Ultrastructural studies of cilia formation during thyroid gland differentiation in grass snake embryos

► A sequence of cilia formation in thyroid of grass snake embryos has been described. ► Two waves of ciliogenesis and has been found. ► Two manners of cilia formation during thyroid differentiation can be identified. ► Ciliary appendages had been showed. ► Immotile cilia lacked central fibres had a 9 + 0 formula has been identified.