Figures 8.3

Stylized tracheal system.
Figures 8.3. Stylized tracheal system.

(a) Oxygen uptake through invagination. (b) Invagination closed, with tracheal gas exchange through gill. 1, indicates point of invagination of the tracheal system; 2, indicates point for oxygen uptake; 3, indicates poi nt for oxygen delivery, such as muscles. (After Pritchard et al. 1993)

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  Reconstruction of Stenodictya lobata (Palaeodictyoptera: Dictyoneuridae).
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  Appendages of hypothetical primitive Palaeozoic (left of each diagram) and modern (right of each diagram) pterygotes (winged insects):