The development of Seessel's pouch in chick embryos was specifically focused on. This pouch was followed at stages between (13) and (28) of Hamburger and Hamilton (1351). This study bridges a gap in our knowledge, since many recent textbooks did not unfortunately describe this pouch. The histological techniques were used to describe the; morphological changes of the developing Seessel's pouch, and the histochemical techniques were used to add histochemical informations concerning the developmental dynamics of this pouch. Results showed that Beessel's pouch in this embryonic period grows rapidly in early stages, and rapidly involutes later on. Its rapid growth and mechanical affection by the ventral bending of the embryo was described. The fusion of Seessel 's and Rathke's pouches was documented in stages 16 to 19. The ventrally bending Seessel 's pouch was demonstrated to be continued to stage (17). after which dorsal deviation progressed rapidly resulting in separation of Seessel 's and Rathke's pouches (stage 20). A mass; of cells from the cranial portion of Seessel's pouch adhered to the dorsal wall of Rathke's pouch after the separation. This was discussed as a supportive finding to the suggestion of a possible contribution of entoderm to Rathke 's pouch. The histochemical investigation for sialic acid showed higher sialic acid at the cranial portion of Seessel's pouch than caudallv, with high invasivenes of this pouch's cells to the head mesenchyme and to Rathke's pouch. High concentration of uronic acid was found in the extracellular matrix of the head region, especially in a dense mesenchymal band extending between the natochord and the two pouches. This may have a role in maintaining tissue spaces and plays a role in the developmental events of Seessel's pouch.