Another important subject, with the discussion of which Chamisso was associated, likewise relates to the pelagic fauna, but also belongs as much to geology and physical geography as to biology. It is that of the origin of the co-called sunken islands or atolls of the south seas and the Indian Ocean. It has been recognized from the first that these islands are the work of organic architects, the coral polyps, which absorb lime from the sea-water and build their oceanic castles with it.
After Johann Reinhold's theory that the ring-walls were built by the polyps from the depths of the ocean, and Henrik Steffens's hypothesis of submarine craters, came Darwin's celebrated theory, which supposed that the corals were built upon a substructure already existing in the ocean-bottom which gradually subsided under a continuous volcanic action so as to keep the rising structure at about the same level; and after that the contradiction of it by Murray and Wyville Thomson, on the basis of observations made during the Challenger Expedition, which pointed to a rise of the substructure. Here comes in a fundamental observation with which Chamisso's name has been associated, to the effect that the coral animals, never moving away from the one spot to which they attach themselves, need a stirring sea to bring them food, oxygen, and lime. Hence an atoll will rise wherever there is a suitable foundation, at not too great depth, on which the polyps can fix themselves; and as they thrive better on the edge of their ring, where they are favored by wave-beats and currents than in the middle, a ring-wall will rise, which should be higher, as is the case, on the windward side, where the wave-motion is strongest. These facts have been put prominently forward in all the discussions that have been had on the subject; and Chamisso has been credited with having been the first person who observed and mentioned them. I am obliged to disclaim Chamisso's title to this honor. The observation was first ascribed to Chamisso by Darwin, who says, in his Coral Reefs, "The larger kinds of corals, 'which form rocks measuring several fathoms in thickness,' prefer, according to Chamisso, the most violent surfs"; and from Darwin's it has passed into other works. A study of Chamisso's writings will show that, while he acccurately examined and described the atolls petrographically, geognostically, and zoölogically, he never made that remark. Darwin's mistake originated in his attributing to Chamisso a remark which appears at the end of the third volume of Kotzebue's First Voyage (containing also Chamisso's Remarks and Observations), in an Appendix from other Authors, which, there is abundant evidence to show, was made not by him but by Eschscholtz.
"The coral reefs and islands of the great ocean," says Chamisso in Ansichten von der Pflanzenkunde und dem Pflanzenreiche,
