The caecilian ear.

A study of the ear and its responses to acoustic stimuli was carried out in two caecilian species, Geotrypetes seraphini and Dermophis mexicanus. There is no external ear opening or tympanic membrane. The middle ear mechanism consists of a single element, the stapes, with its footplate in the oval window and a headpiece extending anterolaterally to the quadrate. The inner ear contains a single auditory endorgan, the amphibian papilla, somewhat similar to this organ in anurans. The mode of stimulation by sounds, however, involves a reentrant fluid circuit as in certain of the reptiles. In terms of the electrical potentials this ear is rather uniformly sensitive, though in low degree, to tones over the low-frequency range.