Figure 4: Histological, histochemical analysis of the undifferentiated stage. Figure 4A: The wall of the caudal portion of the oviduct at day of hatching formed of simple columnar epithelium (Ep), rested on undifferentiated tunics (asterisk). (H & E). Figure 4B: Semithin section of the caudal portion at the day of hatching showing simple columnar epithelium (arrowhead) rested on undifferentiated mesenchymal stroma (asterisk). (TB). Figure 4C: General view of caudal portion at 10- days showing numerous short mucosal folds. (H &E). Figure 4D: In semithin section, the epithelium at 10- days is formed of simple columnar cells, with many mitotic divisions in the epithelium and stroma (arrowheads). (TB). Figure 4E: General view of the caudal portion of the oviduct at 20-days old. (H & E). Figure 4F: In semithin section of the caudal portion at 20-days old, the epithelium consisted of ciliated (cc) and secretory cells (sc). The muscle layer differentiated into inner circular and outer longitudinal smooth muscle fibers (Ms). (TB). Figure 4G: The epithelium at 20-days showing negative reaction by PAS (arrowhead). Figure 4H: Crossmon's Trichrome showing abundant collagenous fibers, which were extended into the folds.