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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.—Representative 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: Pressure, Temperature, and Absence of Light.
The sea covers nearly three-fourths of the surface of the 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 utter darkness, subjected to such stupendous pressure as to make life of any kind impossible, and to throw insuperable diffi-
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