Vertebrata.
(386) A. Boettcher. “Bau u. Entwicklung d. Schnecke.” Denkschriften d. kaiserl. Leop. Carol. Akad. d. Wissenschaft., Vol. XXXV.
(387) C. Hasse. Die vergleich. Morphologie u. Histologie d. häutigen Gehörorgane d. Wirbelthiere. Leipzig, 1873.
(388) V. Hensen. “Zur Morphologie d. Schnecke.” Zeit. f. wiss. Zool., Vol. XIII. 1863.
(389) E. Huschke. “Ueb. d. erste Bildungsgeschichte d. Auges u. Ohres beim bebrüteten Küchlein.” Isis von Oken, 1831, and Meckel’s Archiv, Vol. VI.
(390) Reissner. De Auris internæ formatione. Inaug. Diss. Dorpat, 1851.
Accessory parts of Vertebrate Ear.
(391) David Hunt. “A comparative sketch of the development of the ear and eye in the Pig.” Transactions of the International Otological Congress, 1876.
(392) W. Moldenhauer. “Zur Entwick. d. mittleren u. äusseren Ohres.” Morphol. Jahrbuch, Vol. III. 1877.
(393) V. Urbantschitsch. “Ueb. d. erste Anlage d. Mittelohres u. d. Trommelfelles.” Mittheil. a. d. embryol. Instit. Wien, Heft I. 1877.
Olfactory organ.
Amongst the Invertebrata numerous sense organs have been described under the title of olfactory organs. In aquatic animals they often have the form of ciliated pits or grooves, while in the Insects and Crustacea delicate hairs and other structures present on the antennæ are usually believed to be organs of smell. Our knowledge of all these organs is however so vague that it would not be profitable to deal with them more fully in this place. Amongst the Chordata there are usually well developed olfactory organs.
Amongst the Urochorda (Tunicata) it is still uncertain what organs (if any) deserve this appellation. The organ on the dorsal side of the opening of the respiratory pharynx may very possibly have an olfactory function, but it is certainly not homologous with the olfactory pits of the true Vertebrata, and as mentioned above (pp. 436 and 437), may perhaps be homologous with the pituitary body.
Fig. 307. Views of the head of Elasmobranch embryos at two stages as transparent objects.
A. Pristiurus embryo of the same stage as fig. 28 F.
B. Somewhat older Scyllium embryo.
III. third nerve; V. fifth nerve; VII. seventh nerve; au.n. auditory nerve; gl. glossopharyngeal nerve; Vg. vagus nerve; fb. fore-brain; pn. pineal gland; mb. mid-brain; hb. hind-brain; iv.v. fourth ventricle; cb. cerebellum; ol. olfactory pit; op. eye; au.V. auditory vesicle; m. mesoblast at base of brain; ch. notochord; ht. heart; Vc. visceral clefts; eg. external gills; pp. sections of body cavity in the head.