"I wonder if it was a fair trade?" he said. "We don't understand the Rhennius machine, and even the aliens aren't certain what the star-stone represents."

"It wasn't exactly a trade."

"Two of the treasures of Earth are gone and we have a couple of theirs in return. What else would you call it?"

"A link in a kula chain," I said.

"I am not familiar with the term. Tell me about it."

"The parallel struck me as I read the details of the deal we had been offered. The kula is a kind of ceremonial voyage undertaken at various times by the inhabitants of the island groups to the east of New Guinea-the Trobriand Islanders, the Papuans of Melanesia. It is a sort of double circuit, a movement in two opposite directions among the islands. The purpose is the mutual exchange of articles having no special functional value to the various tribes involved, but possessed of great cultural significance. Generally, they are body ornaments-necklaces, bracelets-bearing names and colorful histories. They move slowly about the great circuit of the islands, accompanied by their ever-growing histories, are exchanged with considerable pomp and ceremony and serve to focus cultural enthusiasm in a way that promotes a certain unity, a sense of mutual obligation and trust. Now, the general similarity to the exchange program we are entering with the aliens seems pretty obvious. The objects become both cultural hostages and emblems of honor to the trustees. By their existence, their circulation, their display, they inevitably create something of a community feeling. This is the true purpose of a kula chain, as I see it. That's why I didn't like the word ‘trade.' "

"Most interesting. None of the reports I've heard or read put it in that light-and certainly none of them compared it to the kula phenomenon. They cast it more in terms of an initiation fee for joining the galactic club, the price of admission to enjoy the benefits of trade and the exchange of ideas. That sort of thing."