3156. Respiratory system. 17 Color Photomicrographs. 1. Gill lamellae of Gammarus 2. Tracheal tubes of insect 3. Spiracle from insect 4. Clam gill, t.s. of gill filaments 5. Air chamber of snail (Helix) 6. Book or trachea lung of spider, l.s. 7. Gill of B