. Such is the case with dual organization. with it there is no doubt that the risk seeing a biological far mily become est stablished as a closed system is definitely eliminated; the biological group can no longer stand apart, and the bond of alliance with another family ensures the dominance of the social i. over the biological, and of the cultural over the natural. But there immediately war appears another risk, that of seeing two familie rather two lir 23. isolate themselves from the social continuum to form a bi-polar system, an indefinitely self-sufficient pair, closely united by a succession of intermarriages The rule of exogamy, which determines the modalities for forming such pairs, gives them a definite social and cultural character, but this social character is no sooner given than it is disintegrated. This is the danger which is avoided by the more complex forms of exogamy, such as the principle of generalized exchange, or the subdivision of moieties into sections and subsections in which more and more numerous local groups constitute indefinitely more complex systems. It is thus the same with women as with the currency the name of which they often bear, and which, according to the admirable native saying, ' depicts the action of the needle for sewing roots which, weaving in and out, leads backwards and forwards the same liana, holding the straw together,. Even when there are no such procedures, dual s: organization is not itself ineffective. We have seen how the intervention of preferred degrees of kinship within the moiety, e.g., the predilection for the real cross-cousin, and even for a certain type of real cross-cousin, as among 1 Leenhardt, 1930, pp. 48, 54