425 See for instance other excellent illustrations in Carpenterãs article ãShell,ã in Toddãs CyclopûÎdia, vol. IV. pp. 550ã571, 1847ã49. According to Carpenter, the shells of the mollusca (and also of the crustacea) are ãessentially composed of cells, consolidated by a deposit of carbonate of lime in their interior.ã That is to say, Carpenter supposed that the spherulites, or calôÙcoôÙspheôÙrites of Harting, were, to begin with, just so many living protoplasmic cells. Soon afterwards however, Huxley pointed out that the mode of formation, while at first sight ãirresistibly suggesting a cellular structure,ã...ãis in reality nothing of the kind,ã but ãis simply the result of the concretionary manner in which the calcareous matter is depositedã; ibid. art. ãTegumentary Organs,ã vol. V, p. 487, 1859. Quekett (Lectures on Histology, vol. II, p. 393, 1854, and Q. J. M. S. XI, pp. 95ã104, 1863) supported Carpenter; but Williamson (Histological Features in the Shells of the Crustacea, Q. J. M. S. VIII, pp. 35ã47, 1860) amply confirmed Huxleyãs view, which in the end Carpenter himself adopted (The Microscope, 1862, p. 604). A like controversy arose later in regard to corals. Mrs Gordon (M. M.
Ogilvie) asserted that the coral was built up ãof successive layers of calcified cells, which hang together at first by their cell-walls, and ultimately, as crystalline changes continue, form the individual laminae of the skeletal structuresã (Phil. Trans. CLXXXVII, p. 102, 1896): whereas v. Koch had figured the coral as formed out of a mass of ãKalkconcrementeã or ãcrystalline spheroids,ã laid down outside the ectoderm, and precisely similar both in their early rounded and later polygonal stages (though von Koch was not aware of the fact) to the calôÙcoôÙspheôÙrites of Harting (Entw. d. Kalkskelettes von Asteroides, Mitth. Zool. St. Neapel, III, pp. 284ã290, pl. XX, 1882). Lastly Duerden shewed that external to, and apparently secreted by the ectoderm lies a homogeneous organic matrix or membrane, ãin which the minute calcareous crystals forming the skeleton are laid downã (The Coral Siderastraea radians, etc., Carnegie Inst. Washington, 1904, p. 34). Cf. also M. M. Ogilvie-Gordon, Q. J. M. S. XLIX, p. 203, 1905, etc.