The science of life : fully illustrated in tone and line and including many diagrams

BOOK 2

IS

CHAPTER 7

OUR KNOWLEDGE OF

THE FORMS OF LIFE COMPLETE?

§ 1 Sea-serpents and Living Dinosaurs

EFORE we leave this survey of the forms

and phyla of life, we may perhaps give a little space to the question how far this survey may be considered comprehensive. Does much remain unknown? In the fossil record certainly we may almost count upon remarkable types in store, but here we are concerned with things still living. That there is still much to be revealed by ultra-microscopic methods is manifest from the concluding section of the previous chapter. Apart from that, is it possible that a number of large, exciting creatures still live undiscovered in remote and shadowy and inaccessible corners? The exploration of the land surface of our globe is proceeding more and more rapidly, but there are still places, barren heights and luxuriant, pestilential jungles where the describing and classifying white man has hardly penetrated. And in the sea there are vast regions that have been barely sampled by the drift-net, the trawl, and the dredge.

It is from the sea particularly that rumours of strange beasts come, glimpsed momentarily by sailors, and then plunging down into the unsearchable deep. The favourite marvel of the nineteenth century was the “ seaserpent” of enormous proportions. This reappeared annually and was annually discussed and disposed of. Now it was a school of dolphins swimming end to end and now a sulphur-bottom whale seen by unaccustomed observers ; now a great basking shark, now an actual sea-snake (for such there are as big as ten feet long) with its proportions all exaggerated, and now a brilliant effort of the unaided, creative imagination. Did such an undescribed monster exist it is incredible that no bone, no scrap cast up upon a beach, no floating corpse of it has ever been recorded. A single tooth, a single vertebra, said Professor Owen long ago, would suffice to establish its identity scientifically. A certain number of species of giant squid and octopus may still be eluding the naturalist in the middle deeps in which these cephalopods abound. Several species and one genus are known only from fragments ejected by sperm whales in their death flurries. But there is nothing very

sensational for the general reader in the discovery merely of new genera.

There is, however, another possibility of strange things in the sea. The discovery of living creatures in the extreme depths of the ocean is very recent. It was held as recently as 1840 that there was no life, animal and vegetable, deeper than three hundred fathoms. But since then there have been a number of successful experiments in deep-sea collecting. The three-and-a-half years’ expedition of the British ship Challenger (1872-76) is the classic piece of ocean exploration ; it laid the foundations of the science of oceanography which many other expeditions have since expanded and elaborated. In the first excitement of the discovery of living things even in the deepest abyss it was thought that we should find new phyla altogether, new plans of animal organization, and that in these deep secluded places some of the ancestral forms of life might have been preserved from great antiquity. The intensive researches that have since taken place have made such hopes untenable. The creatures that come up from abysmal depths are weird indeed, but they are not fundamentally different from those that live in more accessible places. They are grotesque distortions of the fishes, crabs, seacucumbers, and so on that we already know. They are not in any sense primitive ;_ they are, on the contrary, highly specialized. Indeed, it is becoming more and more evident that the abyss is a region as different from the original home of living things as dry land. There is no light in the abyss and therefore there are no plants; the creatures that inhabit it live on each other or on the corpses that float down from higher layers, from which it follows that they cannot have been the first forms of life. “They are a comparatively recent evolution, members of the phyla that were already established above, adapting themselves to that new and at first quite inhospitable environment.

On land, it is equally improbable that we shall discover anything strikingly new. There are jungles that have hitherto proved too lush and too pestilential to be systematically explored, and here it may be that unknown creatures lurk. There was a time when tropical forests and jungle occupied much more of the surface of the world than they do now, and were inhabited, as the

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