[12] J. Graham Kerr, The Budgett Memorial Volume.
[13] J. Phelps, Science, vol. N.S. ix. p. 366; J. Eycleshymer and Wilson, Amer. Journ. Anat., v. 1906, p. 154.
[14]: F. Maurer, Morphol. Jahrb. ix., 1884, S. 229, and xiv., 1888, S. 175.
[15] J. Rückert, Arch. Entwickelungsmech. Band iv., 1897, S. 298; J. Graham Kerr, Phil. Trans. B. 192, 1900, p. 325, and The Budgett Memorial Volume.
[16] Cuvier et Valenciennes, Hist. nat. des poiss. xix., 1846, p. 151.
[17] J. Rathke, Üb. d. Darmkanal u.s.w. d. Fische, Halle, 1824, S. 62.
[18] Cf. W. Biedermann, Electro-Physiology.
[19] Literature in N. K. Koltzoff, Bull. Soc. Nat. Moscou, 1901, P. 259.
[20] J. Graham Kerr, Proc. Zool. Soc. Lond. (1901), p. 484.
[21] J. S. Budgett, Trans. Zool. Soc. Lond. xv. (1901), vol. p. 324.