MULLENIX: EIGHTH CRANIAL NERVE. 227 



IV. General Anatomy and Histology of the Ear of Fundulus. 



The anatomy of the ear of Fundulus conforms in a general way to 

 that of Perca fluviatalis and other teleosts, as described by Retzius 

 ('81^) in his monograph on the vertebrate ear. The external separa- 

 tion between utriculus and sacculus, however, is less marked than in 

 any species figured by him. Internally these divisions have a common 

 cavity, excepting at the anterior and posterior extremities, where the 

 utriculus is distinct. Anterior to the membrane which separates the 

 two divisions posteriorly there is a horizontal shelf, which projects into 

 the lumen of the ear, as shown in Figure 7 (Plate 2), and extends 

 anteriorly for a considerable distance. This may be regarded as 

 marking internally the boundary between uticulus and sacculus. 



The external anatomy of the ear is shown in Figures 1-3 (Plate 1), 

 and sections are shown in Figures 5-10 (Plate 2). I have followed 

 Retzius in nomenclature, excepting that for the semicircular canals I 

 have used the terms employed by Wiedersheim (;07). 



The wall of the labyrinth is composed everywhere of an outer base- 

 ment membrane, which is lined by an epithelial layer (Figs. 5-10, 

 Plate 2). In non-sensory regions this inner layer is very thin, and in 

 many Bielschowsky preparations it can scarcely be distinguished from 

 the basement membrane. In material stained by Mallory's (:05) 

 triple stain for connective tissue, however, it is easy to distinguish 

 the two layers; the basement membrane stains dark blue, and the 

 epithelium takes a lighter color, is obviously cellular in character, and 

 the nuclei of its cells are stained red. 



The topographical distribution of the sensory areas and the branch- 

 ing of the eighth nerve for their supply agree in Fundulus with the 

 account given by Retzius for other teleosts. In the sensorv areas the 

 epithelium is much thickened, being composed here of at least two 

 layers of cells, the small basal cells, next to the basement membrane, 

 and the large cylinder cells, which bear the sense hairs. Max Schultze 

 in 1858 described the sensory epithelium in the ear of fishes as com- 

 posed of basal cells and cylinder cells, with numerous nuclei between 

 them, surrounded by protoplasm and having prolongations upwards 

 and downwards, the former passing between the cylinder cells, and the 

 latter between the nuclei of the basal cells. These intermediate cells 

 he called the Fadenzellen. In subsequent publications Schultze 

 and others described similar elements in the auditory epithelium of 

 higher vertebrates. 



