Gilbert Charles Bourne

“ In face of this accumulated evidence, it must be admitted that the subsidence theory of Darwin is inapplicable to a large number of coral reefs and islands, but it is hardly possible to assert, as Murray does, that no atolls or barrier reefs have ever been developed after the manner indicated by Darwin. The most recent research on the structure of coral reefs has also been the most thorough and most convincing. It is obvious that, if Murray’s theory were correct, a bore hole sunk deep into an atoll would pass through some 100 ft. ”

“ Where the barrier reef is not far from the land there are always gaps in it opposite the mouths of rivers or considerable streams. The outer wall of a barrier reef is steep, and frequently, though not always, descends abruptly into great depths. In many cases in the Pacific Ocean a barrier reef surrounds one or more island peaks, and the strips of land on the edge of the reef may encircle the peaks with a nearly complete ring. An atoll is a ring-shaped reef, either awash at low tide or surmounted by several islets, or more rarely by a complete strip of dry land surrounding a central lagoon. ”

“ He pointed out that the larger and more massive species of corals flourish best on the outer sides of a reef, whilst the more interior corals are killed or stunted in growth by the accumulation of coral and other debris. Thus the outer edge of a submerged reef is the first to reach the surface, and a ring of land being formed by materials piled up by the waves, an atoll with a central lagoon is produced. ”

“ In addition to these and other exacting lines of research and the ordinary duties of his chair, Weldon took a leading part in the work of the association for promoting a professorial university for London, and his friends, fearing that he was over-straining his energies, hailed with relief his election to the Linacre professorship of comparative anatomy at Oxford in February 1899. But though Oxford afforded opportunities for greater intellectual leisure, Weldon disdained to make use of them. ”

“ Thus the reef will rise to the surface as an atoll, and the nearer it approaches the surface the more will the corals on the exterior faces be favoured, and the more will those in the centre of the reef decrease, for experiment has shown that the minute pelagic organisms on which corals feed are far less abundant in a lagoon than in the sea outside. ”

“ The outer wall of an atoll generally descends with a very steep but irregular slope to a depth of 500 fathoms or more, but the lagoon is seldom more than 20 fathoms deep, and may be much less. Frequently, especially to the leeward side of an atoll, there may be one or more navigable passages leading from the lagoon to the open sea.
Though corals flourish everywhere under suitable conditions in tropical seas, coral reefs and atolls are by no means universal in the torrid zone. ”

“ His leisure hours at Oxford were spent in long bicycle rides, during which he studied the fauna of the neighbourhood; his vacations were spent in journeys to various parts of the continent, where he worked at his statistical calculations and collected material for fresh lines of research. He added to his labours by undertaking the co-editorship of ‘Biometrika,’ a new scientific journal devoted to his special branch of study, and contributed to it twelve separate original and critical papers between 1901 and 1906. ”

“ For although they may at first be too far below the surface for reef-building corals, they afford a habitat for numerous echinoderms, molluscs, crustacea and deep-sea corals, whose skeletons accumulate on their summits, and they further receive a constant rain of the calcareous and silicious skeletons of minute organisms which teem in the waters above. ”

“ At Plymouth he began the series of original researches which established his reputation. Until 1888 he was engaged on the morphological and embryological studies which seemed to contemporary zoologists to afford the best hope of elucidating the problems of animal evolution. ”

“ In the Pacific Ocean there is a vast area thickly dotted with coral formations, extending from 5° N. lat. to 25° S. lat., and from 130° E. long, to 145° W. long. There are also extensive reefs in the westernmost islands of the Hawaiian group in about 25° N. lat. In the Indian Ocean, the Laccadive and Maldive islands are large groups of atolls off the west and south-west of India. Still farther south is the Chagos group of atolls, and there are numerous reefs off the north coast of Madagascar, at Mauritius, Bourbon and the Seychelles. ”

“ By these agencies the banks are gradually raised to the lowest depth at which reef-building corals can flourish, and once these establish themselves they will grow more rapidly on the periphery of the bank, because they are more favourably situated as regards food-supply. ”

“ But the larger number of species, particularly the more massive kinds, occur only in tropical seas in shallow waters, whose mean temperature does not fall below 68° Fahr., and they do not flourish unless the temperature is considerably higher. ”