BrdU detection after a 4 hour pulse. A. Sagittal section of a tetrathyridium. The inset shows a general view of the same specimen. B. Whole-mount of early segmenting specimen showing periodic accumulations of BrdU+ cells (arrowheads). C. Early segments of whole-mount adult worm (lateral view) with early genital primordia (arrows). D. Later segment of whole-mount adult worm, with late genital primordium (arrow) and testis primordia (asterisks). E. Scolex and neck of adult worm; the broken line indicates the limit of the body wall. cp, cortical parenchyma; iml, inner muscle layer; mp, medullary parenchyma; s, sucker; st, sub-tegument; t, tegument. Note that the tegument was removed in whole-mount specimens. Bars represent 20 μm in A (200 μm in the inset), 50 μm in B, C and D, and 100 μm in E.