. Outlines of the comparative physiology and morphology of animals. Anatomy, Comparative; Physiology, Comparative. SENSE ORGANS. 185 verberatory cavity, with a tense membrane, ty (which may be compared to a membrana tympani, or, better, with the membrane of the foramen ovale), a vestibular sac, auv, containing otoliths (Fig. 117). In crustaceans is found a similar organ, sometimes on the anterior lower surface of the cephalothorax, as in crabs, and sometimes on the basal joint of the antennae, as in lobsters. Mollusca.—In cephalopod mollusks the hearing organ is in the head just below the brai
. Outlines of the comparative physiology and morphology of animals. Anatomy, Comparative; Physiology, Comparative. SENSE ORGANS. 185 verberatory cavity, with a tense membrane, ty (which may be compared to a membrana tympani, or, better, with the membrane of the foramen ovale), a vestibular sac, auv, containing otoliths (Fig. 117). In crustaceans is found a similar organ, sometimes on the anterior lower surface of the cephalothorax, as in crabs, and sometimes on the basal joint of the antennae, as in lobsters. Mollusca.—In cephalopod mollusks the hearing organ is in the head just below the brain, as a cavity in the cartilage filled with endolymph and containing otoliths (Fig. 118). In gastropods it is a capsule of con- cf densed connective tissue lined with epithelium, filled with liquid and con- taining otoliths, situated just below the oesophag- eal ganglion.* In aceph- ala a similar capsule has been found at the base of the gills which is sup- posed to have a similar function. Below this a hearing organ has not been found. Whether there be a nerve specialized for hearing is not known, as we can judge only by the existence of some apparatus like a capsule and otoliths. Thus far the most essential part of the ear is the vestibular sac with its otoliths. But in spiders and certain insects there is found another type of hear- ing organs which may be compared not to the vestibular sac, but to the hairs of the ampullae. In spiders, on the feelers are found cup-shaped hollows, from the bottom. Fig. 118.—Section through the head of a squid, showing the auditory organ : vst vestibular sac and otoliths; eg, cephalic ganglion ; e, the eye. * Nat., iv, 518 ; Arch, des Sci., xliv, 261, 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 LeConte, Joseph, 1823-1901. New York, D. Appleton and Company
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