Fig. 4. Electron micrographs of unstained sections of the anterior sternal epithelium during late premoult after calcium oxalate loading experiments. (A) Example with larger and (B) with smaller calcium oxalate precipitates. (C,D) Details of calcium oxalate precipitates within smooth membranous cisternae (arrows). Scale bars, 1 µm in A and B; 0.5 µm in C and D. n, nucleus; cl, cuticular layer; m, mitochondria.