THE DEPTHS OF THE SEA. 



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. — Eepresentative Species. — Zoological Provinces. — Bear- 

 ings 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 : Pressui'e, Temperature, and Absence 

 of Light. 



The sea covers nearly three-fourtlis of tlie surface of 

 tlie earth, and, until within the last few years, very 

 little was known with anything like certainty about 

 its depths, whether in their physical or their biological 

 relations. The popular notion was, that after arriving 

 at a certain depth the conditions became so peculiar, 

 so entirely different from those of any portion of the 

 earth to which we have access, as to preclude any 

 other idea than that of a waste of uitter darkness, sub- 

 jected to such stupendous pressure as to make life of 

 any kind impossible, and to throw insuperable diffi- 

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