Abstract
A Japanese leech Hirudo nipponica was examined morphologically by means of the scanning electromicroscope. The most remarkable characteristics are as follows : The minute teeth or denticles had been described by many workers to arrange in " row" on each of the three jaws, but the present observation revealed that "the row" of teeth actually consisted of two rows of denticles and that there were occasionally observed leak, defect and deplacement of the denticles and disarray in the denticular arrangement. A great number of minute tubules are situated between the two rows of denticles, which seemed to be the openings of the salivary gland. The eyes are five pairs in number and concave on the surface, where a pore is observed in the center. Many minute pores are distributed on all the surface of jaw and body, especially abundantly near the annulus grooves and, further, on the inner surface of the anterior and posterior suckers. These minute pores are considered to be the orifice of the mucous gland or that of the excretory canal. The last annulus groove is wide and has a few folds. The penis has many small processes on the surface.
