During locust spermatocyte development, rudimentary cilia originate from all centrioles of the doubled prophasic centrosome, located in the centrosphere and specifically linked to the nuclear envelope. Membranous vesicles at the bases of the centrioles fuse to form an intracellular ampulla that contributes the ciliary membranes. Later in prophase the ampulla’s membrane is integrated into the plasma membrane so that all primary cilia project into the extracellular medium and lose contact with the nucleus. As the centrioles remain ciliated on their way to their polar positions, w e propose a mechanism for this migration which is based on this intimate association between centrosomes and plasma membrane, on membrane fluidity and on a contractile cell cortex. We noted a translocation of the ciliated centrioles below the cell surface at the metaphase/-anaphase transition which may be regarded as “deciliation” by light microscopy. Some possible explanations for the primary cilium’s role in cell cycle regulation are suggested.