In the short history of the subject, the rapidly expanding knowledge of the physical nature and processes of the deep oceans has very much determined the approach and methodology adopted in the biological study of this, the most remote and seemingly ‘difficult’ of environments for life on Earth. At the time of the pioneering voyage of the ‘Challenger’, knowledge of deep-ocean bathymetry barely existed, vast areas of ocean basins had never been sounded, and a certain sameness in the catch of larger animals trawled from the depths, as the ship worked wide-spaced stations across the ocean basins, encouraged a view of an almost endless, though impoverished, uniformity in the animal life existing on the deep-sea ooze. Such a view encouraged workers to think that it is perfectly feasible to make generalizations of deep-sea biology from single and widely spaced hauls made with the relatively crude technical gear available. As graphically illustrated by Sparck (1956a), the idea of assessing the ocean's fauna by means of a few trawl and dredge hauls is absurd in relation to its vast area and volume: fishing up a postman and a policeman from a net cast randomly from a balloon floating above land might similarly lead to a distorted picture of a human population below made up entirely of postmen and policemen!

This concept of uniformity remains valid today only in a restricted way.