The ciliature microtubules of Euplotes encysticus and their structural differentiation during asexual division, encystment and excystment were investigated by using FLUTAX staining and fluorescence microscopic techniques.(1) During morphogenesis, the close gathered kinetosomes of FVT-cirri become separated from each other, disintegrate and disappear gradually.The base bodies of dorsal cilia expand gradually and in the mean time the peripheral microtubules in basal bodies apart gradually from each other forming a plum blossom-like arrangement.Afterwards, the bands of granular cilia-anlagen occur in the corresponding cortical generating regions.(2) During encystment, AZM, PM, FVT-cirri and other organelles undergo a partial dedifferentiation process, i.e.with the condense of cell body, ciliatures aggregate each other at the ventral part of the spherical cyst cell body and the dorsal cilia arrange at the dorsal part with original pattern.(3) During excystment, the cell body swells as water is absorbed into the cell and becomes amoeba-like in shape.During this developmental stage, although weak fluorescence could be detected all over the cell, the fluorescence image of microtubules was never observed.The differentiated cell gets out of the cyst through a dorsal small pore of cyst wall and becomes a morphologically normal ciliate.Some tracks of dorsal cilia could be found at the dorsal part of the cyst wall left over during excystment. Based on the above results, following conclusions were suggested: during morphogenesis, the microtubules of ciliatures may have some contributions to the construction of new structures of the ciliate; during excystment, the microtubular structures have a further differentiating process, accompanying the differentiation of ameba-like shaped cell body.After these developmental events, all microtubules may go through a futher step of assembling and morphogenesis.