Those who wish to pursue the subject further will find in the ‘Voyages of the “Blake,”’ by Alexander Agassiz, an excellent and elaborate discussion of deep-sea problems, and numerous illustrations of some of the most interesting forms of abysmal life. In Volume XXIII. of the ‘Bulletin of Comparative Zoology’ the same author gives a most interesting account of the deep-sea work that has recently been done by the ‘Albatross’ expedition. Filhol’s ‘La Vie au Fond des Mers’ is also a book that contains a great deal of new and interesting matter, together with some excellent coloured plates of deep-sea animals. SYDNEY J. HICKSON. DOWNING COLLEGE, CAMBRIDGE: _September, 1893_. CONTENTS CHAPTER PAGE I. A SHORT HISTORY OF THE INVESTIGATIONS 1 II. THE PHYSICAL CONDITIONS OF THE ABYSS 17 III. THE RELATIONS OF THE ABYSMAL ZONE AND THE ORIGIN OF ITS FAUNA 45 IV. THE CHARACTERS OF THE DEEP-SEA FAUNA 59 V. THE PROTOZOA, CŒLENTERA, AND ECHINODERMA OF THE DEEP SEA 86 VI. THE VERMES AND MOLLUSCA OF THE DEEP SEA 109 VII. THE ARTHROPODA OF THE DEEP SEA 123 VIII. THE FISH OF THE DEEP SEA 148 INDEX 167 LIST OF ILLUSTRATIONS STOMIAS BOA. AFTER FILHOL, ‘LA VIE AU FOND DES MERS’ _Frontispiece_ FIG. PAGE 1 DIAGRAM ILLUSTRATING THE PASSAGE OF AN OCEAN CURRENT ACROSS A BARRIER 32 2 _Sicyonis crassa._ AFTER HERTWIG, ‘“CHALLENGER” REPORTS’ 36 3 GLOBIGERINA OOZE. AFTER AGASSIZ, ‘VOYAGES OF THE “BLAKE”’ 38 4 SECTION THROUGH THE EYE OF _Serolis schythei_. AFTER BEDDARD, ‘“CHALLENGER” REPORTS’ 74 5 SECTION THROUGH THE EYE OF _Serolis bromleyana_. AFTER BEDDARD, ‘“CHALLENGER” REPORTS’ 74 6 _Opostomias micripnus._ AFTER GÜNTHER, ‘“CHALLENGER” REPORTS’ 78 7 HEAD OF _Pachystomias microdon_. AFTER VON LENDENFELD, ‘“CHALLENGER” REPORTS’ 79 8 SECTION THROUGH THE ANTERIOR SUB-ORBITAL PHOSPHORESCENT ORGAN OF _Pachystomias microdon_. AFTER VON LENDENFELD, ‘“CHALLENGER” REPORTS’ 80