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The results of recent deep-sea exploration have been summarized by Mr. Sydney J. Hickson, Fellow of Downing College, Cambridge, in a short work on The Fauna of the Deep Sea, published in the “Modern Science Series.”^[1] Though the bulk and specialized character of the reports of separate expeditions organized by the English, French, German, Italian, and Norwegian governments, makes such a task one of no ordinary difficulty, Mr. Hickson has succeeded in his wish to “give in a small compass the more important facts of this great mass of literature in such a form as may interest those who do not possess a specialist’s knowledge.” The main conclusions are clearly presented with examples and excellent illustrations, in number sufficient to convince without bewildering. On one point we could desire a little more information. There is no suggestion of the means by which creatures differing so little in bodily frame and tissue from the shallow-water species, from which they are apparently derived by migration into the deeps, support the enormous pressure in their present home. Some explanation seems to be required, though an incident in the recent erection of the Forth Bridge seems to suggest that the modification of tissue to endure high pressure may be acquired more rapidly than is supposed. The men employed in the steel shells or caissons sunk to form the foundations of the piers, worked in a pressure of air rather greater than the pressure of the water outside, which would otherwise have penetrated between the rims of the caissons and the ground. On those days on which they were not employed, and came to the surface, they felt such pain in the joints from the expansion of the air, which had been absorbed at high pressure, that they begged to be allowed to go down into the caissons and spend their off hours in the pressure to which they had grown accustomed. This instance of partial migration into conditions of high pressure, seems worthy of a place among the facts of deep-sea exploration. Yet it must remain among the strangest features of life in the ocean abyss, that its inhabitants show so little visible change of structure to meet what seems the first and most overwhelming change of physical conditions. The angler-fish and eels, crabs and prawns, star-fish and zoophytes of the shallow waters are represented in the abyss by forms almost similar in structure, though that some difference must exist is shown by the fact that when brought up by the dredge from the depths of the ocean they are killed and distorted by the diminution and disappearance of the vast pressure in which they habitually live. “The fish which live at these enormous depths,” writes Mr. Hickson, “are liable to a curious form of accident. If, in chasing their prey, or for any other reason, they rise to a considerable distance above the floor of the ocean, the gases of their swimming-bladder become greatly expanded, and their specific gravity reduced. If the muscles are not strong enough to drive the body downwards, the fish, becoming more and more distended as it goes, is gradually killed on its long and involuntary journey to the surface of the sea. The deep-sea fish, then, are exposed to a danger that no other animals in this world are subject to—namely, that of tumbling upwards.”