The Control of Respiratory Movements in Crustacea by Oxygen and Carbon Dioxide. II

1. The movements of the pleopods and of the epipodites of the maxillipedes of the stomatopod Squilla mantis are quickened by lack of oxygen and excess of carbon dioxide. 2. The rate of beat of the scaphognathite of the prawn Pandalus borealis is increased by oxygen lack and carbon dioxide excess. 3. The rate of movement of the scaphognathite of the shore crab Carcinus maenas is very irregular and is apparently independent of the gas content of the medium. 4. The rate of respiratory movements of the pleopods of the isopod Cirolana borealis is increased in low oxygen and high carbon dioxide tensions. 5. Both carbon dioxide excess and oxygen lack increase the rate of pleopod movement of the isopod Idotea neglecta, but the effect is not always permanent. Great individual variation is shown both in the threshold of response, and the extent of recovery. Carbon dioxide excess at first inhibits respiratory movements. 6. The isopods Anilocra physodes and Nerocila bivittata show no significant response to changes in the gas content of the medium.