Abstract: The formation and function of centriole adjunct (CA) in spermatids of Locu sta migratoria and Coccinella septemgunctata are studied by electron microscopy with ultra-thin section and water spreading techniques. It is found that the CA is an electron dense body and the proacrosomal granule appear in the region between　the nucleus and the nebenkern. Later, the pre-centriole adjunct which mainly consists of 300A granules is attached to the nuclear membrane, of which the inner and outer components then become thickened. As the nebenkern differentiates into two mi tochondrial derivatives or a bit earlier, the proximal centriole migrates to the CA and is finally surrounded by the CA. As a basal body it is anchored on the nuclear envelope and the axoneme originates from it. Following the spermatid elonga tion, the shape of CA is progressively transformed and extended. The 250-300A chromatin fibers along the longitudinal axis of the spermatid are attached to the base of CA structure. As spermatid nucleus elongates, the chromatin fibers are unwound and join together to form ribbon structure. It is assumed that the CA is a transient organelle and its role is to organize the rearragement of chromatin in the spermatid and to direct the migration of the centriole to the nuclear region from thc place where the flagellum extends.

Key words: Locusta migratorta manilensts——Coccinella septempunctata., centriole adjunct——spermatid'