Coralline

“ And now if I hand round two specimens—one a coralline, and the other something you do not yet know—I am sure you will say at first sight that they belong to the same family, and, in fact, if you buy at the seaside a group of seaweeds gummed on paper, you will most likely get both these among [Pg 179] them. Yet the truth is, that while the coralline (1, Fig. 66) is a plant, the other specimen (2) which is called Sertularia filicula, is an animal.
Fig. 66. Coralline and Sertularia, to show likeness between the animal Sertularia and the plant Coralline. ”

“ The most transparent ones he will find the best to discover their gelatinous inside, which runs thro' the stem and ramifications, and ends in the heads, where the claws are. Some of the best kinds to observe are as follows: The sea-oak coralline, the lily-flowering coralline, the great tooth coralline, the sea-thread coralline, and the branched tubular coralline. ”

“ Every fact in geology proclaims that neither the land, nor the bed of the sea retain for indefinite periods the same level. As well might it be imagined that the British Seas would in time become choked up with beds of oysters, or that the numerous small corallines off the inhospitable shores of Tierra del Fuego would in time form a solid and extensive coral-reef. ”

“ The coral-like Nullipora is the last and bounding plant of this zone in our seas, and rarely ranges with us below 20 fathoms at the utmost; though in more southern seas, as in the Mediterranean, it is found abundantly at depths as great as 70 and 80 fathoms, where, as here, it forms the out-post of marine vegetation in depth. [14] The third province in depth I have termed the Region of Corallines, for in it we find the greatest variety and abundance of the corneous zoophytes—arborescent animals, which seem here to take the place of plants. ”

“ In warm seas the most conspicuous of rock-making organisms are the corals known as the reef builders. Floating in a boat over a coral reef, as, for example, off the south coast of Florida or among the Bahamas, one looks down through clear water on thickets of branching coral shrubs perhaps as much as eight feet high, and hemispherical masses three or four feet thick, all abloom with countless minute flowerlike coral polyps, gorgeous in their colors of yellow, orange, green, and red. ”

“ On the weather-side, exposed to the long sweep of the ocean-rollers, there are but short, black-looking reefs backed by irregular piles of loose, flat, sea-worn coral, thrown up and accumulating till its surface is brushed by the pendant leaves of the cocoanuts, only to be washed and swirled back seawards when the wind comes from the westward and sends a fierce sweeping current along the white beaches and black coral rocks alike. ”

“ We found a field of coral about half a mile square, dry at low water, with the surf breaking very high on the outer edge, which lies exposed to the waves from the north. The surface of the rock is every where worn into small holes, which being left full of water as the tide goes out, are occupied by a number of beautiful blue fish. The coral is exceedingly hard, and though at many places it sticks up in sharp points, it requires a hammer of considerable weight to break it, and emits sparks like flint when struck; in a short time it entirely defaces the hammer. ”

“ The most wonderful of all coral is that found in the coral reefs, which are so old that the most ancient fish in all fishdom, or his great-grandfather before him, could not tell when they were begun; and so hard and enduring that the storms of centuries have never been able to destroy them. But strong as they are, the mighty ocean, (both friend and foe to the coral) , is still stronger, and in time the constant washing and beating of the tides wear away portions of the hard rock, changes the formation of the reefs, and helps in a large measure in the making of the lovely coral islands. ”

“ Then there are coral islands in the Pacific Ocean, whole platforms of solid coral which shut in portions of quiet water in some places.
The little corals themselves do not work in deep water, nor above the surface of the sea. But the bony substance spreads and spreads, up, down, and across the sea. And as many shell-fish eat into coral, great quantities of fine coral-sand sink to the bottom, making a nice white carpet for the fishes to glide over. Folks do not take coral from the sea at any time but during the months you call April, May, and June. ”

“ You are right, Fritz; coral consists of the calcareous cells of minute animals, so built up as to form a tree-like structure.
“The coral fishery gives employment to many men in the Persian Gulf, the Mediterranean Sea, and other places. The instrument commonly used, consists of two heavy beams of wood, secured together at right angles, and loaded with stones. Hemp and netting are attached to the under side of the beams, to the middle of which is fastened one end of a strong rope, by which the apparatus is let down from a boat, and guided to the spots where the coral is most abundant. ”

“ A mast is sunk at the side of the boat, and the diver descends this; gathering the sponges found near the bottom of the pole.
Next in order of fishing in deep sea, comes coral fishing. The ancients believed that the coral was a plant, but it is now known that the coral is constructed by a family of polyps living together, and constituting a polypidom. It abounds in the waters of the Mediterranean where upon rocky beds like a submarine forest, the red coral, the most brilliant and celebrated of all coral, grows at various depths, rarely less than five fathoms, or more than one hundred. ”

“ Eastern coast.—I have felt the greatest doubt about colouring any portion of this coast, north of the fringing-reefs round the Farsan Islands in 16° 10′. There are many small outlying coral-reefs along the whole line of coast; but as the greater number rise from banks not very deeply submerged (the formation of which has been shown to be only secondarily connected with the growth of coral) , their origin may be due simply to the growth of knolls of corals, from an irregular foundation situated within a limited depth. ”

“ Coral growth will be most luxuriant in the shallow water, and the first stage of our reef will be a mound of coral of the shape shewn in section by the dotted area. Between E and D this comes to the surface, and the corals, projecting above the water at lowest spring tides, are killed at the top, so that E to D becomes an almost flat surface of dead corals, some of which may, however, be still living where their bases are immersed in clear sea-water. ”

“ Further, it is easy to see that these differ from the fossils of home limestones in their extreme abundance, in their lying loose among the surrounding sand, and in their being familiar to the collector of shells as common species still living in the neighbouring sea. The same is true of the corals, though in this case the identification is not quite so obvious. The fact is we are walking upon a coral-reef, almost exactly like those still forming and growing in the sea, which has been elevated by earth movements above the water, and every grain of the earth was once part of a living creature. ”

“ To the coral-fishers of the Mediterranean, who seek the precious red coral, which grows firmly fixed to rocks at a depth of sixty to eighty fathoms, both the dredge and the trawl would be useless. They, therefore, have recourse to a sort of frame, to which are fastened long bundles of loosely-netted hempen cord, and which is lowered by a rope to the depth at which the hempen cords can sweep over the surface of the rocks and break off the coral, which is brought up entangled in the cords. A similar contrivance has arisen out of the necessities of deep-sea exploration. ”

“ The coral animals must build on some foundation. They must begin by attaching themselves to something solid. Every coral reef, therefore, whatever be its form—every line of barrier-reef however long—every ring however small or however wide, must indicate some corresponding arrangement of subjacent rock. What cause can have arranged the rocky foundations of the coral in such curious shapes? Extreme cases of any peculiar phenomenon are always those which most attract attention, and sometimes they are the cases which most readily suggest an explanation. ”

“ No other formation affords such decisive evidence of the effective part which the coral animals have taken in the formation of the upper strata of the globe. The members of this group, in their protracted parallel layers and defined terraces, exhibit, in unaltered position, walls of rock built up entirely of coral, and, at the foot of these, huge masses of coral debris which have been cemented by finely comminuted particles of lime, telling of the raging surf that broke against those reefs in days of old. ”

“ The modern corals present to us a great diversity of structure, but they are excelled in all respects by those of the old world. The remains of these labours of insect life are exceedingly numerous; entire mountains are built, for the most part, with them; and the coral animals appear to have been as busy in the ocean which washed the cliffs of the Silurian boundary as it is at the present time on the reefs of Torres Straits and over the Indian Seas. Fig. ”

“ It seems to me, that when the animalcules which form the corals at the bottom of the ocean, cease to live, their structures adhere to each other, by virtue either of the glutinous remains within, or of some property in salt water; and the interstices being gradually filled up with sand and broken pieces of coral washed by the sea, which also adhere, a mass of rock is at length formed. Future races of these animalcules erect their habitations upon the rising bank, and die in their turn to increase, but principally to elevate, this monument of their wonderful labours. ”

“ I do not, however, suppose that if a vast number of soundings were obtained round these islands, the limit above assigned would be found never to vary, but I conceive the facts are sufficient to show, that the exceptions would be few. The circumstance of a gradual change, in the two cases, from a field of clean coral to a smooth sandy bottom, is far more important in indicating the depth at which the larger kinds of coral flourish than almost any number of separate observations on the depth, at which certain species have been dredged up. ”

“ We found ourselves within a cable's length of a shoal and all round shoals of sand and extensive coral reefs. Latitude observed 20 degrees 51 minutes 38 seconds south.
"Sunday, October 10th. P.M. Sent the boat to examine the reefs of coral near us. At 4 P.M. the boat returned on board; found the coral to be of many different colours—blue, yellow, green, and in short in every colour we know of—found some very large cockles and a few small shells—found the tide to ebb to run due north-east not less than 2 1/2 knots but when it sallys over the flats and reefs it may be 5 knots. ”

“ Darwin's views, the presence of a lagoon coral island is an evidence of depression of the solid land there; and, on the contrary, marginal coral reefs often supply evidence of rising, in addition to that furnished by shelly beaches at high levels. Thus may we comprehend, in the former case, the formation of a long bank of coral, by the successive submersion of a line of mountain summits ”

“ Many of the large hemispherical corals live on the reef like loose stones, but on turning them over one may find quite a small shell, or coral branch, attached to the centre of the underside. This is the foundation of the whole, the resting place of the tiny floating larva, the growth of which first covered the stone on which it settled by a vigorous colony which when large enough to be independent of support continued its growth until the mass exceeded by hundreds of times the bulk of the original foundation. ”

“ Between the outer margin and the beach, there is a flat space with a sandy bottom and a few tufts of living coral; in some parts it is so shallow, that people, by avoiding the deeper holes and gullies, can wade across it at low water; in other parts it is deeper, seldom however exceeding ten or twelve feet, so that it offers a safe coasting channel for boats. ”

“ As the lagoons of atolls are sometimes even more than forty fathoms deep, it must, also, be assumed on this view, that at a depth at which the waves do not break, the coral grows more vigorously on the edges of a bank than on its central part ”

“ When the coral reef has thus reached the surface and cannot grow farther in height, it spreads radially like a fairy ring on the talus formed by broken corals that have fallen down the slopes. The central parts, no longer protected by living organisms, are continually subject to the solvent action of the sea water penetrating the porous substratum, and sink to form the lagoon. ”

“ When we discuss the origin of the different classes of coral formations, we shall see that the submerged state of the whole of some atoll-formed reefs, and of portions of others, generally but not invariably on the leeward side, and the existence of more deeply submerged banks now possessing little or no signs of their original atoll-like structure, are probably the effects of a uniform cause,—namely, the death of the coral, during the subsidence of the area, in which the atolls or banks are situated. ”

“ The specimens of corals which one sees in collections, or made into ornaments, are the calcareous skeletons of various kinds of the coral polyps. Some of the corals live together in enormous numbers, forming branching colonies fixed as closely together as possible, and secrete while living a stony skeleton of carbonate of lime. These skeletons persist after the death of the animals, and because of their abundance and close massing form great reefs or banks and islands. These coral reefs and islands occur only in the warmer oceans. ”