CONTENTS. 



CHAPTER I. 



INTRODUCTION. 



The Question of a Bathymetrical Limit to Life.— The general Laws which 

 regulate the Geographical Distribution of Living Beings.— Professor 

 Edward Forbes' Investigations and Views.— Specific Centres.— Repre- 

 sentative Species.— Zoological Provinces. — Bearings of a Doctrine of 

 Evolution upon the Idea of a ' Species,' and of the Laws of Distribution. 

 — The Circumstances most likely to affect Life at great Depths : Pres- 

 sure, Temperature, and Absence of Light Page 1 



CHAPTER II. 



THE CRUISE OF THE 'LIGHTNING.' 



Proposal to investigate the Conditions of the Bottom of the Sea. — Sugges- 

 tions and Anticipations. — Correspondence between the Council of the 

 Royal Society and the Admiralty. — Departure from Stornoway. — The 

 Fieroe Islands. — Singular Temperature Results in the Fteroe Channel. — 

 Life abundant at all Depths. — Brisinga coronata. — Holtenia carpenteri. 

 —General Results of the Expedition Page 49 



Appendix A. — Particulars of Depth, Temperature, and Position at the 

 various Dredging Stations of H.M.S. 'Lightning,' in the Summer of 

 1868 ; the Temperatures corrected for Pressure Page 81 



CHAPTER III. 



THE CRUISES OF THE ' PORCUPINE.' 



The Equipment of the Vessel.— The first Cruise, under the direction of Mr. 

 Gwyn Jeffreys, off the West Coast of Ireland and in the Channel 

 between Scotland and Rockall.— Dredging carried down to 1,470 fathoms. 



