Fig. 1. Linear element morphologies and temporal comparison of cytological events in a time-course of the JB6 control strain. (A-D) Electron micrographs of spread and silver-stained nuclei of different linear element morphologies. (A) Single, short elements in a class I nucleus. Arrowheads indicate linear elements; `n' is the nucleolus. (B) Developing network in a class IIa nucleus. The arrow points at the spindle pole body (SPB), which is located close to the nucleolus (n). (C) Bundle in a class IIb nucleus. (D) Single, long elements in a class III nucleus. Bar, 1 µm. (E) Quantitation and temporal order of the different morphological classes. (F) Timing of cytological events as followed by DAPI staining. Horse-tail nuclei indicate meiotic prophase. Cells with more than one nucleus have progressed through the first meiotic division. After meiotic induction cells undergo a final mitotic division (peak at 1 hour) before they enter meiosis from G1 phase.