Abstract
PROGRESS in the classification of corals has been a passage from fog to fog across lucid intervals cleared by successive systems, which have collapsed under the efforts to improve them. The primæval darkness of Ellis, Guettard and Esper was first lightened in 1830 by the classification of de Blainville, which was obsolete within four years of its publication. A long series of memoirs by Edwards and Haime, begun in 1848, gradually laid the foundations of a system at once more adequate to the wide variations in coral structure, and more natural; but it was not until 1857–60 that the two authors' complete classification was published in the great “Histoire Naturelle des Coralliaires.” The essential features of their scheme were the separation of the Palæozoic corals as the order Rugosa, and the division of the later corals into two orders, the Aporosa and Perforata, characterised respectively by a solid and a porous wall. The classification gave helpful guidance to those who chose to use it; but many authors preferred to follow de Fromentel, who in 1861 issued a more artificial but simpler system, based on the mode of association of individual corallites into compound coralla. The life of Fromentel's classification was, from its nature, necessarily brief; while that of Edwards and Haime was weak in so many points, that under the numerous amendments of Etallon, Milaschewitsch, yon Zittel, and others, the original boundaries became indefinite, and the system once more involved in fog. In 1884, P. M. Duncan restored order by a revision of the genera of Neozoic corals; he adopted, in the main, the same principles as Edwards and Haime, and his revision is still the most useful handbook to coral classification. It has held this position in spite of repeated attempts to change the whole basis of classification. Thus Pratz in 1882 proposed a scheme founded on the septa; von Heider and Ortmann have advocated another, resting on the formation of the “wall”; and recently Miss Ogilvie has suggested a new arrangement, even more radical in its changes.
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