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Polyps and echinoderms abounded on the seafloor: various isis coral, cornularian coral living in isolation, tufts of virginal genus Oculina formerly known by the name "white coral," prickly fungus coral in the shape of mushrooms, sea anemone holding on by their muscular disks, providing a literal flowerbed adorned by jellyfish from the genus Porpita wearing collars of azure tentacles, and starfish that spangled the sand, including veinlike feather stars from the genus Asterophyton that were like fine lace embroidered by the hands of water nymphs, their festoons swaying to the faint undulations caused by our walking.
At the latter, the first cast of the large dredge was made on a ledge of shoals in a depth of eighty fathoms, and, among countless other things, a number of stemmed crinoids and comatulae were brought up. An ardent student of the early fossil echinoderms, it was a great pleasure to Agassiz to gather their fresh and living representatives.
Bivalve and univalve mollusca seem to be rare at the greatest depths; but starfishes, sea urchins and other echinoderms, zoophytes, sponges, and protozoa abound. It is obvious that the Challenger has the privilege of opening a new chapter in the history of the living world. She cannot send down her dredges and her trawls into these virgin depths of the great ocean without bringing up a discovery.
The objection that broad statements of this kind, after all, rest largely on negative evidence is obvious, but it has less force than may at first be supposed; for, as might be expected from the circumstances of the case, we possess more abundant positive evidence regarding Fishes and marine Mollusks than respecting any other forms of animal life; and yet these offer us, through the whole range of geological time, no species ordinally distinct from those now living; while the far less numerous class of Echinoderms presents three; and the Crustacea two, such orders, though none of these come down later than the Paleozoic age.
The objection that broad statements of this kind, after all, rest largely on negative evidence is obvious, but it has less force than may at first be supposed; for, as might be expected from the circumstances of the case, we possess more abundant positive evidence regarding Fishes and marine Mollusks than respecting any other forms of animal life; and yet these offer us, through the whole range of geological time, no species ordinarily distinct from those now living; while the far less numerous class of Echinoderms presents three, and the Crustacea two, such orders, though none of these come down later than the Palæozoic age.
The hardly less startling hypothesis that the Echinoderms are coalesced worms, on the other hand, appears to be open to serious objection. As a matter of anatomy, it does not seem to me to correspond with fact; for there is no worm with a calcareous skeleton, nor any which has a band-like ventral nerve, superficial to which lies an ambulacral vessel.
The genera Poteriocrinus, Cyathocrinus, Pentremites, Actinocrinus, and Platycrinus, are all of them characteristic of this formation. Other Echinoderms are rare, a few Sea-Urchins only being known: these have a complex structure, with many more plates on their surface than are seen in the modern genera of the same group.
Of these we have no interest just now in the echinoderms, molluscs, and articulates, as they are independent branches of the animal-tree, and have nothing to do with the vertebrates. On the other hand, we are greatly concerned with a very interesting group that has only recently been carefully studied, and that has a most important relation to the ancestral tree of the vertebrates.
At many places corals formed thin reefs, as at Louisville, Kentucky, where the hardness of the reef rock is one of the causes of the Falls of the Ohio. Sponges, echinoderms, brachiopods, and mollusks were abundant. The cephalopods take a new departure.
Our dragnets brought up many specimens of polyps and echinoderms plus some unusual shells from the branch Mollusca. Captain Nemo's treasures were enhanced by some valuable exhibits from the delphinula snail species, to which I joined some pointed star coral, a sort of parasitic polypary that often attaches itself to seashells.
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