Figure 11

Large, electron-opaque granules (G) in an early air sac (AS). Embryo, Centruroides gracilis. TEM. Cells with such granules as much as ~1 μm dia. are sometimes seen in the developing book lung tissue of embryos and first and second instars. These cells contribute cytoplasmic granular portions to the developing air sacs (Fig. 3). The result as shown here is a linear series of these granules that gradually become more lucent in their center. As shown in Figures 8, 9 and 10, small dense particles aggregate at the periphery of the cell fragments (F) as though an early stage in the formation of a continuous cuticular wall. The pale center of some large granules (G) suggests a similar movement of material toward the periphery where the separate fragments can fuse and form continuous cuticular walls on either side of the air channel (Figs. 12, 13, 14, 15, 16, 17). H, primordial hemolymph channel; N, nucleus. Scale, 2 um.