Fig. 2. LEs as observed after silver staining in the electron microscope (EM) (top) and by immunostaining of Rec10 (bottom). The classification of LEs in the EM is according to Bähler et al. (Bähler et al., 1993). Nuclei containing many (up to >50) Rec10-po sitive spots (designated here as class Ia) appear inconspicuous in the EM. The empty nucleus in the EM (top left, class assignment not applicable) might correspond by its shape and size to immunostained class Ia. Classes I (Ib) and IIa are identified by both immunostaining and EM as containing individual threads and meshes of threads, respectively. Class IIb appears in the EM as bundles of LEs that probably correspond to the long, thick Rec10-positive structures. Silver-stained individual LEs of heterogeneous lengths, which prevail during later stages of meiosis (7-10 hours), were designated as class III (Bähler et al., 1993). The corresponding Rec10-LEs are classified as Ib. A class-Ib nucleus from a late time point in meiosis (8 hours in sporulation medium) is shown for comparison. Scale bar, 5 µm.