Transcriber's note: Text enclosed by underscores is in italics (_italics_). A single underscore introduces a subscript (CO_2), and a caret a superscript (B^1). Page numbers enclosed by curly braces (for example: {25}) have been incorporated to facilitate the use of the Alphabetical Index and other page references in the text. * * * * * THE CAMBRIDGE NATURAL HISTORY EDITED BY S. F. HARMER, Sc.D., F.R.S., Fellow of King's College, Cambridge; Superintendent of the University Museum of Zoology AND A. E. SHIPLEY, M.A., F.R.S., Fellow of Christ's College, Cambridge; University Lecturer on the Morphology of Invertebrates VOLUME VII [Illustration] HEMICHORDATA By S. F. HARMER, SC.D., F.R.S., Fellow of King's College, Cambridge. ASCIDIANS AND AMPHIOXUS By W. A. HERDMAN, D.SC. (Edinb.), F.R.S., Professor of Natural History in the University of Liverpool. FISHES (Exclusive of the Systematic Account of Teleostei) By T. W. BRIDGE, SC.D., F.R.S., Trinity College, Cambridge; Mason Professor of Zoology and Comparative Anatomy in the University of Birmingham. FISHES (Systematic Account of Teleostei) By G. A. BOULENGER, F.R.S., of the British Museum (Natural History). London MACMILLAN AND CO., Limited NEW YORK: THE MACMILLAN COMPANY 1904 _All rights reserved_ _Third Fisherman_.—Master, I marvel how the fishes live in the sea. _First Fisherman_.—Why, as men do a-land,—the great ones eat up the little ones. _Pericles_, Act II. Scene i. {v}PREFACE Owing to unforeseen circumstances, not unconnected with the foundation of a new University, the publication of this volume has been unduly delayed. Some parts of the work have actually been in type for more than four years; and although the authors have made every effort to keep them up to date, the arrangement is naturally not quite what it might have been if the articles had been written immediately before publication. In view of the novelty of Mr. Boulenger's classification of the Teleosteans, and of the fact that several independent workers have been occupying themselves with the subject during the last year or two, it is fair to state that this part of the volume was completed in 1902. Professor Herdman's account of the Ascidians was ready for publication two years earlier. Professor Bridge wishes to express his best thanks to Dr. R. H. Traquair. F.R.S., for his kindness in reading the proofs of the pages which deal with the fossil Crossopterygii, Chondrostei, Holostei and Dipnoi, and for much helpful advice and criticism; to Mr. G. A. Boulenger, F.R.S., for his valuable and suggestive criticism on certain points; and to Mr. Edwin Wilson, for the care which he has taken in the preparation of the figures. _July 1904_. {vii}CONTENTS PAGE PREFACE v