517 Naumann, C. F., Ueber die Spiralen von Conchylien, Abh. k. sûÊchs. Ges. pp. 153ã196, 1846; Ueber die cyclocentrische Conchospirale u. û¥ber das Windungsgesetz von Planorbis corneus, ibid. I, pp. 171ã195, 1849; Spirale von Nautilus u. Ammonites galeatus, Ber. k. sûÊchs. Ges. II, p. 26, 1848; Spirale von Amm. Ramsaueri, ibid. XVI, p. 21, 1864; see also Poggendorffãs Annalen, L, p. 223, 1840; LI, p. 245, 1841; LIV, p. 541, 1845, etc.
518 Sandberger, G., Spiralen des Ammonites Amaltheus, A. Gaytani, und Goniatites intumescens, Zeitschr. d. d. Geol. Gesellsch. X, pp. 446ã449, 1858.
519 Grabau, A. H., Ueber die Naumannsche Conchospirale, etc. Inauguraldiss. Leipzig, 1872; Die Spiralen von Conchylien, etc. Programm, Nr. 502, Leipzig, 1882.
521 A beautiful construction: stupendum Naturae artificium, Linnaeus.
522 English edition, p. 537, 1900. The chapter is revised by Prof. Alpheus Hyatt, to whom the nomenclature is largely due. For a more copious terminology, see Hyatt, Phylogeny of an Acquired Characteristic, p. 422 seq., 1894.
523 This latter conclusion is adopted by Willey, Zoological Results, p. 747, 1902.
524 See Moseley, op. cit. pp. 361 seq.
525 In Nautilus, the ãhoodã has somewhat different dimensions in the two sexes, and these differences are impressed upon the shell, that is to say upon its ãgenerating curve.ã The latter constitutes a somewhat broader ellipse in the male than in the female. But this difference is not to be detected in the young; in other words, the form of the generating curve perceptibly alters with advancing age. Somewhat similar differences in the shells of Ammonites were long ago suspected, by DãOrbigny, to be due to sexual differences. (Cf. Willey, Natural Science, VI, p. 411, 1895; Zoological Results, p. 742, 1902.)