A Median section of a prehatching embryo (stage 32) stained with toluidine blue. The hatching gland cells (arrow) filled with many secretory granules (stained with dark color) are located in the upper and lower walls of the pharynx. Arrowhead, mouth opening; y, yolk; lj, lower jaw, pc, pharyngeal cavity; b, brain. B Median section of the pharynx region of a stage 36 embryo. High choriolytic enzyme was stained with polyclonal anti-high choriolytic enzyme antibody and tetraethylrhodamine isothiocyanate-conjugated anti-mouse immunoglobulin G. C Same section as in B. Low choriolytic enzyme was stained with monoclonal anti-low choriolytic enzyme antibody (B-34), biotin-conjugated anti-mouse immunoglobulin G, and avidin fluorescein isothiocyanate.