Abstract
This fish has sensory papillae on the skin of the head. These sensory papillae are easily detected as a whitish spot by the naked eye examination (fig. 1). Each papilla exhibits considerable variation in its size. In the specimen of 50 mm body-length, the papilla in the mid-size is about 0.2 mm in diameter in its base, 0.05 mm in diameter in its apex, and 0.08mm in its height. These papillae are arranged in definite lines in parallel with the long axis of the body: the pattern of arrangement of the papillae belongs to “the longitudinal type” named by AURICH (1938) (fig. 2 a, b). The histological structure of the papilla is shown in Fig. 3. The papilla projects prominent above the surrounding epidermis and has a dome-shape in its section. The specific cells with elongated pear-shaped form crowd closely in the outer portion of the papilla. These specifioc cells seem to be the sensory cells and be deprived of the cilia or sensory hairs. The specific cells are surrounded by extremely long cells which seem to be supporting cells. Each papilla is situated upon the corium which elevates upward the base of papilla and is penetrated by nerve fibres. These nerve fibres seem to reach to the above-mentioned specific cells, but the writer could not ascertain the relation between both. The writer's opinion about this question will be publised in accordance with hisfuture progress of investigation. It is interesting to note that these papillae seem to be generally prominent in such fishes as those equipped with poor canal line system.
