Cilium-like structures found by electron microscopy in the glandular and the small ductal lumina of the toad pancreas.

EKHOLM et al. (1962) and HERMAN et al. (1964) observed occasional circular formations which have an inner structure composed of one central and seven marginal annuli in glandular lumina and ductal lumina of rat pancreas. WINBORN (1963) also found the same structures in the glandular and in the intercalary ductal lumina of the Saimili monkey pancreas, and they thought these circular formations represent the cross-sections of the microvilli. In the toad pancreas the author also found the similar structures and made a few remarks on them in the previous paper (KOBAYASHI 1966). But, as it seemed that they might be in their ultrastructural properties different from the microvilli, since they contain internal annuli, the author has continued the electron microscope observations on them and obtained following important results which can clarify the nature of these structures