Fig. 4. Mother centrioles with two daughters. Three examples of mother centrioles with two daughters. Each triplet is shown in two consecutive serial sections with a schematic to orient the reader. (A) A mother centriole (in the center) that is slightly angled with two longitudinal daughters, one to the left and the other to the right. (B) A mother in cross-section with two daughters, both in longitudinal section, one to the left and one (seen only in the section at the right) at the top. (C) A mother in cross-section with two longitudinal daughters, one to the right and the other to the left. Note that one of the daughters in each triplet is always longer than the other, suggesting that the two daughters were assembled at different times. Furthermore, note that the differences in the angle between the two daughter centrioles suggest that the initiation of a second daughter can occur at a variety of positions with respect to the first daughter. Bar, 100 nm.