The authors have long felt the need for a treatise on the principles andmethods of taxonomy. Such a work should be useful not only as anadjunct to teaching but also as a reference work for the practicingtaxonomist and as a source of information to the general biologist. Ananalysis and full statement of the often disputed principles on which thetaxonomic method is based are urgently needed. We share the view ofO. W. Richards (1947) that "it is less the findings of taxonomy than itsprinciples and methods which need to be taught" and understood. Webelieve that taxonomy is an important branch of biology which deals notonly with the identification and classification of natural populations butwith objectives that go well beyond these fundamental activities. [...]In attempting to bring together the more important elements ofmodern taxonomic theory and practice, we have, of necessity, selectedour materials primarily from the point of view of the student of livinganimals and have chosen illustrative examples with preference from ourmvn work. The problems of the paleontologist, microbiologist, andbotanist have been taken into consideration as far as practicable, but thematerials of these groups are often sufficiently different to require differentapproaches to the solution of taxonomic problems. Nevertheless, thereis much common ground of theory and method shared by the workers inthese diverse fields, and it is to be hoped that at some time in the not toodistant future all biological taxonomy may be viewed· as a single cohesivefield. If this book, by focusing attention on the problems of the systematiczoologist, serves as a step in that direction, one of its goals will havebeen achieved. If it also assists in stimulating a more critical evaluationof taxonomic theory and methods and in a wider dissemination of knowledgeconcerning them, the authors will feel that their labors have beenjustified. [From the Preface]