1. Weber, Meckel' Arch. Anat. (1827) (cited by Herrick, C. J., Bull. U.S. Fish Comm., 22, 237 (1903)).
2. Schwalbe, G., Arch. Mikrosk. Anat., 3, 504 (1867).
3. Loven, C., Arch. Mikrosk. Anat., 4, 96 (1867).
4. Herrick, C. J., Bull. U.S. Fish Comm., 22, 237 (1903).
5. Parker, G. H., Smell, Taste and Allied Sense in the Vertebrates, 105 (J. B. Lippincott Co., Philadelphia and London, 1922).