According to the internal structure and size of the granules, six types of nerve endings can be distinguished in the toad median eminence: 1. Endings containing mostly dense granules of 600 A in diameter; 2. Endings containing dense granules of about 800 A in diameter; 3. Endings which contain dense granules 1,000–2,000 A in diameter, with the peak at 1,200–1,400 A; 4. Endings containing granules with a characteristic structure, which differentiate them from the other three types; 5. Scarce endings containing granules 2,000 to 3,800 A in diameter; and 6. Endings containing only vesicles 400–500 A in diameter. Types 3 and 4 endings are mainly found in the outer pericapillary zone, and are probably responsible for the strong Gomori-positive reaction observed in this zone. The other four types of endings occur mainly in the inner pericapillary zone, and appear to be Gomori-negative.