CONTENTS. 



I. Introduction and Historical i 



II. Specimens examined 3 



III. Diagnoses of species of Cephalodlscus 4 



IV. Coenoecium 8 



V. External characters of the zooids 17 



\'I. Methods and General anatomy 21 



VII. Proboscis 26 



VIII. Collar (including the arms and the operculum) 30 



IX. Metasome, body or trunk 47 



X. Stalk 50 



XI. Alimentary canal 53 



XII. Muscular system (i(y 



XIII. Nervous system 71 



XIV. Vascular system 74 



XV. Reproductive organs Si 



XVI. Budding 91 



XVII. Development 102 



XVIII. Affinities 112 



XIX. Rhabdopleura 125 



XX. Summary of the principal results 128 



XXI. Bibliography 130 



XXII. Explanation of Plates 1 — XIV 133 



