BrdU detection in sections of segmented worms after a 24 hour pulse. A, A', B, B' and C, C'. Transverse sections of early (A, B) and later (C) segments stained with anti-BrdU and DAPI. Arrow indicates genital primordia, and asterisks testis primordia. D. Sagittal section of early segmenting worm, showing last genital primordium (arrow) and the posterior non segmenting region. Anterior is to the right. E. Transverse section of the scolex. cp, cortical parenchyma; mp, medullary parenchyma; s, sucker; st, sub-tegument; t, tegument. Bars represent 50 μm except in D, 100 μm.