Figure 14

Formation of space holders by extension of cell processes (Pr) into the lumen of the developing air sacs (AS). First instar, Centruroides gracilis. TEM. Cells adjacent to the air sac wall contain many vesicles (V) and granules (G) that are apparently components for the thickening cuticular wall (Cu). The cell processes (trabeculae) also contain vesicles and granules so apparently the protrusions can gradually enlarge and extend across the lumen, forming wall-to-wall (bridging) space holders (e.g., Figs. 15, 16, 17). H, primordial hemolymph channel. Scale, 1 μm.