Chapter Ii. Reference Has Been Made to the Remarkable Lure At the End

of the tentacle of the Angler-fish. In the Angler of the great depths this is also found, but in the obscurity of their surroundings a lure, such as that of the shore species, would be useless, and it is actually replaced by an organ which is supposed to be phosphorescent. The mouth is enormous and armed with ferocious-looking teeth, the body is rounded and adapted for burrowing in the ooze, and we can well frame in our minds a picture of the little Fishes and other creatures attracted by the “will-o’-the-wisp” light, meeting with a sudden death in the cavernous jaws of this voracious deep-sea Fish.

It is possible that in addition to the light given off by definite organs, the slime secreted by the skin either over the whole surface or certain circumscribed regions, may be phosphorescent, but how far this may serve as a means of illumination must remain a matter of conjecture. The Crustaceans are in some cases known to emit a phosphorescent fluid. The naturalists of H.M.S. Investigator found a brilliantly phosphorescent liquid in the glands at the base of the antennæ and elsewhere in certain deep-sea Shrimps, and one of the Cray-fish from great depths is said to have two definite spots on the body that emit a phosphorescent light.

Several of the Star-fish and Brittle-stars from the abyss are known to be brilliantly phosphorescent, and there are some vivid accounts of the light given off by Worms and various kinds of deep-sea Polyps found in the dredge.

It is possible that some of the more minute forms of life that occur on the mud at the bottom may also be phosphorescent. The Phæodaria, a family of Radiolarians peculiar to deep water, provided with thick heavy shells, have a curious organ in their bodies which may be capable of emitting light. If this is the case, it is not unreasonable to suppose that the vast tracts on the bed of the ocean may be faintly luminous like the surface of the sea on a calm night.

Among the other characters must be mentioned a very prevalent deficiency in the salts contained in the skeletons of these animals. The skin of the Fish is usually soft and velvety to the touch, the scales being either very thin and few in number or altogether missing; the bones are described as being so soft that it is easy to pass a needle through them. The shells of the Crustaceans, although frequently drawn out into numerous long and pointed spines, are usually deficient in carbonate of lime. The shells of the Molluscs are, when compared with those that live in shallower water, thin and brittle. The Corals do not seem in this respect to show much variation from their shallow water relations. Some of the solitary forms seem to have rather thinner shells, but the colonial genera have, as a rule, as good a support of carbonate of lime in the abyss as elsewhere.

Before proceeding to the next character, it is necessary to digress a little to consider the food of the animals in the abyss. In the absence of any direct sunlight there can be no vegetable growth, all of the animals must therefore be carnivorous. The food must be either the living bodies of the truly abysmal animals, or the dead bodies of those that fall from the surface waters.

It is probable that the bodies of Fish and the larger Invertebrates only rarely reach the bottom, as they have to run the gauntlet of many different forms of life living within 100 fathoms of the surface. When, therefore, such a prize does fall to the luck of a deep-sea Fish, it is important that it should have accommodation for it before the neighbours come to share the meal. This may be the cause of the fact that deep-sea Fish have, as a general rule, jaws and stomach that are extravagantly large, even for a carnivorous creature. The width of the gape and the extensibility of the stomach reach their highest grade in some of the deep-sea Eels, which have been found containing Fish actually larger than themselves. In these cases the stomach and the body wall hang down from the under side of the Eel’s body in the form of an enormous membranous sac containing the prey.

We have now considered very briefly some of the principal modifications of structure exhibited by the animals of the deep-sea, but before leaving the subject altogether it is necessary to refer to a few of the more characteristic and remarkable forms.

Although it may be considered to be one of the greatest scientific triumphs of the century to have discovered the existence of animal life in a region, which nearly all the distinguished men of science of the last generation believed to be as lifeless as the moon, the revelations of the dredge brought with them a certain amount of disappointment.

The study of the crust of the earth has revealed to us the fact that in times long since gone by, there existed not only the hairy Mammoths, the Iguanodons, and many other terrestrial monsters; but that the sea was peopled with certain Reptiles, Fish, Molluscs, Echinoderms and Crustaceans, which are now believed to be extinct.

When it was first discovered that some forms of animal life had attached themselves to a telegraph cable lying in 1200 fathoms, and that it was therefore a fact that life existed in very deep water, a successful application was made by scientific men to the British Government to assist them in a thorough survey of this hitherto unknown field of investigation.

The result of the voyages of H.M.S. Lightning and H.M.S. Porcupine was to prove the existence in water of 1000 fathoms in depth of a rich Fauna of rare and very remarkable animals. Among them were several new genera of Sea-lilies and a very curious Heart-urchin. The Sea-lilies that were then known to live in shallow water were very few in number, and nearly all of them were free and unattached. Now, in past times in the history of the earth different genera and species of stalked Crinoids or Sea-lilies were very plentiful, and from their abundance in certain geological deposits, it is believed that they lived in enormous numbers. The discovery of the new genera of stalked Crinoids in the abyss suggested that possibly there might be found several other families of extinct animals still surviving in the deep sea. This view was supported by the Heart-urchin, whose shell showed some striking peculiarities that were only known in fossil genera.

But the hopes that were felt, even if they were not always expressed, were doomed to disappointment. No living Ichthyosauruses or Plesiosauruses, none of the remarkable Ganoid fish of Devonian times, no Trilobites, no Cystoids nor Blastoids,--in fact none of the most interesting of the fossil types rewarded the investigators of the Challenger and subsequent expeditions.

It is perfectly clear to us now that, taken as a whole, the deep-sea Fauna is not more ancient in character than any other Fauna. It is true that a few genera, such as those just referred to, have survived, probably from very ancient times, without much modification; but the vast majority of forms are simply shallow water animals, which have been profoundly modified in structure, and adapted to the peculiar conditions of existence in the great depths of the ocean.