The world of the eighteenth century, a historian has remarked, was a small place. Naturalists who never laid eyes on each other became intimate friends by virtue of the letters they wrote to each other""--and they saved on postage by routing them through Philadelphia's sympathetic postmaster Ben Franklin. Inspired by Linnaeus, the pantheon of naturalists who catalogued the New World in the eighteenth and early nineteenth centuries was a criterion group--talented, ardent, quirky, persevering. A few, like Audubon or Lewis and Clark, are generally familiar; several more are known from species named for them; most are obscure characters justly illumined in Kastner's skillful narrative. Domestic or imported, self-taught or formally tutored, they traipsed through wild territories or frequented fish markets, wrangled with alligators or stumbled over rare specimens, freely embellished the hardships they endured--and thoroughly enjoyed what they discovered. (""Give me a fin, and I will tell you the fish,"" boasted Samuel Mitchill, for whom striped bass--Perca mitchilli--was originally named.) When Europeans, especially the French Buffon, discounted New World species as inferior, Americans responded with biological warfare--shipping a disassembled moose to Paris, holding a dinner for thirteen (plus piano) in a mastodon's rib cage--and the search for specimens became entwined with emerging feelings of patriotism. Kastner, former Life editor, admirably recreates the trellis of relationships that supported these backyard enthusiasts and backwoods adventurers until, by the 1850s, the amateurs yielded to the professionals and the ""closet"" specialists took over. Enhanced by selected quotations from contemporary letters, journals, and books, this is a nimble, spirited expedition amplifying all those Latin names and legendary figures.