Figure 17

Presumptive primordial space holder across the hemolymph channel (H) of a second instar book lung. Centruroides gracilis. TEM. Many cells deteriorate in the primordial hemolymph channel (Figs. 12, 16), resulting in space for passage of hemolymph. The two intact cells (C) shown here make contact across the channel lumen. These may be precursor pillar cells for the pillar type space holders that earlier workers report are a common feature in the book lung hemolymph channels of adult scorpions and spiders [30, 45, 47–50]. AS, air sac; BT, bridging trabeculae; asterisk, non-bridging trabecula. Scale, 2 μm.