The development of the ear of Acanthias vulgaris

A study of the development of the ear of the common dogfish from the 3.5‐mm. stage to the adult, with a brief review of the literature and comparison with related forms. The study includes the following topics: First indications of vesicles. The beginning of specialization. The separation of component structures. The sensory epithelium. The structure of the adult ear, including a description of the sensory areas, the innervation, the lagena. The position of the future canals is first indicated in 15‐ to 20‐mm. stages. The sacculus and utriculus were first noted in the 22‐mm. stage. Complete separation of the canals, the sacculus, utriculus, the recessus utriculus, and the lagena has occurred by the time the 33‐mm. stage is reached. Definite innervation of the ampullae is found at this stage. The article contains twenty‐seven figures; eight of them are drawings made from wax reconstructions of various stages.