It is surprising, given the current surge of activities in the history of biology, that little attention has been paid to the development of our understanding of protozoa and associated organisms. The province of protozoa, reminiscent of the fertile crescent in the Middle East, straddles the highways of thought that run between the major continents of biology. Down these roads come caravans of concepts and analogies: ideas about hierarchies and taxonomies from one direction, convictions about the basic structures and functions of life from another, opinions about reproduction and development from a third, and theories of the origin and evolution of life's forms from still another quarter. It is uncanny how these separate trains of thought intersect one another in the land of single-celled organisms. There they interact, exchange views, and rearrange their loads before they disperse again to inform other regions of biology of their contents and conclusions. A complete history of protozoology must recognize the centrality of this terrain.
There exist classic science texts that detail some events in this history, and some of the best, such as Otto Bfitschli's massive volume on Protozoa in Heinrich Bronn's Klassen und Ordnungen des Thierreiches (1880--1889) and William Saville Kent's Manual of the Infusoria (1880), provide historical overviews of the primary literature and hints that there is a good deal more going on in the discipline than simply the coinage of nomenclature and an accumulation of facts. Francis Joseph Cole's History of Protozoology (1926), written a generation later, is a scant volume which concentrates on the chronology of events. In the past decade John O. Corliss has kept this tradition alive in a number of informative contributions. All of these accounts, invaluable from a factual standpoint, were written in the spirit of biologist-turnedhistorian. Out of necessity and inclination, the questions these and other biologists ask are different from what a historian of science might address.