The mucosal epithelium of the oviduct in laying hens was studied by scanning electron microscopy. It was constructed principally by ciliated and nonciliated cells over its whole length. The distribution and appearance of these two types of epithelial cells varied considerably from one region of the oviduct to another. The infundibulum and the uterovaginal junction were characterized by the distribution of only ciliated cells having abundant, somewhat low cilia, different from any other region of the oviduct.
The spermatozoa introduced experimentally into the vagina were retarded and retained selectively in the lumina of these two regions of the oviduct. They were located among the cilia of ciliated cells. A barrier mechanism in the two regions against the spermatozoal transport through the oviduct in hens, which has been suggested by early workers, appeared to be a structural characteristic of the mucosal epithelium. The strong ciliary movement of the two regions may act as a simple mechanical barrier against the upward progress of spermatozoa and serve to make a "sperm nest" of these regions.