Fig. 4. Sections through developing merozoites illustrating the route taken by micronemes from the Golgi body to the apex in relation to the subpellicular microtubules of the f-MAST. (A) Part of a merozoite transversely sectioned through the region of the vesicle budding zone at the periphery of the Golgi cisterna, an edge of which is visible in oblique section (go); three subpellicular microtubules are visible on the left (white arrows). Scale bar, 200 nm. (B) The microtubules of the f-MAST in transverse section (short arrows), close to micronemes (asterisk). The three membranes of the merozoite pellicle are also visible (long arrows); to the left of the merozoite surface is the membrane of the parasitophorous vacuole. (C) Structures similar to those in (B) with a more clearly defined microneme (asterisk). Scale bar for B and C, 100 nm. (D,E) Stereoscopic pair showing the apical region of a developing merozoite with migrating micronemes (black arrows) associated with a pair of subpellicular microtubules (white arrows) attached on the left to the polar rings (pr). Angle of tilt, 12°. Scale bar, 100 nm. (F,G) Another stereoscopic pair showing micronemes migrating in relation to a subpellicular microtubule (mt) attached to the apical polar rings (pr). The electron micrographs have been enhanced to show filamentous connections between the micronemes and microtubule (indicated by small arrows). Part of a rhoptry (rh) is also visible. Angle of tilt, 12°. Scale bar, 100 nm.