What is the motive force behind these obligations? The coastal and inland villages respectively have to reply upon each other for the supply of food. On the coast the natives never have enough vegetable food, while inland the people are always in need of fish. Moreover, custom will have it that on the coast all the big ceremonial displays and distributions of food, which fonn an extremely important aspect of the public life of these natives, must be made with certain specially large and fine varieties of vegetable food, which grow only on the fertile plains inland. There, on the other hand, the proper substance for a distribution and feast is fish. Thus to all other reasons of value of the respectively rarer food, there is added an artificially, culturally created dependence of the two districts upon one another. So that on the whole each community is very much in need of its partners. If at any time previously these have been guilty of neglect, however, they know that they will be in one way or another severely penalized. Each community has, therefore, a weapon for the enforcement of its rights: reciprocity.