Transverse tomographic (A-B) and histological sections (C) displaying the Poecilia saccule, its otolith and the corresponding macula. The histological section (C) is from the inner ear of Poecilia mexicana. The higher resolution tomographic section in (B) shows that the nerve (VIII), otolith, and macula of the saccule could effectively be discriminated. For identification of the delimitations of the macula, the clearly visible sulcus of the otolith in the tomographic sections could be used; the sulcus is the furrow on the medial face of the saccular otolith housing the macula sacculi. Despite better discrimination of the macula from overlying otolithic membrane and the underlying basal lamina in the histological section, delimitations are still difficult to identify because of the gradual transition of the macula into non-sensory epithelium and the few organic remains of the dissolved otolith. In the insert in (B) and in (C) the sulcus is indicated by a dotted line and the macula is red labeled. Ce, cerebellum; ms, macula sacculi; VIII, part of the VIIIth cranial nerve innervating the macula sacculi. Scale bars, 500 μm.