This book is written for ecologists and protozoologists. Ecologists who study environments and biotic communities in which protozoa are im portant should find this book especially useful. During the last decade it has become clear that protozoa play important roles in natural eco systems, but few ecologists have a feeling for the functional properties and the diversity of these organisms. Protozoa pose or exemplify many general problems of population and community ecology, and of evo lutionary biology. In most respects the general ecological properties of protozoa are not fundamentally different from those of larger organisms; yet, due to their small size, short generation times, and ubiquitous oc currence they often present ecological phenomena in a new and dif ferent light. To this should be added that protozoa are well-suited for experimental work. Despite these advantages, the study of protozoa has played a relatively modest role in the development of ecology and ev olutionary biology, primarily, I believe, because most ecologists are unfamiliar with these organisms. I hope this book will attract more attention to these favorable characteristics of protozoa. I also hope that this book may make protozoologists aware of new aspects of their pet organisms. For a long time (that is, until the fun damental distinction between prokaryotic and eukaryotic cells was rec ognized) protozoa were believed to represent the simplest form of life. They were therefore extensively used for the experimental study of basic questions of cell biology.

distances between groups of ciliates were as vast as significant hurdles to obtain copyright permissions the genetic distances between plants and animals for the over 1,000 required illustrations, and I put – THE major eukaryotic kingdoms at that time! the publication schedule ahead of this element. I continued to collaborate with Mitch, and in There are a number of significant illustrated guides 1991 my first “molecular” Magisterial student, to genera and species that have recently been pub- Spencer Greenwood, published an article estab- lished. References are made to these throughout lishing 1990 or thereabouts as the beginning of the book as sources that readers can consult for this the “Age of Refinement” – the period when gene aspect of ciliate diversity. A future project that I am sequencing techniques would deepen our under- contemplating is an illustrated guide to all the valid standing of the major lines of evolution within ciliate genera.