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 I [Illustration] PROTOZOA By MARCUS HARTOG, M.A., Trinity College (D.Sc. Lond.), Professor of Natural History in the Queen's College, Cork PORIFERA (SPONGES) By IGERNA B. J. SOLLAS, B.Sc. (Lond.), Lecturer on Zoology at Newnham College, Cambridge COELENTERATA & CTENOPHORA By S. J. HICKSON, M.A., F.R.S., formerly Fellow and now Honorary Fellow of Downing College, Cambridge; Beyer Professor of Zoology in the Victoria University of Manchester ECHINODERMATA By E. W. MACBRIDE, M.A., F.R.S., formerly Fellow of St. John's College, Cambridge; Professor of Zoology in McGill University, Montreal London MACMILLAN AND CO., LIMITED NEW YORK: THE MACMILLAN COMPANY 1906 _All rights reserved_ And pitch down his basket before us, All trembling alive With pink and grey jellies, your sea-fruit; You touch the strange lumps, And mouths gape there, eyes open, all manner Of horns and of humps. BROWNING, _The Englishman in Italy_ CONTENTS PAGE SCHEME OF THE CLASSIFICATION ADOPTED IN THIS BOOK ix PROTOZOA CHAPTER I PROTOZOA—INTRODUCTION—FUNCTIONS OF PROTOPLASM—CELL-DIVISION—ANIMALS AND PLANTS 3 CHAPTER II PROTOZOA (_CONTINUED_): SPONTANEOUS GENERATION—CHARACTERS OF PROTOZOA—CLASSIFICATION 42 CHAPTER III PROTOZOA (_CONTINUED_): SARCODINA 51 CHAPTER IV PROTOZOA (_CONTINUED_): SPOROZOA 94 CHAPTER V PROTOZOA (_CONTINUED_): FLAGELLATA 109 CHAPTER VI PROTOZOA (_CONTINUED_): INFUSORIA (CILIATA AND SUCTORIA) 136 PORIFERA (SPONGES) CHAPTER VII PORIFERA (SPONGES)—INTRODUCTION—HISTORY—DESCRIPTION OF _HALICHONDRIA PANICEA_ AS AN EXAMPLE OF BRITISH MARINE SPONGES AND OF _EPHYDATIA FLUVIATILIS_ FROM FRESH WATER—DEFINITION—POSITION IN THE ANIMAL KINGDOM 165 CHAPTER VIII