. Outlines of zoology. Zoology. ALIMENTARY AND RESPIRATORY SYSTEMS. 467 union of dorsal and ventral roots is only partial, and there is no sympathetic system. The eye is degenerate {, without a lens or iris), and is hidden beneath the skin ; the ear has only one semicircular canal; the single nasal sac opens dorsally at the apex of the head, and communicates posteriorly with the pharynx by a naso-palatine duct. The absence of pigment and sensory structures in the skin, and the degeneracy of the eye may be associated with the hag's mode of life. Alimentary System. The mouth is suctorial. Th
. Outlines of zoology. Zoology. ALIMENTARY AND RESPIRATORY SYSTEMS. 467 union of dorsal and ventral roots is only partial, and there is no sympathetic system. The eye is degenerate {, without a lens or iris), and is hidden beneath the skin ; the ear has only one semicircular canal; the single nasal sac opens dorsally at the apex of the head, and communicates posteriorly with the pharynx by a naso-palatine duct. The absence of pigment and sensory structures in the skin, and the degeneracy of the eye may be associated with the hag's mode of life. Alimentary System. The mouth is suctorial. There is a median tooth above, and two rows of teeth are borne on each side of the muscular "; These teeth are "horny," but sharp. Into the mouth, just in front of a fringed velum which. Fig. 150.—Median longitudinal section of anterior end of INIyxine. (After Retzius.) Showing barbules, nasal passage, mouth cavity, brain. separates it from the pharynx, the nasal sac opens. Thus water passes from the nostril into the pharynx. It may be, as Beard suggests, that this passage is a persistent "old ; From the gullet open six respiratory pouches, each of which has an efferent tube, but the six efferent tubes of each side unite and have a common exhalent orifice. The gut is straight and uniform, with longitudinal ridges internally, with a two-lobed liver and a gall bladder, but without the usual pancreas. Respiratory System. Water enters by the nasal sac, passes into the pharynx, down the gullet, into the six pairs of respiratory pouches,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933; Newbigin, Marion I. (Marion Isabel), 1869-1934; Smith, Preserved, 1880-1941. fmo. New York, D. Appleton & Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
