Amazonia: a region nearly as large as the continental United States with at least 100 Indian villages in which no outsider has ever set foot; fires the size of Belgium uncontrollably clearing the land for development; so many species of birds, plants, fish that no scientist can even guess the number still to be described. Alex Shoumatoff, a Washington Post reporter turned full-time naturalist, lost himself for nearly a year in all this vastness. He explains what he found in a travelogue narrative whose intimate tone recalls the great 19th-century explorer-naturalists Spruce, Wallace, and Bates, Ethnobotany appears to be his area of expertise. Though hymen may get entangled in the descriptions of plants used as contraceptives by the Menkranoti, they'll enjoy the sections on the remote and friendly Menkranoti themselves. Shoumatoff confesses several times that he was out to find ""the natural man"" living as ""an integral part of nature""; but he's not ashamed to admit that the jungle drove him crazy after a while or that the Indians' fondness for begging, spitting, and nagging got on his nerves. In civilized Amazonia, he details the ecological nightmare of development but allows a no-nonsense South African developer to speak: ""This is frontier. You forge ahead and pick up the pieces afterwards."" Then again he Huck Finns it down the river with two native guides. The shifting of gears gets a little dizzying and the non-naturalist might prefer less primatology and more backbone to the rather impressionistic accounts of the Indians (their tribal organization, myths, rituals, history are only glanced at). Still, Shoumatoff compensates for patchiness with sheer buoyancy. His mixture of scientific documentation and personal quest will please a spectrum of tastes.