Figure legend

5,6. Two examples of a sinple pole. The centrosomes lie in a zone bounded by a concentric arrangement of endoplasmic reticulum(arrowheads). The spindle microtubules do not seem to emanate directly from the centrosome. x 30 000. Bar, 0.3 q.

Figure notes

The two crntrioles are regulary found to be of equal size. Mother and daughter centrioles lie at right angles (figs lb, 2b, 5) and can easily be iden- tified according to their respective geometrical position, as defined by Rieder and Borisy (1982). The centrioles show a classical diameter (-200 nm), but they have a short length (-200-250 nm),a characteristic of Drosophila. Mother and daughter centrioles exhibit doublet and triplet microtubules from their distal and proximal parts, respectively. No obvious link is detected between the two centrioles. The pericentriolar material is always faint. Surprisingly (see Discussion), this pericentriolar material is less dense in mitotic than in interphase cells.