The figures of new species of Radiolaria (about 1600 in number) which appear in the atlas of one hundred and forty plates accompanying this Report, were nearly all drawn with the camera lucida, partly by Mr. Adolph Giltsch and partly by myself. The names of the genera which appear at the bottom of the plates have in many cases been changed since they were printed off, as may be seen from the explanations which accompany them. Had it been possible to complete the examination of the material before the plates were commenced this might have been avoided, and in many cases a better selection of figures might have been made. All the drawings have been made upon the stone by the practised hand of Mr. Adolph Giltsch, in his usual masterly manner, and his lithographic work, which has lasted fully ten years, is the more valuable since he has himself microscopically studied the greater part of the species figured. The fact that the atlas presents so full a picture of the marvellous wealth of form of the Radiolaria is especially due to his lively interest in the work, to his unwearying care, and to his morphological acuteness. May it be the means of inducing many naturalists to study more deeply this inexhaustible kingdom of microscopic life, whose endless variety of wonderful forms justifies the saying--_Natura in minimis maxima_. CONTENTS. FIRST PART. GENERAL INTRODUCTION-- PAGE I. Anatomical Section (§§ 1-140), i Chapter I. The Unicellular Organism, i " II. The Central Capsule, xxiv " III. The Extracapsulum, li " IV. The Skeleton, lxviii II. Biogenetical Section (§§ 141-200), xciii Chapter V. Ontogeny (Individual Development), xciii " VI. Phylogeny (Genealogical Development), ci III. Physiological Section (§§ 201-225), cxxviii Chapter VII. Vegetative Functions, cxxviii " VIII. Animal Functions, cxl IV. Chorological Section (§§ 226-250), cxlvi Chapter IX. Geographical Distribution, cxlvi " X. Geological Distribution, clxiv V. Bibliographical Section (§§ 251-254), clxxvi SYSTEMATIC PART, 1