Electron micrographs of the walls of oocysts and sporocysts undergoing various treatments. A bar represents 1 μm in A and 100 nm in the other micrographs. (A) Section through an intact oocyst showing the two collapsed sporocysts (Sp). OW – oocyst wall. (B) Detail of an untreated oocyst showing the outer (Oo) and inner (Oi) layers of the oocyst wall. (C) Detail of an untreated oocyst showing the outer (So) layer and the plates of the inner (Si) layer of the sporocyst wall connected by a thicken suture (S). (D) Enlargement of a heat-treated oocyst showing the retention of both the outer (Oo) and inner (Oi) layers oocyst wall. (E) Enlargement of a heat-treated oocyst showing the retention of both the outer (So) and inner (Si) layers of the sporocyst wall. (F) Detail of the wall of an oocyst after treatment with bleach showing the inner (Oi) layer, but loss of the outer layer of the oocyst wall. (G) Bleach-treated intact oocyst showing the retention of both the outer (So) and inner (Si) layer of the sporocyst wall. (H) Naked sporocyst treated with bleach showing the loss of the outer layer, but retention of the inner (Si) layer of the sporocyst wall. S – suture. (I) Detail of an oocyst treated with bleach and heating showing the inner (Oi) layer, but loss of the outer layer of the oocyst wall. (J) Bleach and heat treated intact oocyst showing the retention of both the outer (So) and inner (Si) layer of the sporocyst wall. (K) Naked sporocyst treated with bleach and heating showing the loss of the outer layer, but retention of the inner (Si) layer of the sporocyst wall. S – suture.