. Journal of morphology . ilibration and thedetection of vibrations of low frequency when such come to the ani-mal through a dense medium such as earth or water. The natureand structure of the apparatus in urodeles seem to preclude the beliefthat vibrations of any frequency whatsoever can be detected froma medium as rare as the air. There is, however, nothing in thenature of the apparatus to interfere with the view that vibrations The Columella Auris in Ampiiibia. 610 of high frequency are not detected if transmitted to the animalthrough a dense medium. Experimentation along this line mayprove
. Journal of morphology . ilibration and thedetection of vibrations of low frequency when such come to the ani-mal through a dense medium such as earth or water. The natureand structure of the apparatus in urodeles seem to preclude the beliefthat vibrations of any frequency whatsoever can be detected froma medium as rare as the air. There is, however, nothing in thenature of the apparatus to interfere with the view that vibrations The Columella Auris in Ampiiibia. 610 of high frequency are not detected if transmitted to the animalthrough a dense medium. Experimentation along this line mayprove very interesting and valuable. During the larval period, and in aquatic or partly aquatic formsduring adult life, the connection of the fenestral plate is with thesuspensorium. Thus it would appear that jars or vibrations aretransmitted from the objects, upon which they are resting, to thefloor of the mouth, after which the course is through the suspen-sorium to the columella and thence to the inner ear, as has been StC,. M. L H. a. Fig. 21a. Schema to illustrate the possible method of communication be-tween the inner ear and the exterior for larvae and thoroughly aquatic adultforms. Col., Columella; , fenestra vestibuli; , hyoid arch; , liga-mentum squamoso-columellare; , skeleton of the lower jaw; Pg., paloto-quadratum; 8p., os squamosum; , stilus columellse. suggested by Gaupp (05, 07). The possibility of such a functionalmechanism is illustrated in Fig. 21a. At transformation when terrestrial life is assumed, in certainforms, a different type of communication with the exterior is columella becomes fused with the ear capsule while a free plate,the operculum, is formed behind and below as in Ambystoma orthe caudal portion of the fenestral plate remains free as in thePlethodontidse and some others. This plate is placed in communi-cation with the exterior by the M. opercularis, connecting it withthe shoulder girdle. Thus jars and vibrations may
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